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To use optical modeling to compare a 6.0 mm and 7.0 mm intraocular lens (IOL) optic diameters on peripheral retinal illumination with implications for negative dysphotopsia.Mayo Clinic, Rochester, Minnesota, and Simpson Optics LLC, Arlington, Texas.Model eye.Ray-tracing software was used to simulate retinal illumination from an extended light source for a pseudophakic eye with in-the-bag biconvex IOLs (refractive index [n] = 1.46 and 1.55) and a 2.5 mm pupil. Ray-tracing diagrams and simulated retina illumination profiles were compared using the 6.0 mm and 7.0 mm optic diameter IOLs. Retinal locations were scaled to relative visual angles from 70 to 110 degrees horizontally.A 7.0 mm optic (n = 1.46) expands the image field by 2.8 degrees compared with a 6.0 mm optic. High-angle input light misses a 7.0 mm optic at a larger visual angle than a 6.0 mm optic, shifting illumination of the peripheral retina by this light anteriorly by 5.6 degrees. Consequently, a region of nonilluminated peripheral nasal retina is enlarged and shifted peripherally using a 7.0 mm optic (visual angle, 86.3 to 96.3 degrees) compared with a 6.0 mm optic (visual angle, 83.5 to 90.7 degrees). Similar illumination changes were seen modeling a 1.55 n IOL.A narrow dark region in the nasal retina when using a 6.0 mm optic is changed to a broader, more peripheral dark region when using a 7.0 mm optic. An extended, more peripheral dark nasal region may make a temporal shadow less bothersome and explain lower negative dysphotopsia rates using a 7.0 mm optic.

Goal-directed eye movements (saccades) bring peripheral objects of interest into high-acuity foveal vision. In preparation for the incoming foveal image, the perception of the saccade target may sharpen gradually before the eye movement is executed. Indeed, previous studies suggest that pre-saccadic attention shifts enhance sensitivity to high spatial frequencies (SFs) more than sensitivity to lower SFs. This pattern, however, was observed within a narrow frequency range and may reflect local changes in the shape of a broader underlying sensitivity profile. Depending on the development of the profile's shape, SFs above the previously examined range may profit less from saccade preparation. To assess the impact of saccade preparation on the shape of a broader sensitivity profile, we prompted observers to discriminate the orientation of a sinusoidal grating (the probe) presented briefly at the target of an impending saccade, at 10 dva (degree of visual angle) eccentricity. The probe's SF ranged from 1 to 5.5 cycles per dva (cpd) and was unpredictable on a given trial. We fitted observers' response accuracies across SFs with a log-parabolic, that is, inverted U-shaped function. Long before saccade onset, the profile peaked at .6 cpd and dropped off towards lower and higher SFs with broad bandwidth. During saccade preparation, the peak of the profile increased and shifted towards higher SFs while the bandwidth of the profile decreased. As a consequence of this reshaping process, pre-saccadic enhancement increased with SF up to 2.5 cpd, corroborating previous findings. Sensitivities to higher SFs, however, profited less from saccade preparation. We conclude that the extent of pre-saccadic enhancement to a particular SF is governed by its position on a broader sensitivity profile which reshapes substantially during saccade preparation. The shift of the profile's peak towards higher SFs increases resolution at the saccade target even when the features of relevant visual information are unpredictable.

Made available in DSpace on 2022-05-01T10:35:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 Vision is crucial for humans to interact with their surrounding environment, and postural sway is reduced to allow short eye movements. However, the extent of subtle changes in postural control for horizontal and vertical eye movements remains unclear. The goal of this study was to investigate the effects of vertical and horizontal eye movements on head and trunk control in young adults. Fifteen healthy adults (23.4 ± 4.7 years) stood upright in three conditions for 60 s: fixation, horizontal, and vertical guided eye movements. In fixation, participants had to fixate on a stationary target. In both the horizontal and vertical eye movements, the target was presented with a frequency of 0.5 Hz and a visual angle of 11°. Eye displacement was monitored using a SMI eye tracker (ETG2.0) and trunk and head sway were monitored using infrared markers (Optotrak 3020, NDI). The mean sway amplitude was lower in both directions for eye movements and lowest in the vertical direction compared to the fixation condition. The sway area was also lower in vertical eye movement than in the fixation condition. We also found that the sway reduction was greater at head than at trunk level. The median frequency sway in the anterior–posterior direction was higher in both eye movements than in fixation. Based upon these results, we suggest that to perform short eye movements, postural sway is more strongly controlled at the head level than at the trunk and in vertical eye movements than in horizontal movements. Institute of Biosciences São Paulo State University, SP Institute of Physical Activity and Sport Science Cruzeiro do Sul University, SP Univ. Lille CNRS UMR 9193 - SCALab - Sciences Cognitives et Sciences Affectives Departmento de Educação Física Instituto de Biociências Universidade Estadual Paulista, Av. 24-A, 1515, SP Institute of Biosciences São Paulo State University, SP Departmento de Educação Física Instituto de Biociências Universidade Estadual Paulista, Av. 24-A, 1515, SP

In order to extract the relationship between head-eye movements and visual impressions while using Head-mounted displays (HMD) to view images, two types of response task experiments involving visual stimuli were conducted, using several visual angles. Both head movements and visual impressions increased with the visual angles during the observation of moving visual stimuli. Vestibulo-ocular reflex (VOR) gains as a ratio of eye and head movements decreased as the visual angle increased because the eye movement deviations were relatively small. When the viewer’s reaction required an action, such as rotating the head or aiming at a target, the strength of the viewer’s impression increased, though VOR gains remained at the same level.

Purpose To evaluate negative dysphotopsia in the far periphery of the pseudophakic eye by generating simulated images of text charts. Setting Consultancy. Design Laboratory study. Methods Simulated images of a peripheral text chart were created using a ray-trace model of a pseudophakic eye. The point spread function varies strongly with a radial location. Retinal angles subtended at the second nodal point were used to linearly scale retinal locations to a polar plot in object space, weighting rays by the object luminance, the total transmittance, and a cosine normalization for pupil effects. Improved scaling using a phakic 70-year-old eye was also explored. Results Images demonstrate a distinct shadow with a 2.5 mm pupil between the upper limit of the text image formed by the intraocular lens (IOL) and a second larger image due to light missing the IOL. The shadow is rapidly softened by a small increase in pupil diameter. Conclusions The images verified characteristics that previously were only inferred indirectly: (1) With a 2.5 mm pupil, there is a prominent dark shadow. (2) Light missing the IOL experiences lower power and forms a larger image and also comes from a lower visual angle. (3) A small increase in pupil diameter causes the shadow to fade. The calculations showed that imaging in the far periphery is very different for the pseudophakic eye in comparison with the phakic eye. The limit of the focused image is probably the primary cause of the shadow, yet relatively few patients find this to be bothersome.

BACKGROUND The visual prognosis in Leber hereditary optic neuropathy (LHON) is generally poor. However, some individuals can have spontaneous visual recovery (VR) in one or both eyes by a mechanism that is not yet clearly understood. The purpose of this study was to determine whether certain clinical and optic disc features are associated with VR in patients with LHON. METHODS We retrospectively examined 80 eyes of 40 patients with LHON using clinical databases, fundus photographs, and high-definition spectral-domain optical coherence tomography (OCT) images. VR was defined as a gain of 3 or more lines of logarithm of the minimum angle of resolution (logMAR)-scaled visual acuity from nadir; this represents a doubling of the visual angle. Patients were divided into VR and nonrecovery (NR) groups. Using fundus photographs, we measured optic disc size and evaluated for the presence of optic disc features, including peripapillary telangiectasia, disc hyperemia, and swelling. We also measured the disc area, cup-to-disc ratio, and rim area of the optic disc using OCT. RESULTS Twenty-one of 80 eyes (26%) had a VR. The VR occurred within 2 years after onset in 81% of cases. The VR group showed younger age at onset (21 vs 29 years, P = 0.017) and better visual acuity at the nadir (1.39 vs 2.16 logMAR, P < 0.001) compared with the NR group. Optic disc features, particularly peripapillary telangiectasia (P = 0.027) and disc hyperemia (P = 0.006), were more prominent in the NR group. The cup-to-disc ratio was significantly smaller (0.64 vs 0.71, P = 0.004) and the rim area was significantly greater (1.17 vs 0.85 mm, P < 0.001) in the VR group compared with the NR group. CONCLUSIONS A younger age at onset and a less severe reduction of visual acuity at the nadir were associated with a higher probability of VR. Presence of peripapillary telangiectasia and optic disc hyperemia may serve as predictive factors for poor visual prognosis in patients with LHON.

While online experiments have shown tremendous potential to study larger and more diverse participant samples than is possible in the lab, the uncontrolled online environment has prohibited many types of psychophysical studies due to difficulties controlling the viewing distance and stimulus size. We introduce the Virtual Chinrest, a method that measures a participant’s viewing distance in the web browser by detecting a participant’s blind spot location. This makes it possible to automatically adjust stimulus configurations based on an individual’s viewing distance. We validated the Virtual Chinrest in two laboratory studies in which we varied the viewing distance and display size, showing that our method estimates participants’ viewing distance with an average error of 3.25 cm. We additionally show that by using the Virtual Chinrest we can reliably replicate measures of visual crowding, which depends on a precise calculation of visual angle, in an uncontrolled online environment. An online experiment with 1153 participants further replicated the findings of prior laboratory work, demonstrating how visual crowding increases with eccentricity and extending this finding by showing that young children, older adults and people with dyslexia all exhibit increased visual crowding, compared to adults without dyslexia. Our method provides a promising pathway to web-based psychophysical research requiring controlled stimulus geometry.

It is still unclear whether size constancy is an innate ability or whether it develops with age. As many developmental studies are limited to the child’s comprehension of the task instructions, here, an implicit measure of perceived size, namely, simple manual reaction time (RT), was opted for based on the assumption that perceptually bigger objects generate faster detection times. We examined size constancy in children (from 5 to 14 years of age) and adults using a simple RT approach. Participants were presented with pictures of tennis balls on a screen that was physically moved to two viewing distances. Visual stimuli were adjusted in physical size in order to subtend the same visual angle across distances, determining two conditions: a small-near tennis ball vs. a big-far tennis ball. Thanks to size constancy, the two tennis balls were perceived as different even though they were of equal size on the retina. Stimuli were also matched in terms of luminance. Participants were asked to react as fast as possible to the onset of the stimuli. The results show that the RTs reflected the perceived rather than the retinal size of the stimuli across the different age groups, such that participants responded faster to stimuli that were perceived as bigger than those perceived as smaller. Hence, these findings are consistent with the idea that size constancy is already present in early childhood, at least from the age of five, and does not require extensive visual learning.

Visual dysfunction in patients with macular hole is believed to occur because of cone cell displacement, often measured by the Watzke-Allen test (WAT). However, it is unknown if the horizontal and vertical measurements recorded by WAT reflect the true extent of photoreceptor displacement. This study aimed to measure the extent of photoreceptor displacement in patients with macular hole using WAT and compare the displacement value with the hole diameter measured by optical coherence tomography (OCT). This prospective, observational study at a single tertiary referral center included 43 patients with macular hole. WAT thresholds were assessed for their ability to detect macular hole. The slit was presented vertically and horizontally, and the brightness of the monitor screen was 180 cd/m2. Horizontal and vertical WAT thresholds for distortion were measured. Correlations and performance evaluations were assessed by Pearson's correlation analysis and Wilcoxon rank-sum test, respectively, between WAT threshold values and hole diameters. Horizontal and vertical WAT thresholds and diameters were compared using paired t-tests. The mean vertical WAT threshold (1.95° ± 0.87°) was significantly higher than the mean horizontal threshold (1.71° ± 0.73°; P < 0.0001). The mean minimum horizontal hole diameter (303.42 ± 111.16 mm; visual angle, 1.01°) was significantly greater than the mean minimum vertical diameter (264.12 ± 107.88 mm; visual angle, 0.88°; P = 0.0149). The minimum vertical and horizontal macular hole diameters were positively correlated with the vertical and horizontal WAT threshold values (r = 0.514, P < 0.01; r = 0.447, P < 0.01, respectively). The WAT threshold values were greater than the respective minimum macular hole diameters, indicative of cone cells displacement over an area larger than that of the hole. The difference in the extent of vertical and horizontal distortions suggests asymmetric hole formation. Hence, WAT threshold values may help evaluate visual function in patients with macular hole., Macular hole; Optical coherence tomography; Photoreceptors; Watzke-Allen test.

A patient suffering from visuo-spatial neglect was investigated as a special interest case during a study on the effectiveness of "restorative approaches" after visual field loss. This patient trained with our newly developed Virtual Reality (VR) system "Salzburg Visual Field Trainer" for 254 days. Perimetric results show a visual field expansion of 48.8% (left eye) and 36.8% (right eye) translating to an improvement of approximately 5.5° to 10.5° of visual angle. Further, subjective self-report shows improvements of up to 317% in visual field functionality. Our results indicate that patients suffering from visuo-spatial neglect could benefit from a VR-based restorative intervention.

Rationale: Among the serious consequences of alcohol use disorder (AUD) is the reduced ability to process visual information. It is also generally agreed that AUD tends to occur with disturbed excitation–inhibition (EI) balance in the central nervous system. Thus, a specific visual behavioral probe could directly qualify the EI dysfunction in patients with AUD. The tilt illusion (TI) is a paradigmatic example of contextual influences on perception of central target. The phenomenon shows a characteristic dependence on the angle between the inducing surround stimulus and the central target test. For small angles, there is a repulsion effect; for larger angles, there is a smaller attraction effect. The center-surround inhibition in tilt repulsion is considered to come from spatial orientational interactions between orientation-tuned neurons in the primary visual cortex (V1), and tilt attraction is from higher-level effects of orientation processing in the visual information processing.Objectives: The present study focuses on visual spatial information processing and explores whether chronic AUD patients in abstinence period exhibited abnormal TI compared with healthy controls.Methods: The participants are 30 male volunteers (20–46 years old) divided into two groups: the study group consists of 15 clinically diagnosed AUD patients undergoing abstinence from alcohol, and the control group consists of 15 healthy volunteers. The TI consists of a center target surround with an annulus (both target and annulus are sinusoidal grating with spatial frequency = 2 cycles per degree). The visual angle between center and surround is a variable restricted to 0°, ±15°, ±30°, or ±75°. For measuring the TI, participants have to report whether the center target grating orientation tilted clockwise or counterclockwise from the internal vertical orientation by pressing corresponding keys on the computer keyboard. No feedback is provided regarding response correctness.Results: The results reveal significantly weaker tilt repulsion effect under surround orientation ±15° (p < 0.05) and higher lapse rate (attention limitation index) under all tested surround orientations (all ps < 0.05) in patients with chronic AUD compared with health controls.Conclusions: These results provide psychophysical evidence that visual perception of center-contextual stimuli is different between AUD and healthy control groups.

Visual-angle has been used as the conventional unit to determine the field-of-view (FOV) in traditional fundus photography. Recently emerging usage of eye-angle as the unit in wide field fundus photography creates confusion about FOV interpretation in instrumentation design and clinical application. This study aims to systematically derive the relationship between the visual-angle θv and eye-angle θe, and thus to enable reliable determination of the FOV in wide field fundus photography. FOV conversion ratio θe/θv, angular conversion ratio Δθe/Δθv, retinal conversion ratio Δd/Δθv, retinal distance and area are quantitatively evaluated. Systematic analysis indicates that reliable conversion between the θv and θe requires determined nodal point and spherical radius of the eye; and the conversion ratio is not linear from the central field to peripheral region. Based on the eye model with average parameters, both angular conversion (Δθe/Δθv) and retinal conversion (Δd/Δθv) ratios are observed to have a 1.51-fold difference at the central field and far peripheral region. A conversion table, including θe/θv, Δθe/Δθv, Δd/Δθv, retinal area and percentage ratio, is created for reliable assessment of imaging systems with variable FOV.

Biometric identification using eye movements is an identification method with low risk of spoofing, however the problem with it is that the eye movement measurement time is long. In this paper, we studied pattern lock authentication using eye movement features. As a result of 1-to-N identification using the data of six subjects, it was found that the identification rate was maximized at a measurement time of 3 seconds, indicating that it was possible to identify individuals in a short measurement time. In addition, we examined the effects of the data measurement time conditions and the presentation size on the rate of identification. The condition which maximized the identification rate was a measurement time limit of 3 seconds or the presentation of a stimulus pattern using a visual angle of 27.20°. Furthermore, the Mel-Frequency Cepstral Coefficient (MFCC) of the viewpoint coordinates and the diameter of the pupil were the features that contributed most to identification.

ObjectiveStudies on neuropsychological rehabilitation of visual field defects provide an inconsistent picture regarding the effectiveness of so-called “restorative approaches” in visual field recovery (VFR). During a current research project on the clinical evaluation of VFR - in combination with head mounted virtual reality displays (HMD) - a patient (“Patient 7”) suffering from visual neglect was investigated. Although the concept of VFR is originally not intended for patients suffering from higher cortical regions (as in neglect), we hypothesized that due to the strong attention-demanding training situation in HMDs, neglect patients might benefit from these intervention procedures based on restorative approaches.Methods and AnalysisPatient 7 was examined perimetrically using a “Humphrey Field Analyzer”, “Goldmann Perimetry” and our newly developed and validated eye-tracking supported perimetric methodology “Eye tracking based visual field analysis” (EFA). Based on these high resolution results from the EFA, the exact location of the transition area between intact and defect visual field of Patient 7 was assessed. Next, bright light stimuli were placed along this area in our newly developed HMD “Salzburg Visual Field Trainer” (SVFT). The aim was to stimulate neuroplasticity - according to the concept of restitutive approaches - in the corresponding cortical areas of the patient. Patient 7 trained with the SVFT for a time period of 254 days. In 6 appointments the objective and subjective rehabilitation progress was assessed.ResultsPerimetric assessment with the EFA shows an expansion of Patient 7’s visual field of 48.8% (left eye) and 36.8% (right eye) after 254 days of training with the SVFT. Individual areas in the patient’s visual field show a visual improvement of approximately 5.5° to 10.5° of visual angle. Subjective self-report of Patient 7 additionally shows improvements in self-evaluation of up to 317% in visual field functionality compared to self-evaluation on the first assessment date.ConclusionsThe results from Patient 7 indicate that patients suffering from visual neglect potentially benefit from a neuropsychological intervention with HMD based on the restorative concept of visual field recovery. However, further studies with large case numbers and a focus both on daily-life improvements and on a clear distinction between patients with lesions in earlier and higher cortical areas are needed to make empirically valid and generalizing statements about our findings.

The present study examined whether luminance values of an edge between regions affect figure-ground perception. A dark-gray or light-gray region was presented on the left (or upper) or right (or lower) side of an edge. Observers reported which region was perceived as a figure. The results in the 0.2° edge width condition showed that dark-gray regions with low luminance edges were perceived as a figure significantly more often than dark-gray regions with high luminance edges. The edge luminance effect occurred, partly occurred, and did not occur when the edge widths were 0.2, 0.5, and 0.8° of visual angle, respectively. These results showed that luminance values of the edge between the regions affected figure-ground perception, and that regions with luminance values closer to that of the edge between the regions were perceived as a figure more often, but only when the edge width was narrow. The edge luminance effect occurred less often as the edge width was increased and would be attributed to similarity grouping between edge and region.

Objective: We present a new type of brain-computer interface (BCI) that utilizes the retinotopic mapping of motion-onset visual evoked potentials (mVEP) to accomplish four control channels using a single motion stimulus. Methods: Participants selected a BCI command by fixating one of four target locations around a centrally presented visual motion stimulus. A template-matching method was employed to recognize the users’ intention by decoding the position of the motion stimulus in the peripheral visual field, and classification performances were evaluated in an offline manner. The motion stimulus eccentricity between the targets and the visual motion stimulus varied among 5.1°, 6.7°, 9.8°, and 13.0°. Results: Distinct N200 spatial patterns were elicited when participants directed attention overtly to the target locations. A four-class classification accuracy of 72.2 ± 5.05% was achieved with a distance of 5.1° visual angle between the targets and the visual motion stimulus. The classification accuracies decreased with increasing motion stimulus eccentricities but remained separable well above the chance level at 13.0° (47.3 ± 8.54%). Conclusion: Our results support the feasibility of a single-stimulus, multitarget mVEP BCI. Significance: The proposed system can simplify the visual stimulation of mVEP BCIs, improve user experience and pave the way for simple yet efficient BCI communication.

To investigate the functional integrity of visual pathway in hypothyroid patients by pattern visual evoked potential (PVEP). We enrolled 36 female patients with history of hypothyroidism (18 overt and 18 subclinical) aged 20 to 60 years and 36 healthy women of similar age (control group). All subjects had a complete ophthalmic examination. For VEP testing, subjects were exposed to checks subtending a visual angle of 15 and 60 min of arc. For the 15 min of arc check size, the mean P100 latency was significantly delayed (113 milliseconds (ms)) and amplitude significantly reduced (9.2 microvolts (µv)) in the hypothyroidism group compared with controls (109.6 ms and 11.6 µv, respectively). For this 15′ check size, the group differences were related to significantly increased latency and reduced amplitude of responses in the group with overt hypothyroidism compared with controls. There was no difference between the groups (hypothyroid vs control) with 60 min of arc check size. There was a significant correlation between severity of the disease and PVEP component. In conclusion, low levels of circulating hypothyroid hormone are associated with delay in the pattern VEP to small check sizes. This CNS involvement worsens in patients with greater severity and duration of hypothyroidism.

The existence of a cortical “attentional filter” in the form of spatially selective modulation of alpha power (8-14 Hz) is a dominating hypothesis in electrophysiological studies. During auditory spatial attention hemipsheric lateralized posterior alpha modulations have been reported leading to the generalization of this hypothesis. Typically, this pattern is interpreted as reflecting a top-down endogenous mechanism for suppressing distracting input from unattended directions of sound origin. The present study on auditory spatial attention rejects this interpretation by demonstrating that alpha power modulation is closely linked to oculomotor action. Towards this end, we designed an auditory paradigm in which participants were required to attend to upcoming sounds from one of 24 loudspeakers arranged in a horizontal circular array around the head. Maintaining the location of an auditory cue was associated with a topographically modulated distribution of posterior alpha power resembling the findings known from visual attention. Multivariate analyses allowed the prediction of the sound location in the horizontal plane. Importantly, this prediction was also possible, when derived from signals capturing saccadic activity. Using eye tracking, two control experiments on visual (N=122) and auditory (N=10) spatial working memory confirmed that, in absence of any visual/auditory input, lateralization of alpha power is linked to lateralized gaze direction (± 3° visual angle). Attending to an auditory stimulus engages oculomotor and visual circuits in a topographic manner akin to the retinotopic organization in vision. We conclude that allocation of spatial attention is not sufficient to account for alpha lateralization without consideration of gaze control.

Comment: Main manuscript contains 5 figures plus 2 tables. SI contains 2 tables, Visual translation tolerance refers to our capacity to recognize objects over a wide range of different retinal locations. Although translation is perhaps the simplest spatial transform that the visual system needs to cope with, the extent to which the human visual system can identify objects at previously unseen locations is unclear, with some studies reporting near complete invariance over 10{\deg} and other reporting zero invariance at 4{\deg} of visual angle. Similarly, there is confusion regarding the extent of translation tolerance in computational models of vision, as well as the degree of match between human and model performance. Here we report a series of eye-tracking studies (total N=70) demonstrating that novel objects trained at one retinal location can be recognized at high accuracy rates following translations up to 18{\deg}. We also show that standard deep convolutional networks (DCNNs) support our findings when pretrained to classify another set of stimuli across a range of locations, or when a Global Average Pooling (GAP) layer is added to produce larger receptive fields. Our findings provide a strong constraint for theories of human vision and help explain inconsistent findings previously reported with CNNs.

ObjectiveSeveral studies report evidence for training-related neuroplasticity in the visual cortex, while other studies suggest that improvements simply reflect inadequate eye fixation control during perimetric prediagnostics and postdiagnostics.Methods and analysisTo improve diagnostics, a new eye-tracking-based methodology for visual field analysis (eye-tracking-based visual field analysis (EFA)) was developed. The EFA is based on static automated perimetry and additionally takes individual eye movements in real time into account and compensates for them. In the present study, an evaluation of the EFA with the help of blind spots of 58 healthy participants and the individual visual field defects of 23 clinical patients is provided. With the help of the EFA, optical coherence tomography, Goldmann perimetry and a Humphrey field analyser, these natural and acquired scotomas were diagnosed and the results were compared accordingly.ResultsThe EFA provides a SE of measurement of 0.38° for the right eye (OD) and 0.50° for the left eye (OS), leading to 0.44° of visual angle for both eyes (OU). Based on participants’ individual results, the EFA provides disattenuated correlation (validity) of 1.00 for both OD and OS. Results from patients suffering from cortical lesions and glaucoma further indicate that the EFA is capable of diagnosing acquired scotoma validly and is applicable for clinical use.ConclusionOutcomes indicate that the EFA is highly reliable and precise in diagnosing individual shape and location of scotoma and capable of recording changes of visual field defects (after intervention) with unprecedented precision. Test duration is comparable to established instruments and due to the high customisability of the EFA, assessment duration can be shortened by adapting the diagnostic procedure to the patients’ individual visual field characteristics. Therefore, the saccade-compensating methodology enables researchers and healthcare professionals to rule out eye movements as a source of inaccuracies in pre-, post-, and follow-up assessments.

Made available in DSpace on 2022-04-28T19:46:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This study investigated the modulation of center of pressure (CoP) displacements of young adults as they performed predictable and unpredictable saccadic eye movements in stationary and moving visual scenarios. We also examined whether the relationship between CoP displacements and visual stimulus, provided by the moving scenario, and gaze control itself, are affected by the demands of the saccadic tasks. Fifteen young adults (20.53 ± 2.1 years old) stood upright on a force plate, inside a moving room, wearing an eye tracker while performing three tasks: gaze fixation (fixating on a target in the center of the screen), predictable task (saccades while following a target which continuously appeared and disappeared on the right and left sides), and unpredictable task (similar to the previous task, but the participants did not know which side the target would appear on). For saccadic tasks, the target appeared at a frequency of 1.1 Hz and with eccentricity of 11.5 degrees of visual angle. Two blocks of six trials were performed: in the first block, the room remained stationary and in the second, it oscillated (0.6 cm amplitude; 0.2 Hz frequency). Mean amplitude of CoP displacements was lower in the saccadic tasks compared to the gaze fixation, in both conditions; and higher in the moving scenario than in the stationary condition. Variability of CoP displacements was lower in the unpredictable saccades than gaze fixation task. Saccade reaction time was longer in the unpredictable than predictable task. We conclude that CoP displacements are reduced to facilitate performance of the saccadic tasks regardless of conditions and task complexity. Furthermore, lower variability suggests modulation of CoP displacements to deal with the increased attentional demands associated with the performance of the unpredictable saccades, indicating the important role of visual task constraints in postural control. São Paulo State University (UNESP) Department of Physical Education Faculty of Sciences Laboratory of Information Vision and Action (LIVIA) Post-graduation Program in Movement Sciences São Paulo State University – UNESP Centro Universitário Sagrado Coração (UNISAGRADO) Department of Health Science São Paulo State University (UNESP) Department of Physical Education Faculty of Sciences Human Movement Research Laboratory (MOVI-LAB) São Paulo State University (UNESP) Department of Physical Education Institute of Bioscience Movement Studies Laboratory (LEM) São Paulo State University (UNESP) Department of Physical Education Faculty of Sciences Laboratory of Information Vision and Action (LIVIA) Post-graduation Program in Movement Sciences São Paulo State University – UNESP São Paulo State University (UNESP) Department of Physical Education Faculty of Sciences Human Movement Research Laboratory (MOVI-LAB) São Paulo State University (UNESP) Department of Physical Education Institute of Bioscience Movement Studies Laboratory (LEM)

Purpose Covert spatial attention directs the attentional spotlight to a particular part of the visual field and modulates the retinotopic organized oscillatory brain activity. This study aimed to investigate the electrophysiological characteristics of oscillatory brain activity when simulating different defect degrees of the central visual field. Methods The power of theta and alpha activity was extracted using time-frequency analysis in forty healthy participants enrolled in the three-stimulus oddball paradigm. Standard stimuli were black-and-white checkerboards. Target stimuli simulated different degrees of the central visual field defect by superimposing black discs with different radii (5, 10, 20, and 30 degrees of visual angle) on the center of the peripheral checkerboard stimulation, and distractor stimuli presented in the reverse form with a constant radius. Results By simulating central visual field defects, the increased theta power and decreased alpha power was observed when detecting target stimuli. Besides, the magnitude of increased theta power and decreased alpha power peaked at the 10-degree defect conditions, and gradually decayed to the 5 and 30-degree defect conditions, which separately indicated two key points in the visual field through the spatial attentional modulations. Conclusion Using cortical oscillatory dynamics in the time-frequency platform, the defect category of the central visual field could be quantified by alpha and theta oscillations in power differences. These findings suggest that cortical oscillations are sensitive markers for the discrimination of gradient effects of the central visual field defects and further demonstrate the phenomenon of functional dissociation in the visual field in covert spatial attention status.

Objective The Argus I implant is a first-generation epiretinal prosthesis approved for an investigational clinical trial in the U.S. Its successor, the Argus II implant, has a higher electrode density for increased spatial resolution and covers a larger retinal area to accommodate a wider visual angle. Both generations of Argus restored some vision to end-stage RP patients, but it remains unclear how the increased electrode count affected the visual percepts. Here we report a study of the first person on earth with two 'bionic eyes', with an Argus I implanted in one eye and Argus II in the other, to compare the retina-electrode interface and the visual outcome of the two devices. Approach The retina-electrode interface was examined by electrode impedance, perceptual threshold, and ophthalmic images such as ocular coherence tomography data and fundus imaging. The subject's visual outcomes were evaluated by computer-based visual function tests and subjective feedback. Main results The electrode impedance of both Argus I and II slowly decreased overtime after implantation, accompanied by a gradual increase in the perceptual threshold. A quantitative analysis of the impedance and retina-electrode distance revealed somewhat different causes of impedance change in Argus I vs. II. Evaluation of the visual functions restored and feedback from the subject suggest that the Argus II device enables improved spatial visual ability over Argus I, but adaptation to prosthetic vision did not lead to a measurable performance improvement in the standard visual function tests. Significance This study of Argus I and II in the same subject directly compares for the first time the interface properties and prosthetic vision in two eyes that share the same disease mechanism and converged visual pathway in higher visual centers, offering exciting new insights into the influence of the electrode parameters and layout to prosthetic vision. Trial registration Data collected within clinical trials registered at NIH (NCT00279500 & NCT01860092).

A wireless photovoltaic retinal prosthesis is currently being studied with the aim of providing prosthetic vision to patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). The major challenge of a photovoltaic device is its limited power efficiency. Our retinal prosthetic design implements a unique divisional power supply scheme (DPSS) system that provides the electrical power generated by all of the solar cells to only a subset of electrodes at any moment in time. The aim of the present study was to systematically characterize the spatiotemporal integration performance of the system under various DPSS conditions using human subjects and a psychophysical approach. A 16x16 pixels LED array controlled by Arduino was used to simulate the output signal of the DPSS design, and human performance under different visual stimulations at various update frequencies was then used to assess the spatiotemporal capability of retinal prostheses. The results showed that the contrast polarity of the image, image brightness, and division number influenced the lower limit of the update frequency of the DPSS system, while, on the other hand, visual angle, ambient light level, and stimulation order did not affect performance significantly. Pattern recognition by visual persistence with spatiotemporal integration of multiple frames of sparse dots is a feasible approach in retinal prosthesis design. These findings provide an insight into how to optimize a photovoltaic retinal prosthesis using a DPSS design with an appropriate update frequency for reliable pattern recognition. This will help the development of a wireless device able to restore vision to RP and AMD patients in the future.

Geometries of visual and kinesthetic spaces were estimated by alley experiments. For the visual alley, 24 observers set rods that extended in depth so that they appeared 1) to neither diverge nor converge, 2) to be separated by the same lateral distance, or 3) to be perpendicular to the frontal plane. The separation of rods and the height of the observer’s eyes were varied. Under each instruction, another group of 20 observers set the rods visually at eye level or kinesthetically without seeing the rods. We obtained these findings. First, the rods seen obliquely from above were set more accurately than the rods seen at eye level. Second, the visual settings were parallel to one another for small separation and were convergent to the observer for large separation, whereas the kinesthetic settings were divergent to the observer for the small separation and were convergent to the observer for the large separation. These differences between sense modalities were explained by the location of the egocenter(s) and the sensitivity to direction. Third, the visual or kinesthetic settings did not differ with instructions, suggesting that visual and kinesthetic spaces were Euclidean. Fourth, the visual angle of the near ends of the rods, plotted against that of the far ends, was described by Euclidean geometry, provided that the visual angle is exaggerated. Last, the kinesthetic angle of the near ends of the rods, plotted against that of the far ends, was not described by any simple geometry even when we assumed that the kinesthetic angle is exaggerated.

SynopsisA diversity of animals survive encounters with predators by escaping from a looming visual stimulus. Despite the importance of this behavior, it is generally unclear how visual cues facilitate a prey’s survival from predation. Therefore, the aim of this study was to understand how the visual angle subtended on the eye of the prey by the predator affects the distance of adult zebrafish (Danio rerio) from predators. We performed experiments to measure the threshold visual angle and mathematically modeled the kinematics of predator and prey. We analyzed the responses to the artificial stimulus with a novel approach that calculated relationships between hypothetical values for a threshold-stimulus angle and the latency between stimulus and response. These relationships were verified against the kinematic responses of zebrafish to a live fish predator (Herichthys cyanoguttatus). The predictions of our model suggest that the measured threshold visual angle facilitates escape when the predator’s approach is slower than approximately twice the prey’s escape speed. These results demonstrate the capacity and limits to how the visual angle provides a prey with the means to escape a predator.

Modulation of a neuron’s responses by the stimuli presented outside of its classical receptive field is ubiquitous in the visual system. This “surround modulation” mechanism is believed to be critical for efficient processing and leads to many well-known perceptual effects. The details of surround modulation, however, are still not fully understood. One of the open questions is related to the differences in surround modulation mechanisms in different cortical areas, and their interactions. Here we study patterns of surround modulation in primary visual cortex (V1) and middle temporal complex (hMT+) utilizing a well-studied effect in motion perception, where human observers’ ability to discriminate the drift direction of a grating improves as its size gets bigger if the grating has a low contrast, and deteriorates if it has a high contrast. We first replicated the findings in the literature with a behavioral experiment using small and large (1.67 and 8.05 degrees of visual angle) drifting gratings with either low (2%) or high (99%) contrast presented at the periphery. Next, using functional MRI, we found that in V1 with increasing size cortical responses increased at both contrast levels. Whereas in hMT+ with increasing size cortical responses remained unchanged or decreased at high contrast, and increased at low contrast, reflecting the perceptual effect. We also show that the divisive normalization model successfully predicts these activity patterns, and establishes a link between the behavioral results and hMT+ ​activity. We conclude that surround modulation patterns in V1 and hMT+ ​are different, and that the size-contrast interaction in motion perception is likely to originate in hMT+.

Significance Accommodation/convergence mismatch induced by 3D displays can cause discomfort symptoms such as those induced by accommodation/convergence mismatch in clinical vergence testing. We found that the limits of clear and single vision during vergence tests are very different between 3D and clinical tests. Clinical vergences should not be used as substitutes for measures of vergences in 3D displays. Purpose The purposes of this study were to determine whether the limits of clear and single binocular vision derived from phoropter prism vergence tests match the limits measured in a 3D display and to determine whether vergence mode, smooth versus jump, affected those limits in the 3D display. Methods We tested the phoropter prism vergence limits of clear and single vision at 40 cm in 47 binocular young adults. In separate sessions, we tested, in a 3D display, the analogous 40-cm vergence limits for smooth vergence and jump vergence. The 3D fixation target was a Maltese cross whose visual angle changed congruently with target disparity. Results Our mean phoropter vergence blur and break values were similar to those reported in previous studies. The mean smooth divergence limit was less in the 3D display (9.8Δ) than in the phoropter (12.8Δ). Most smooth convergence limits were much larger in the 3D display than in the phoropter, reaching the 35Δ limit of the 3D display without blur or diplopia in 24 subjects. Mean jump vergence limits were significantly smaller than smooth vergence limits in the 3D display. Conclusions The limits of clear and single binocular vision derived from phoropter vergence tests were not a good approximation of the analogous limits in our 3D display.

Various studies suggest the importance of peripheral vision (PV) in sports. Computer-based test systems provide objective methods to measure PV. Nevertheless, the reliability and training effects are not clarified in detail. The purpose of this investigation was to present a short narrative non-systematic review on computer-based PV tests and to determine the reliability and the training effects of peripheral perception sub-test (PP) of the Vienna test system (VTS) in a test&ndash, retest design. N = 21 male athletes aged between 20 and 30 years (M = 26.15, SD = 3.1) were included. The main outcome parameters were peripheral reaction (PR), PR left (PRL), PR right (PRR), field of vision (FOV), visual angle left (VAL), and visual angle right (VAR). Reliability was assessed using intraclass correlation coefficient (ICC) and Bland&ndash, Altman plots. Training effects were determined by students t-test. Good reliability was observed in PR, PRL, and PRR. Moderate reliability was found in FOV, VAL, and VAR. Significant improvements between T0 and T1 were found in PRL with a mean difference of 0.04 s (95% CI [0.00&ndash, 0.07]) and in PR with a mean difference of 0.02 s (95% CI [0.00&ndash, 0.05]). For PRR, FOV, VAL, VAR, no significant differences were detected. These results indicate that PP can be applied to asses PV abilities in sports. Future research is needed to clarify the influence of test repetitions on visuomotor learning in PP. Moreover, PV tests should be cross-validated with sport-specific measurements (e.g., on-field and/or &lsquo, virtual reality&rsquo, approaches).

Electrically stimulating early visual cortex results in a visual percept known as a phosphene. Although phosphenes can be evoked by a wide range of electrode sizes and current amplitudes, they are invariably described as small. To better understand this observation, we electrically stimulated 93 electrodes implanted in the visual cortex of 13 human subjects who reported phosphene size while stimulation current was varied. Phosphene size increased as the stimulation current was initially raised above threshold, but then rapidly reached saturation. Phosphene size also depended on the location of the stimulated site, with size increasing with distance from the foveal representation. We developed a model relating phosphene size to the amount of activated cortex and its location within the retinotopic map. First, a sigmoidal curve was used to predict the amount of activated cortex at a given current. Second, the amount of active cortex was converted to degrees of visual angle by multiplying by the inverse cortical magnification factor for that retinotopic location. This simple model accurately predicted phosphene size for a broad range of stimulation currents and cortical locations. The unexpected saturation in phosphene sizes suggests that the functional architecture of cerebral cortex may impose fundamental restrictions on the spread of artificially evoked activity and this may be an important consideration in the design of cortical prosthetic devices.SIGNIFICANCE STATEMENT Understanding the neural basis for phosphenes, the visual percepts created by electrical stimulation of visual cortex, is fundamental to the development of a visual cortical prosthetic. Our experiments in human subjects implanted with electrodes over visual cortex show that it is the activity of a large population of cells spread out across several millimeters of tissue that supports the perception of a phosphene. In addition, we describe an important feature of the production of phosphenes by electrical stimulation: phosphene size saturates at a relatively low current level. This finding implies that, with current methods, visual prosthetics will have a limited dynamic range available to control the production of spatial forms and that more advanced stimulation methods may be required.

In most organisms, specific structures are responsible for detecting light patterns and vision. Several species of sea urchins appear to have a diffuse photoreceptor system that enables them to detect light and in some cases objects. The presence of extraocular vision was investigated on a sea urchin common in northern Oman, Diadema setosum. Urchins from 8- to 10-m deep coral communities were used in controlled experiments that quantified the orientation response of the urchins to various visual cues: size, contrast and colour of circular targets simulating urchins’ outlines. Urchins responded to black discs down to 11° initial visual angle but not to smaller discs. The minimum grey-scale value triggering a response was between 50 and 37% black. Urchins responded to red targets but not to green or blue ones. An average angular distance between spines of 5.3° suggested a visual acuity of about 10.6°. D. setosum thus showed extraocular vision allowing them to detect objects of different sizes, contr...

Although the feasibility of brain-computer interface (BCI) systems based on steady-state visual evoked potential (SSVEP) has been extensively investigated, only a few studies have evaluated its clinical feasibility in patients with locked-in syndrome (LIS), who are the main targets of BCI technology. The main objective of this case report was to share our experiences of SSVEP-based BCI experiments involving five patients with LIS, thereby providing researchers with useful information that can potentially help them to design BCI experiments for patients with LIS. In our experiments, a four-class online SSVEP-based BCI system was implemented and applied to four of five patients repeatedly on multiple days to investigate its test-retest reliability. In the last experiments with two of the four patients, the practical usability of our BCI system was tested using a questionnaire survey. All five patients showed clear and distinct SSVEP responses at all four fundamental stimulation frequencies (6, 6.66, 7.5, 10 Hz), and responses at harmonic frequencies were also observed in three patients. Mean classification accuracy was 76.99% (chance level = 25%). The test-retest reliability experiments demonstrated stable performance of our BCI system over different days even when the initial experimental settings (e.g., electrode configuration, fixation time, visual angle) used in the first experiment were used without significant modifications. Our results suggest that SSVEP-based BCI paradigms might be successfully used to implement clinically feasible BCI systems for severely paralyzed patients.

Motion vision is important in guiding animal behavior. Both the retina and the visual cortex process object motion in largely unbiased fashion: all directions are represented at all locations in the visual field. We investigate motion processing in the superior colliculus of the awake mouse, by optically recording neural responses across both hemispheres. Within the retinotopic map, one finds large regions of ∼500 μm size where neurons prefer the same direction of motion. This preference is maintained in depth to ∼350 μm. The scale of these patches, ∼30 deg of visual angle, is much coarser than the animal’s visual resolution. A global map of motion direction shows approximate symmetry between the left and right hemispheres and a net bias for upward-nasal motion in the upper visual field. Unlike other parts of the early visual system, the superior colliculus develops a locally biased representation of object motion.

We provide the first measures of foveal cone density as a function of axial length in living eyes and discuss the physical and visual implications of our findings. We used a new generation Adaptive Optics Scanning Laser Ophthalmoscope to image cones at and near the fovea in 28 eyes of 16 subjects. Cone density and other metrics were computed in units of visual angle and linear retinal units. The foveal cone mosaic in longer eyes is expanded at the fovea, but not in proportion to eye length. Despite retinal stretching (decrease in cones/mm2), myopes generally have a higher angular sampling density (increase in cones/deg2) in and around the fovea compared to emmetropes, offering the potential for better visual acuity. Reports of deficits in best-corrected foveal vision in myopes compared to emmetropes cannot be explained by increased spacing between photoreceptors caused by retinal stretching during myopic progression., eLife digest The human eye has many different parts that enable sight. The retina is the light sensitive tissue at the back of the eye, and it contains the fovea, the region that provides the clearest vision. Light must be focused on the retina to create images, a feat achieved by the transparent parts at the front of the eye called the cornea and lens. These parts of the eye are called the optics. Between birth and adulthood, significant changes take place in the eye. Most noticeably, the distance between the optics and the fovea grows by about seven millimeters. Cells called cone photoreceptors, which provide light sensitivity, migrate and pack into the fovea. Finally, the eye’s optics adjust to maintain a sharp focus. At the same time, the brain is learning how to process inputs from the eyes to generate mental images that realistically correspond to the physical world around it. The development of the eye is fascinating in its complexity, but for more and more people, the process does not go as expected. Specifically, a growing proportion of the population has eyes that are too long. This means that, for light reflected by far away objects, the eye’s optics form an image in front of the retina instead of on it. As a result, images of distant objects cannot be seen clearly, a condition known as myopia or nearsightedness. Researchers have also discovered that nearsighted people see less clearly than those who do not use glasses, even when given a sharp image to examine at close range. It has been hypothesized that these deficits result from stretching of the retina as the eye becomes bigger. Until recently, testing this hypothesis by looking at cone photoreceptors directly in the eye was impossible. This is because the optics of all eyes have small imperfections that distort the light passing through them, including any light used to take high resolution microscopic images of the fovea. This hurdle can be overcome using adaptive optics, which means adding a deformable mirror to the instrument being used to image the eye that can adjust to correct the distortion. Wang et al. use a new generation Adaptive Optics Scanning Laser Ophthalmoscope to check the density of cones at the fovea in relation to the size of the eye. They show that although the center of the fovea has fewer cones when the eye is bigger, this effect is more than offset because the longer eye increases magnification. So, if a near-sighted person wearing contacts and someone who does not need glasses stood side-by-side admiring the full moon, the near-sighted person would most likely have more cones sampling the image and should therefore have a higher resolution view. These findings rule out reductions in the density of cone photoreceptors as the cause or effect of visual deficits associated with near-sightedness, adding to the understanding of this common condition.

About 30-40% of stroke patients suffer from visual field defects following injury. These can interfere with the standard neuropsychological assessment and complicate the interpretation of tests that use visual materials. However, information about the integrity of a patient's central visual field is often unavailable. We, therefore, designed a screening tool, the computerized visual field test (c-VFT), specifically targeted at providing easily available, but rough, information about patients' central visual field. c-VFT was tested in two samples of stroke patients. Eleven patients were tested on c-VFT and on the Esterman test. Five patients were tested on c-VFT and the Humphrey Visual Field Analyzer (HFA), central 10-2. Criterion validity of the c-VFT was investigated by calculating quadrantwise intraclass correlation for both comparisons. For the HFA comparison, we also calculated point-to-point intraclass correlation, sensitivity, and specificity. Analyses revealed moderately good correspondence between c-VFT and the Esterman test, and between c-VFT and HFA 10-2, respectively. When looking specifically at test points within one degree of visual angle apart in the two tests, intraclass correlation increased. For these points, the sensitivity of c-VFT was 0.89 and specificity was 0.97. While the c-VFT is not designed to be diagnostic nor to replace the detailed visual field analysis, this study shows that it provides a reasonable screening of the central visual field. The test can easily be used and will be made freely available to neuropsychological clinicians and researchers.The open access test can be found here: https://tinyurl.com/ysz9b28c

Simulated images were generated using an extended source to illustrate peripheral dark shadows in pseudophakic eye models. The shadows are a consequence of the intraocular lens being much smaller than the natural crystalline lens, which limits the extent of the focused image. Compensation is made for the cosine intensity falloff due to pupil obliquity, and the images are envisaged as being displayed on polar plots of visual angle corresponding to approximate retinal locations. Additional retinal illumination from light missing the lens reduces the shadow effect as the pupil diameter increases, in agreement with clinical observations. Lenses with two different cross-sectional profiles were evaluated, which both have shadows at about 85°, but with different characteristics. The iris thickness was found to affect the shadows by occluding peripheral rays. Images were also generated for a point source with a 5 mm pupil, where a double image is created for visual angles as low as 50°, which may contribute to visual phenomena at night. This type of modeling may help with patient evaluations and discussions.

Background: The ability to read is an important factor in the quality of life. Choroideremia is an inherited retinal degeneration presenting with gradual, progressive constriction of the central visual field, providing a useful disease model to investigate the impact of the visual field on reading ability.Objective: The aim of this study was to provide practical guidance on the usefulness of measuring reading ability in patients.Method: The Radner Reading Test was administered to 33 patients (65 eyes with choroideremia). To quantify the residual retinal area, the patients underwent microperimetry and imaging. The visual angle subtended by the largest letter read by each subject was calculated using Emsley’s Model Eye.Results: A minimum of 1 letter must be seen to allow the eye to read, with preservation of foveal sensitivity. The relationship between reading speed and acuity varies with the visual field. The reading speed is higher in eyes with an intact fovea (p < 0.001 right eye, p = 0.06 left eye). Qualitative analysis of the direction of the intact retina did not indicate any directional impact on measurements.Conclusions: In order to read, an eye must have enough retinal width close to the fovea to see at least 1 full letter. Direction of print does not impact the ability to read, allowing results from different languages to be combined in clinical trials.

Purpose Crowding refers to the phenomenon in which objects that can be recognized when viewed in isolation are unrecognizable in clutter. Crowding sets a fundamental limit to the capabilities of the peripheral vision and is essential in explaining performance in a broad array of daily tasks. Due to the effects of glaucoma on peripheral vision, we hypothesized that neural loss in the disease would lead to stronger effects of visual crowding. Methods Subjects were asked to discriminate the orientation of a target letter when presented with surrounding flankers. The critical spacing value (scritical), which was required for correct discrimination of letter orientation, was obtained for each quadrant of the visual field. scritical values were correlated with standard automated perimetry (SAP) mean sensitivity (MS) and optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements. Results The study involved 13 subjects with mild glaucomatous visual field loss and 13 healthy controls. Glaucomatous eyes had significantly greater (worse) scritical than controls (170.4 ± 27.1 vs. 145.8 ± 28.0 minimum of visual angle, respectively; P = 0.007). scritical measurements were significantly associated with RNFL thickness measurements (R2 = 26%; P < 0.001) but not with SAP MS (P = 0.947). Conclusions In glaucoma patients, a pronounced visual crowding effect is observed, even in the presence of mild visual field loss on standard perimetry. scritical was associated with the amount of neural loss quantified by OCT. These results may have implications for understanding how glaucoma patients are affected in daily tasks where crowding effects may be significant.

The accommodation is a reflex action of the eye, in response to focusing on a near target, then looking at a distance target (and vice versa), comprising coordinated changes in vergence, crystal lens shape and pupil size. Convergence is a vergence adduction movement that increase the visual angle to permit single binocular vision during near viewing. Convergence can be voluntary but need not be no near stimulus need be present to elicit vergence. It is also reflexive and a co-movement in the near response.

Our aim is to develop a new generation of suprachoroidal–transretinal stimulation (STS) retinal prosthesis using a dual-stimulating electrode array to enlarge the visual field. In the present study, we aimed to examine how position and size of the visual field—created by a retinal prosthesis simulator—influenced mobility. Twelve healthy subjects wore retinal prosthesis simulators. Images captured by a web camera attached to a head-mounted display (HMD) were processed by a computer and displayed on the HMD. Three types of artificial visual fields—designed to imitate phosphenes—obtained by a single (5 × 5 electrodes; visual angle, 15°) or dual (5 × 5 electrodes ×2; visual angle, 30°) electrode array were created. Visual field (VF)1 is an inferior visual field, which corresponds to a dual-electrode array implanted in the superior hemisphere. VF2 is a superior visual field, which corresponds to a single-electrode array implanted in the inferior hemisphere. VF3 is a superior visual field, which corresponds to a dual-electrode array implanted in the inferior hemisphere. In each type of artificial visual field, a natural circular visual field (visual angle, 5°) which imitated the vision of patients with advanced retinitis pigmentosa existed at the center. Subjects were instructed to walk along a black carpet (6 m long × 2.2 m wide) without stepping on attached white circular obstacles. Each obstacle was 20 cm in diameter, and obstacles were installed at 40-cm intervals. We measured the number of footsteps on the obstacles, the time taken to complete the obstacle course, and the extent of head movement to scan the area (head-scanning). We then compared the results recorded from these 3 types of artificial visual field. The number of footsteps on obstacles was lowest in VF3 (One-way ANOVA; P = 0.028, Fisher’s LSD; VF 1 versus 3 P = 0.039, 2 versus 3 P = 0.012). No significant difference was observed for the time to complete the obstacle course or the extent of head movement between the 3 visual fields. The superior and wide visual field (VF3) obtained by the retinal prosthesis simulator resulted in better mobility performance than the other visual fields.

Purpose To use ray-tracing analysis and simulated retinal illumination profiles to design an intraocular lens (IOL) that prevents or reduces negative dysphotopsia after cataract surgery. Setting Mayo Clinic, Rochester, Minnesota, and Simpson Optics LLC, Arlington, Texas, USA. Design Experimental study. Methods Ray-tracing software was used to simulate peripheral retina illumination from an extended light source for a pseudophakic eye with a biconvex high refractive index IOL. Ray intensities were adjusted to include the effects of the surface reflections and the energy reduction caused by pupil obliquity at high incident angles. The results were compared with similar optical modeling of a modified IOL design with a concave region on the peripheral posterior surface. Results For a standard biconvex high refractive index IOL, simulated retina illumination profiles showed an area of nonilluminated peripheral nasal retina at a relative visual angle of approximately 85 degrees to 93 degrees. Using a modified IOL optic with a peripheral concave posterior surface, ray-tracing diagrams showed that peripheral input rays were redirected anteriorly into the nonilluminated dark area of the peripheral retina. Simulated retina illumination images confirmed that the redirected input rays improved illumination to the peripheral retina, including the dark area. Conclusions Optical modeling showed that the new IOL design provides more uniform illumination of the peripheral nasal retina and specifically illuminates the dark region of the nasal retina associated with negative dysphotopsia. This modified IOL design could prevent or reduce negative dysphotopsia after cataract surgery.

This study examined the dynamic coordination between disconjugate, vergence eye movements, and pupil size in 52 normal subjects during binocular disparity stimulation in a virtual reality display. Eye movements and pupil area were sampled with a video-oculographic system at 100 Hz during performance of two tasks, (1) fusion of a binocular disparity step (±1.5° of visual angle in the horizontal plane) and (2) pursuit of a sinusoidally varying binocular disparity stimulus (0.1 Hz, ±2.6° of visual angle in the horizontal plane). Pupil size data were normalized on the basis of responses to homogeneous illumination increments ranging from 0.42 to 65.4 cd/m2. The subjects produced robust vergence eye movements in response to disparity step shifts and high fidelity sinusoidal vergence responses (R2 relative to stimulus profile: 0.933 ± 0.088), accompanied by changes in pupil area. Trajectory plots of pupil area as a function of vergence angle showed that the pupil area at zero vergence is altered between epochs of linear vergence angle—pupil area relations. Analysis with a modified Gath-Geva clustering algorithm revealed that the dynamic relationship between the ocular vergence angle and pupil size includes two different transient, synkinetic response patterns. The near response pattern, pupil constriction during convergence and pupil dilation during divergence, occurred ~80% of the time across subjects. An opposite, previously undescribed synkinetic pattern was pupil constriction during divergence and pupil dilatation during convergence; it occurred ~15% of the time across subjects. The remainder of the data were epochs of uncorrelated activity. The pupil size intercepts of the synkinetic segments, representing pupil size at initial tropia, had different relationships to vergence angle for the two main coordinated movement types. Hippus-like movements of the pupil could also be accompanied by vergence movements. No pupil coordination was observed during a conjugate pursuit task. In terms of the current dual interaction control model (1), findings suggest that the synkinetic eye and pupillary movements are produced by a dynamic switch of the influence of vergence related information to pupil control, accompanied by a resetting of the pupil aperture size at zero-vergence.

Purpose The dorsal attention network (DAN) and the ventral attention network (VAN) are known to support visual attention, but the influences of ocular dominance on the attention networks are unclear. We aimed to explore how visual cortical asymmetry of the attention networks correlate with neurophysiological oscillation and connectivity markers of attentional processes. Methods An oddball task with concentric circle stimuli of three different sizes (i.e., spot size of 5°, 20°, or 30° of visual angle) was used to vary task difficulty. Event-related oscillations and interareal communication were tested with an electroencephalogram-based visual evoked components as a function of ocular dominance in 30 healthy subjects. Results Accuracy rates were higher in the dominant eyes compared with the nondominant eyes. Compared with the nondominant eyes, the dominant eyes had higher theta, low-alpha, and low-beta powers and lower high-alpha powers within the nodes of VAN and DAN. Furthermore, visual information processed by the dominant and nondominant eye had different fates, that is, the dominant eyes mainly relied on theta and low-alpha connectivity within both the VAN and the DAN, whereas the nondominant eyes mainly relied on theta connectivity within the VAN and high-alpha connectivity within the DAN. The difference in accuracy rate between the two eyes was correlated with the low-alpha oscillations in the anterior DAN area and low-alpha connectivity of the left DAN. Conclusions The ocular dominance processing and interareal communication reveal a cortical asymmetry underlying attention, and this reflects a two-way modulatory mechanism within attention networks in the human brain.

We present toBeeView, a program that produces from a digital photograph, or a set of photographs, an approximation of the image formed at the sampling station stage in the eye of an animal. toBeeView is freely available from https://github.com/EEZA-CSIC/compound-eye-simulator. toBeeView assumes that sampling stations in the retina are distributed on a hexagonal grid. Each sampling station computes the weighted average of the color of the part of the visual scene projecting on its photoreceptors, and the hexagon of the output image associated with the sampling station is filled in this average color. Users can specify the visual angle subtended by the scene and the basic parameters determining the spatial resolution of the eye: photoreceptor spatial distribution and optic quality of the eye. The photoreceptor distribution is characterized by the vertical and horizontal interommatidial angles—which can vary along the retina. The optic quality depends on the section of the visual scene projecting onto each sampling station, determined by the acceptance angle. The output of toBeeView provides a first approximation to the amount of visual information available at the retina for subsequent processing, summarizing in an intuitive way the interaction between eye optics and receptor density. This tool can be used whenever it is important to determine the visual acuity of a species and will be particularly useful to study processes where object detection and identification is important, such as visual displays, camouflage, and mimicry.

Visual discomfort is predicted from a luminance map with a model based on the receptive field mechanism in the human eye. A centre-surround receptive field is described by a Difference of Gaussians. Eight commercially available office luminaires are assessed for visual discomfort in a paired comparison experiment. The correlation between the subjective data and the receptive field model is optimized for three factors: the centre Gaussian width, the surround Gaussian width and the centre-to-surround weighing factor (WF). A centre and surround visual angle of 0.53 and 2.19 min arc, respectively, and a WF of 0.87 result in a coefficient of determination of 0.77. The model is validated independently with magnitude estimation data obtaining a coefficient of determination of 0.82. Where the standard unified glare rating method fails (coefficient of determination of 0.45), the receptive field model ameliorates predictability for visual discomfort. The model based on receptive fields is promising to replace current standard glare metrics, specifically when non-uniform luminaires are to be evaluated.

The current study aims to create some general guidance for designers to better understand the impact of background lighting in their design and as a result minimize its effect on the visual saliency of urban objects. There are few studies about how lighting clutters can affect and decrease the visual saliency of illuminated urban objects at night. Lack of information in this area has resulted in increasing luminance to be recognized as one of the main tools to enhance the saliency of urban objects at night. To address this matter a study was performed to investigate the effect of proximity of lighting clutters on visual saliency of urban objects. A forced choice pair comparison method was employed, in which two test images of an urban object in different conditions of luminance contrast and proximity of light patterns were compared. Test participants reported in which image the target appeared more salient. Results show there is a progressive increase in saliency value by increasing the gap between the target and the background lighting when the luminance contrast of the target is three or higher. However, the critical area around the object with the highest effect lies between 0.5° and 1° visual angle. Removing light patterns beyond that point creates negligible effect. The findings of this study could inform development of future models of visual recognition in the road environment, models which can address the important effects of environmental context in addition to photometric variables (luminance and contrast) that are the only factors considered in traditional models of ‘Visibility Level.’

Video-based eye tracking relies on locating pupil center to measure gaze positions. Although widely used, the technique is known to generate spurious gaze position shifts up to several degrees in visual angle because pupil centration can change without eye movement during pupil constriction or dilation. Since pupil size can fluctuate markedly from moment to moment, reflecting arousal state and cognitive processing during human behavioral and neuroimaging experiments, the pupil size artifact is prevalent and thus weakens the quality of the video-based eye tracking measurements reliant on small fixational eye movements. Moreover, the artifact may lead to erroneous conclusions if the spurious signal is taken as an actual eye movement. Here, we measured pupil size and gaze position from 23 human observers performing a fixation task and examined the relationship between these two measures. Results disclosed that the pupils contracted as fixation was prolonged, at both small (

The spontaneity and ease with which we point understates the gesture’s significance to understanding cognition. Onset of pointing in infancy predicts early word acquisition and signals a capacity for shared intentionality. Yet, notwithstanding its importance, there is little research on the perception of pointing and its referents. Here we show that perceptual acuity for discerning where another person is pointing is remarkably accurate. Thresholds, as low as 0.5° of visual angle across an interpersonal distance of ∼2 m, are modulated by the referent’s location in space and the hand used to point and remain constant when the pointer’s eyes are occluded from view and when ‘embodiment’ cues are enhanced or minimized. Pointing with the index finger not only directs attention toward a general region of space but the morphology of arm, hand and finger can be used to discern the location of the pointer’s attention with precision.

The study was a previous research for spatial distribution characteristics of the spectral luminous efficiency function in the whole field of vision. Psychophysical experiments were conducted to investigate the spatial distribution of brightness perception and the optimal experimental sampling parameters by direct brightness-matching method. Two visual stimuli, a central fixation point and a peripheral target, were presented in different combinations of shape, color, luminance, diameterandspatial position, to explore the sensitivity of human eyes. The compared target was gradually moved away from the position adjacent to the fixation point. After moving of every sampling step, subjects responded whether the brightness of two stimuli were the same. Statistical analyses showed theconclusions as follows. (1) Blue was the most sensitive color to eyes, under the condition that diameters and directions of the stimuli were the same. (2) Under the condition that colors and directions were the same, the smaller diameter caused the more sensitive perception. (3) The visual perception of the human eye had spacialdistribution characteristics: the left visualfield was more sensitive than the superior field; the inferior field was more sensitive than the superior field; and under partially parametricalconditionsthe left field was more sensitive than the inferior field. These discrepancies of the brightness sensitivity in space domain could be explained by the heterogeneous photoreceptor distribution. Finally, we obtainedthe optimal combination ofparametrical levels ofstimuli for the spatial sampling of the brightness perception: blue color, diameter of 0.5° visual angle.

Animals use vision over a wide range of light intensities, from dim starlight to bright sunshine. For animals active in very dim light the visual system is challenged by several sources of visual noise. Adaptations in the eyes, as well as in the neural circuitry, have evolved to suppress the noise and enhance the visual signal, thereby improving vision in dim light. Among neural adaptations, spatial summation of visual signals from neighboring processing units is suggested to increase the reliability of signal detection and thus visual sensitivity. In insects, the likely neural candidates for carrying out spatial summation are the lamina monopolar cells (LMCs) of the first visual processing area of the insect brain (the lamina). We have classified LMCs in three species of hawkmoths with considerably different activity periods but very similar ecology-the diurnal Macroglossum stellatarum, the nocturnal Deilephila elpenor and the crepuscular-nocturnal Manduca sexta. Using this classification, we investigated the anatomical adaptations of hawkmoth LMCs suited for spatial summation. We found that specific types of LMCs have dendrites extending to significantly more neighboring cartridges in the two nocturnal and crepuscular species than in the diurnal species, making these LMC types strong candidates for spatial summation. Moreover, while the absolute number of cartridges visited by the LMCs differed between the two dim-light species, their dendritic extents were very similar in terms of visual angle, possibly indicating a limiting spatial acuity. The overall size of the lamina neuropil did not correlate with the size of its LMCs.