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Purpose: The long-term, low-resolution vision experienced by individuals affected by retinal disease that causes central vision loss (CVL) may change their perception of blur through adaptation. This study used a short-term adaptation paradigm to evaluate adaptation to blur and sharpness in patients with CVL., Methods: A variation of Webster's procedure was used to measure the point of subjective neutrality (PSN). The image that appeared normal after adaptation to each of seven blur and sharpness levels (PSN) was measured in 12 patients with CVL (20/60 to 20/320) and 5 subjects with normal sight (NS). Patients with CVL used a preferred retinal locus to view the images. Small control studies investigated the effects of long-term and medium-term (1 hour) defocus and diffusive blur., Results: Adaptation was reliably measured in patients with CVL and in the peripheral vision of NS subjects. The shape of adaptation curves was similar in patients with CVL and both central and peripheral vision of NS subjects. No statistical correlations were found between adaptation and age, visual acuity, retinal eccentricity, or contrast sensitivity. Long-term blur experience by a non-CVL myopic participant caused a shift in the adaptation function. Conversely, medium-term adaptation did not cause a shift in the adaptation function., Conclusions: Blur and sharp short-term adaptation occurred in peripheral vision of normal and diseased retinas. In most patients with CVL, neither adaptation nor blur perception was affected by long-term attention to peripheral low-resolution vision. The impact of blur/sharp adaptation on the benefit of image enhancement techniques for patients with CVL is discussed.

Background: Visual impairment associated with central field loss may make vehicle control more difficult due to the degraded view of the road. We evaluated how central field loss affects vehicle control in a driving simulator., Methods: Nineteen participants with binocular central field loss (acuity 6/9 to 6/60) and 15 controls with normal vision drove 10 scenarios, each about eight to 12 minutes. Speed, lane offset and steering wheel reversal rate were measured on straights, left and right curves, along city (approximately 50 km/h) and rural highway (approximately 100 km/h) routes. Following distance was measured on two city straight segments., Results: Subjects with central field loss had higher steering wheel reversal rates (0.55 versus 0.45 reversals per second, p = 0.015), suggesting that the steering task was more demanding for them, requiring more steering corrections; however, they did not differ in other performance measures. Nearly all maintained a safe following distance, although they were more likely than controls with normal vision to lose sight of the lead car in scenarios that required following a car., Conclusions: Most measures of vehicle control did not significantly differ between participants with central field loss and those with normal vision; however, the higher steering wheel reversal rates suggest that, in compensating for their vision impairment, drivers with central field loss had to allocate extra steering effort to maintain their lane position, which in turn could reduce attentional resources for other driving tasks., (© 2016 Optometry Australia.)

The ability of the visual system to compensate for differences in blur orientation between eyes is not well understood. We measured the orientation of the internal blur code in both eyes of the same subject monocularly by presenting pairs of images blurred with real ocular point spread functions (PSFs) of similar blur magnitude but varying in orientations. Subjects assigned a level of confidence to their selection of the best perceived image in each pair. Using a classification-images-inspired paradigm and applying a reverse correlation technique, a classification map was obtained from the weighted averages of the PSFs, representing the internal blur code. Positive and negative neural PSFs were obtained from the classification map, representing the neural blur for best and worse perceived blur, respectively. The neural PSF was found to be highly correlated in both eyes, even for eyes with different ocular PSF orientations (rPos = 0.95; rNeg = 0.99; p < 0.001). We found that in subjects with similar and with different ocular PSF orientations between eyes, the orientation of the positive neural PSF was closer to the orientation of the ocular PSF of the eye with the better optical quality (average difference was ∼10°), while the orientation of the positive and negative neural PSFs tended to be orthogonal. These results suggest a single internal code for blur with orientation driven by the orientation of the optical blur of the eye with better optical quality.

Purpose: To measure natural image search performance in patients with central vision impairment. To evaluate the performance effect for a JPEG based image enhancement technique using the visual search task., Methods: One hundred and fifty JPEG images were presented on a touch screen monitor in either an enhanced or original version to 19 patients (visual acuity 0.4-1.2 logMAR, 6/15 to 6/90, 20/50 to 20/300) and seven normally sighted controls (visual acuity -0.12 to 0.1 logMAR, 6/4.5 to 6/7.5, 20/15 to 20/25). Each image fell into one of three categories: faces, indoors, and collections. The enhancement was realized by moderately boosting a mid-range spatial frequency band in the discrete cosine transform (DCT) coefficients of the image luminance component. Participants pointed to an object in a picture that matched a given target displayed at the upper-left corner of the monitor. Search performance was quantified by the percentage of correct responses, the median search time of correct responses, and an 'integrated performance' measure - the area under the curve of cumulative correct response rate over search time., Results: Patients were able to perform the search tasks but their performance was substantially worse than the controls. Search performances for the three image categories were significantly different (p <= 0.001) for all the participants, with searching for faces being the most difficult. When search time and correct response were analyzed separately, the effect of enhancement led to increase in one measure but decrease in another for many patients. Using the integrated performance, it was found that search performance declined with decrease in acuity (p = 0.005). An improvement with enhancement was found mainly for the patients whose acuity ranged from 0.4 to 0.8 logMAR (6/15 to 6/38, 20/50 to 20/125). Enhancement conferred a small but significant improvement in integrated performance for indoor and collection images (p = 0.025) in the patients., Conclusion: Search performance for natural images can be measured in patients with impaired vision to evaluate the effect of image enhancement. Patients with moderate vision loss might benefit from the moderate level of enhancement used here., (© 2012 The College of Optometrists.)

Visually impaired people may legally drive if wearing bioptic telescopes in some developed countries. To address the controversial safety issue of the practice, we have developed a low-cost in-car recording system that can be installed in study participants' own vehicles to record their daily driving activities. We also developed a set of automated identification techniques of informative behaviors to facilitate efficient manual review of important segments submerged in the vast amount of uncontrolled data. Here, we present the methods and quantitative results of the detection performance for six types of driving maneuvers and behaviors that are important for bioptic driving: bioptic telescope use, turns, curves, intersections, weaving, and rapid stops. The testing data were collected from one normally sighted and two visually impaired subjects across multiple days. The detection rates ranged from 82% up to 100%, and the false discovery rates ranged from 0% to 13%. In addition, two human observers were able to interpret about 80% of targets viewed through the telescope. These results indicate that with appropriate data processing the low-cost system is able to provide reliable data for natural bioptic driving studies.

We have developed a range of vision rehabilitation devices and techniques for people with impaired vision due to either central vision loss or severely restricted peripheral visual field. We have conducted evaluation studies with patients to test the utilities of these techniques in an effort to document their advantages as well as their limitations. Here we describe our work on a visual field expander based on a head mounted display (HMD) for tunnel vision, a vision enhancement device for central vision loss, and a frequency domain JPEG/MPEG based image enhancement technique. All the evaluation studies included visual search paradigms that are suitable for conducting indoor controllable experiments.

Severe visual field constriction (tunnel vision) impairs the ability to navigate and walk safely. We evaluated Trifield glasses as a mobility rehabilitation device for tunnel vision in an extended wearing trial. Twelve patients with tunnel vision (5-22 degrees wide) due to retinitis pigmentosa or choroideremia participated in the 5-visit wearing trial. To expand the horizontal visual field, one spectacle lens was fitted with two apex-to-apex prisms that vertically bisected the pupil on primary gaze. This provides visual field expansion at the expense of visual confusion (two objects with the same visual direction). Patients were asked to wear these spectacles as much as possible for the duration of the wearing trial (median 8, range 6-60 weeks). Clinical success (continued wear, indicating perceived overall benefit), visual field expansion, perceived direction and perceived visual ability were measured. Of 12 patients, nine chose to continue wearing the Trifield glasses at the end of the wearing trial. Of those nine patients, at long-term follow-up (35-78 weeks), three reported still wearing the Trifield glasses. Visual field expansion (median 18, range 9-38 degrees) was demonstrated for all patients. No patient demonstrated adaptation to the change in visual direction produced by the Trifield glasses (prisms). For reported difficulty with obstacles, some differences between successful and non-successful wearers were found. Trifield glasses provided reported benefits in obstacle avoidance to 7 of the 12 patients completing the wearing trial. Crowded environments were particularly difficult for most wearers. Possible reasons for long-term discontinuation and lack of adaptation to perceived direction are discussed.

Purpose: A device was developed to provide an expanded visual field to patients with tunnel vision by superimposing minified edge images of the wide scene, in which objects appear closer to the heading direction than they really are. Experiments were conducted in a virtual environment to determine whether users would overestimate collision risks., Methods: Given simulated scenes of walking or standing with intention to walk toward a given direction (intended walking) in a shopping mall corridor, participants (12 normally sighted and 7 with tunnel vision) reported whether they would collide with obstacles appearing at different offsets from variable walking paths (or intended directions), with and without the device. The collision envelope (CE), a personal space based on perceived collision judgments, and judgment uncertainty (variability of response) were measured. When the device was used, combinations of two image scales (5x minified and 1:1) and two image types (grayscale or edge images) were tested., Results: Image type did not significantly alter collision judgment (P > 0.7). Compared to the without-device baseline, minification did not significantly change the CE of normally sighted subjects for simulated walking (P = 0.12), but increased CE by 30% for intended walking (P < 0.001). Their uncertainty was not affected by minification (P > 0.25). For the patients, neither CE nor uncertainty was affected by minification (P > 0.13) in both walking conditions. Baseline CE and uncertainty were greater for patients than normally sighted subjects in simulated walking (P = 0.03), but the two groups were not significantly different in all other conditions., Conclusions: Users did not substantially overestimate collision risk, as the x5 minified images had only limited impact on collision judgments either during walking or before starting to walk.

Both visually salient and top-down information are important in eye movement control, but their relative roles in the planning of daily saccades are unclear. We investigated the effect of peripheral vision loss on saccadic behaviors in patients with tunnel vision (visual field diameters 7 degrees-16 degrees) in visual search and real-world walking experiments. The patients made up to two saccades per second to their pre-saccadic blind areas, about half of which had no overlap between the post- and pre-saccadic views. In the visual search experiment, visual field size and the background (blank or picture) did not affect the saccade sizes and direction of patients (n = 9). In the walking experiment, the patients (n = 5) and normal controls (n = 3) had similar distributions of saccade sizes and directions. These findings might provide a clue about the large extent of the top-down mechanism influence on eye movement control.

Purpose: To determine how severe peripheral field loss (PFL) affects the dispersion of eye movements relative to the head in patients walking in real environments. This information should help to define the visual field and clearance requirements for head-mounted mobility visual aids., Methods: Eye positions relative to the head were recorded in five patients with retinitis pigmentosa who had less than 15 degrees of visual field and in three normally sighted people, each walking in varied environments for more than 30 minutes. The eye-position recorder was made portable by modifying a head-mounted system (ISCAN, Burlington, MA). Custom data processing was implemented, to reject unreliable data. Sample standard deviations of eye position (dispersion) were compared across subject groups and environments., Results: The patients with PFL exhibited narrower horizontal eye-position dispersions than did the normally sighted subjects (9.4 degrees vs. 14.2 degrees , P < 0.0001), and the vertical dispersions of patients with PFL were smaller when they were walking indoors than when walking outdoors (8.2 degrees vs. 10.3 degrees ; P = 0.048)., Conclusions: When walking, the patients with PFL did not increase their scanning eye movements to compensate for missing peripheral vision information. Their horizontal scanning was actually reduced, possibly because of lack of peripheral stimulation. The results suggest that a field of view as wide as 40 degrees may be needed for closed (immersive) head-mounted mobility aids, whereas a much narrower display, perhaps as narrow as 20 degrees , may be sufficient with an open design.

Purpose: To study the effect of an augmented-vision device that superimposes minified contour images over natural vision on visual search performance of patients with tunnel vision., Methods: Twelve subjects with tunnel vision searched for targets presented outside their visual fields (VFs) on a blank background under three cue conditions (with contour cues provided by the device, with auditory cues, and without cues). Three subjects (VF, 8 degrees -11 degrees wide) carried out the search over a 90 degrees x 74 degrees area, and nine subjects (VF, 7 degrees -16 degrees wide) carried out the search over a 66 degrees x 52 degrees area. Eye and head movements were recorded for performance analyses that included directness of search path, search time, and gaze speed., Results: Directness of the search path was greatly and significantly improved when the contour or auditory cues were provided in the larger and the smaller area searches. When using the device, a significant reduction in search time (28% approximately 74%) was demonstrated by all three subjects in the larger area search and by subjects with VFs wider than 10 degrees in the smaller area search (average, 22%). Directness and gaze speed accounted for 90% of the variability of search time., Conclusions: Although performance improvement with the device for the larger search area was obvious, whether it was helpful for the smaller search area depended on VF and gaze speed. Because improvement in directness was demonstrated, increased gaze speed, which could result from further training and adaptation to the device, might enable patients with small VFs to benefit from the device for visual search tasks.

Subjects with central field loss (CFL) individually selected enhancement parameters to improve visibility of static video images. The effect of enhancement on performance and on perceived quality of motion video was assessed. Performance, e.g. recognition of visual details, was assessed by having subjects answer questions regarding visual information contained in the video motion segments that were enhanced using the individually-selected parameters. Enhancement did not improve subject performance on questions about video content. This result might be due to a ceiling effect limitation of the performance assessment method. In a second procedure, subjects' continuous perceptions of quality (using an adjective-based rating scale) were made while the enhancement parameters were abruptly switched among multiple values; these included the individually-selected enhancements, as well as unenhanced, over-enhanced, and degraded segments. The results indicate that adaptive enhancement (individually-tuned using a static image) adds significantly to perceived image quality when viewing motion video. Subjects who selected stronger contrast enhancement also perceived the enhancement to provide a larger benefit in image quality.

Purpose: We examined the relationship between visual field extent and driving performance in an open, on-road environment using a detailed scoring method that assessed the quality of specific skills for a range of maneuvers. The purpose was to determine which maneuvers and skills should be included in future, larger scale investigations of the effect of peripheral field loss on driving performance., Methods: Twenty-eight current drivers (67 +/- 14 years) with restricted peripheral visual fields participated. Binocular visual field extent was quantified using Goldmann perimetry (V4e target). The useful field of view (UFOV) and Pelli-Robson letter contrast sensitivity tests were administered. Driving performance was assessed along a 14-mile route on roads in the city of Birmingham, Alabama. The course included a representative variety of general driving maneuvers, as well as maneuvers expected to be difficult for people with restricted fields., Results: Drivers with more restricted horizontal and vertical binocular field extents showed significantly (p < or = 0.05) poorer skills in speed matching when changing lanes, in maintaining lane position and keeping to the path of the curve when driving around curves, and received significantly (p < or = 0.05) poorer ratings for anticipatory skills. Deficits in UFOV performance and poorer contrast sensitivity scores were significantly (p < or = 0.05) correlated with overall driving performance as well as specific maneuver/skill combinations., Conclusions: In a small sample of drivers, mild to moderate peripheral visual field restrictions were adversely associated with specific driving skills involved in maneuvers for which a wide field of vision is likely to be important (however most were regarded as safe drivers). Further studies using similar assessment methods with drivers with more restricted fields are necessary to determine the minimum field extent for safe driving.

Wideband enhancement was implemented by detecting visually relevant edge and bar features in an image to produce a bipolar contour map. The addition of these contours to the original image resulted in increased local contrast of these features and an increase in the spatial bandwidth of the image. Testing with static television images revealed that visually impaired patients (n = 35) could distinguish the enhanced images and preferred them over the original images (and degraded images). Most patients preferred a moderate level of wideband enhancement, since they preferred natural-looking images and rejected visible artifacts of the enhancement. Comparison of the enhanced images with the originals revealed that the improvement in the perceived image quality was significant for only 22% of the patients. Possible reasons for the limited increase in perceived image quality are discussed, and improvements are suggested.

Purpose: An augmented-view device for patients with severely restricted peripheral visual fields (tunnel vision) was proposed, combining a see-through head-mounted display and a simultaneous minified view of a wide field presented as contour information. Here we create and evaluate multiple implementations of the augmented-view concept and report responses from potential users., Methods: Several prototypes using commercial off-the-shelf devices were implemented. Then they were evaluated in real environments in daylight and at night by two retinitis pigmentosa patients., Results: Effective expansion of the visual field of patients was achieved. Patients indicated their preferences for different properties, devices, and combinations., Conclusions: Patients found the augmented-view concept of help for their impairment, but wanted much more ergonomic design than the prototypes provided. Benefits, limitations, and possible improvements for the evaluated devices are discussed.

Concerns about potentially harmful effects on the visual system due to the use of head mounted displays (HMDs) in general, and stereoscopic systems in particular, have been raised in the literature. Most of the concerns were based on studies measuring visual function changes following short-term use of HMDs. This study measured functional changes in binocular vision, accommodation, and resolution following 30 min use of HMD in both stereoscopic- and non-stereoscopic modes, and compared them to changes following the same task performed on a desk-top CRT display. No functional differences were found between HMD and CRT and most measured changes were too small to be considered clinically meaningful. An evaluation of subjective comfort found a statistically significant difference in the impression of comfort between the CRT and the HMD in stereoscopic mode, with the latter being less comfortable. It can be concluded that the functional changes reported following short term use of HMDs are not specific to stereoscopic presentation and do not differ from those caused by desk-top CRT display.

Purpose: The authors retrospectively analyzed changes in the retinal nerve fiber layer in patients with idiopathic intracranial hypertension and studied their relation to visual field loss to determine the clinical usefulness of retinal nerve fiber analysis in the clinical management of patients with papilledema., Methods: Retinal nerve fiber layer photographs and visual fields from 36 eyes of 21 patients with papilledema due to idiopathic intracranial hypertension were analyzed for abnormalities in a masked fashion., Results: Nerve fiber layer changes were found in 67% of eyes studied. Superior areas within the nerve fiber layer were affected 5.4 times more frequently than inferior regions. Visual field loss was more prevalent in eyes with diffuse nerve fiber layer loss (89%) than in eyes with slit defects (29%). The location of the nerve fiber layer changes correlated with corresponding areas of visual field loss. Nerve fiber layer changes were as common in mild to moderate as in atrophic papilledema; however, slit defects predominated in patients with mild to moderate papilledema, and diffuse loss predominated in atrophic papilledema., Conclusions: Changes in the retinal nerve fiber layer observed in patients with idiopathic intracranial hypertension provide objective information regarding the status of their optic nerve and may improve their clinical management.

A review of peripheral visual control of eye movements suggests that such control may be easier if the direction of the extrafoveal locus used is orthogonal rather than radial to the direction of target motion. When the extrafoveal locus lies parallel (radial) to the direction of target or eye motion, artificial feedback is usually required to avoid reflexive foveation. These findings have important implications for training eccentric viewing in low vision patients with central scotomata.

Reflected glare often interferes with vision. Since such glare is usually polarized it can be controlled with polarizers. The use of polarized filters to eliminate vertically polarized glare from blackboards and glossy printed material is presented. Practical means for the construction of such filters are discussed.