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Purpose: Glaucoma is a progressive optic neuropathy that damages retinal ganglion cells and a neurodegenerative disease as it a􀀀ects neural structures throughout the brain. In this study, we examined binocular rivalry responses in patients with early glaucoma in order to probe the function of stimulus-specific cortical areas involved in face perception. Methods: Participants included 14 individuals (10 females, mean age 65 ± 7 years) with early pre-perimetric glaucoma and 14 age-matched healthy controls (7 females, mean age 59±11 years). The 2 groups were equivalent in visual acuity and stereo-acuity. Three binocular rivalry stimulus pairs were used: (1) real face/house, (2) synthetic face/noise patch, and (3) synthetic face/spiral. For each stimulus pair, the images werematched in size and contrast level; they were viewed dichotically, and presented centrally and eccentrically at 3 degrees in the right (RH) and in the left hemifield (LH), respectively. The outcome measures were rivalry rate (i.e., perceptual switches/min) and time of exclusive dominance of each stimulus. Results: For the face/house stimulus pair, rivalry rate of the glaucoma group (11 ± 6 switches/min) was significantly lower than that of the control group (15 ± 5 switches/min), but only in the LH location. The face dominated longer than the house in the LH for both groups. Likewise, for the synthetic face/noise patch stimulus pair, rivalry rate of the glaucoma group (11 ± 6 switches/min) was lower than that of the control group (16 ± 7 switches/min) in the LH, but the di􀀀erence failed to reach significance. Interestingly, the mixed percept dominated less in glaucoma than in the control group. For the synthetic face/spiral stimulus pair, the glaucoma group had lower rivalry rate at all 3 stimulus locations. Conclusion: This study reveals atypical responses to faces during binocular rivalry in patients with early glaucoma. The results may be suggestive of early neurodegeneration a􀀀ecting stimulus-specific neural structures involved in face processing starting in the pre-perimetric phase of the disease. [ABSTRACT FROM AUTHOR]

For normally sighted observers, the centre of the macula—the fovea—provides the sharpest vision and serves as the reference point for the oculomotor system. Typically, healthy observers have precise oculomotor control and binocular visual performance that is superior to monocular performance. These functions are disturbed in patients with macular disease who lose foveal vision. An adaptation to central vision loss is the development of a preferred retinal locus (PRL) in the functional eccentric retina, which is determined with a fixation task during monocular viewing. Macular disease often affects the two eyes unequally, but its impact on binocular function and fixational control is poorly understood. Given that patients' natural viewing condition is binocular, the aim of this article was to review current research on binocular visual function and fixational oculomotor control in macular disease. Our findings reveal that there is no overall binocular gain across a range of visual functions, although clear evidence exists for subgroups of patients who exhibit binocular summation or binocular inhibition, depending on the clinical characteristics of their two eyes. The monocular PRL of the better eye has different characteristics from that of the worse eye, but during binocular viewing the PRL of the better eye drives fixational control and may serve as the new reference position for the oculomotor system. We conclude that evaluating binocular function in patients with macular disease reveals important clinical aspects that otherwise cannot be determined solely from examining monocular functions, and can lead to better disease management and interventions. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the plasticity of fixation in patients with central vision loss. Most of these patients use preferred retinal loci (PRLs) in the healthy eccentric part of the retina to fixate, but fixation stability and retinal location are not always optimal for best visual performance. This study examined whether fixation stability and a new PRL location can be trained and whether these changes in ocular motor control transfer into better reading performance. Six patients with age-related macular degeneration participated in the study. Fixation stability measurements, microperimetry, and auditory biofeedback training were performed with the MP-1 microperimeter. The auditory biofeedback was used during five 1-h long training sessions to improve fixation and relocate the PRL. Fixation location and stability were recorded while viewing four different targets: a cross, a letter, a word, and a nine-cycle radial grating. Visual acuity was assessed with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and reading performance with the MNRead test. The results showed that all patients developed a new PRL in an optimal location for reading, and they were able to use it consistently while viewing different targets. Fixation stability improved 53% after training. Learning transferred to the old PRL even though fixation stability at this location was not trained. All these improvements in ocular motor control translated into better reading performance: reading speed improved 38% and reading acuity and critical print size gained two lines. We conclude that the ability of the ocular motor system to fixate is flexible in patients with central vision loss: a new PRL can be trained, fixation stability can be improved, and learning transfers to an untrained location. These gains in ocular motor control result in better visual performance. This property can be successfully used to optimize the residual vision of patients with central vision loss. [ABSTRACT FROM PUBLISHER]

The effects of stimulus eccentricity, visual angle, and fixation on linear vection (sensation of self-translation induced by large moving scenes) were examined in healthy young people. Three aspects of vection were measured: latency, total vection time, and strength. The results showed that when peripheral and central stimuli are equal in area, they induce similar vection, but only when they are presented with a fixation cross. When presented without a fixation cross, peripheral stimuli are more effective in inducing vection than central stimuli. In addition, central stimuli with a fixation cross elicited more vection than central stimuli without a fixation cross. Fixation had no influence on the vection induced by peripheral stimuli. These findings indicate that statements about the role of central and peripheral stimuli of equal area in inducing vection should be made only in conjunction with reports about whether these stimuli are presented with or without fixation. [ABSTRACT FROM AUTHOR]

The sources of the reduced fixation stability exhibited by patients with central vision loss in the light are relatively well understood, but we have no information on how they control eye position in complete darkness, in the absence of visual error signals. We therefore explored the effect of visual feedback on eye position stability by testing patients with age-related macular degeneration (AMD) and controls with normal vision in the light and in complete darkness. Nine patients (ages 67 to 92 years) and 16 controls (ages 16 to 74 years) were tested binocularly in the light and in complete darkness while remembering the location of a now invisible target. Binocular eye position was recorded with a video-based eye tracker. Results show that eye position stability both in the light and in the dark is worse for patients than for controls and that, for the two groups, eye position stability in the dark is, on average, 5.9 times worse than in the light. Large instability of fixation in patients with AMD was found even in absolute darkness when the scotoma cannot impair vision. These data reflect permanent changes in the oculomotor reference of patients with AMD., Competing Interests: The authors report no conflicts of interest and have no proprietary interest in any of the materials mentioned in this article.

Purpose: The authors present a computer-based method for evaluating the visual acuity of patients with age-related macular degeneration (AMD). It incorporates four features known to improve visual acuity: high contrast, white optotypes on a black background to reduce intraocular scatter, proportional layout to reduce the effects of crowding, and multiple optotypes to minimize the effects of fixation instability and to maximize the likelihood of optotype detection., Methods: Experiment 1 evaluated the best-eye acuity of 24 patients with AMD using the ETDRS chart and three versions of the Tumbling E acuity test: multiple black optotypes on a white background, single white optotype on a black background, and multiple white optotypes on a black background. Experiment 2 compared the two White E optotype tests with the ETDRS in patients with AMD, and Experiment 3 measured probability summation in persons with normal vision., Results: Multiple white optotypes on a black background yielded the highest acuity estimates and the ETDRS the lowest. The Single E test yielded a lower estimate of acuity than the two Multiple E tests. The effect of polarity-white on black was better than black on white-was consistent with results found in persons with healthy retinas. For patients with AMD, acuity measured with the Multiple E test was independent of that measured with the ETDRS, but acuity measured with the Single E test decreased as acuity worsened. For the participants with normal vision, the differences between the Multiple and Single E tests were within the known limits of test-retest variability., Conclusions: The multiple-optotype, reversed-polarity test provides a measure of the optimal visual acuity of which a person is capable and, in this sense, may be a useful tool for assessing rehabilitation progress.

The effects of stimulus eccentricity, visual angle, and fixation on linear vection (sensation of self-translation induced by large moving scenes) were examined in healthy young people. Three aspects of vection were measured: latency, total vection time, and strength. The results showed that when peripheral and central stimuli are equal in area, they induce similar vection, but only when they are presented with a fixation cross. When presented without a fixation cross, peripheral stimuli are more effective in inducing vection than central stimuli. In addition, central stimuli with a fixation cross elicited more vection than central stimuli without a fixation cross. Fixation had no influence on the vection induced by peripheral stimuli. These findings indicate that statements about the role of central and peripheral stimuli of equal area in inducing vection should be made only in conjunction with reports about whether these stimuli are presented with or without fixation.