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Glaucoma is considered a progressive optic neuropathy because of the damage and death of the retinal ganglion cells. It is also a neurodegenerative disease because it affects neural structures in the visual system and beyond, including the corpus callosum–the largest white matter structure involved in inter-hemispheric transfer of information. In this study we probed the dysfunction of the inter-hemispheric processing in patients with mild glaucoma using the phenomenon of binocular rivalry. Patients with mild glaucoma and no measurable visual field defects and age-matched controls underwent a thorough visual assessment. Then they participated in a series of psychophysical tests designed to examine the binocular rivalry derived from intra- and inter-hemispheric processing. Static horizontal and vertical sinewave gratings were presented dichoptically using a double-mirror stereoscope in 3 locations: centrally, to probe inter-hemispheric processing, and peripherally to the left or to the right, to probe intra-hemispheric processing. Although the two groups were matched in functional measures, rivalry rate of the glaucoma group was significantly lower than that of the control group for the central location, but not for the peripheral location. These results were driven mainly by the patients with normal tension glaucoma whose average rivalry rate for the central location (from which information reaches the two hemispheres) was almost half (46% lower) that of the controls. These results indicate a dysfunction in inter-hemispheric transfer in mild glaucoma that can be detected behaviourally before any changes in standard functional measures. [ABSTRACT FROM AUTHOR]

Glaucoma is both a progressive optic neuropathy and a neurodegenerative disease affecting structures in the primary visual pathway. Other vision-associated areas may also be affected, including the corpus callosum which is involved in inter-hemispheric transfer. This study evaluated dominance wave propagation during binocular rivalry to probe the efficacy of the inter-hemispheric transfer in 20 patients with mild open angle glaucoma and 25 age-matched controls. The two groups were matched for functional measures such as stereo-acuity, binocular visual acuity, and visual field mean deviation. Monocular functional and structural measures were equivalent for the left and right eye of each participant. Using Wilson et al.'s travelling wave paradigm [Nature, 412 (2001) 907-910], intra- and inter-hemispheric failure rates of traveling wave transmission and the travelling wave propagation times were recorded for the two groups. For the control group, the wave propagation failure rate was significantly greater for the inter- than for the intra-hemispheric condition, but for the glaucoma group, the failure rates were equally high for the two conditions. The wave propagation time was significantly longer for the inter- than for the intra-hemispheric condition for the control group, while the opposite was true for the glaucoma group. These results reveal changes in the wave dynamics of rivalry dominance in patients with mild glaucoma who otherwise have normal performance on standard functional measures. [ABSTRACT FROM AUTHOR]

Purpose In this study we evaluated the reading accessibility index ( ACC) and a quality of reading grid as assessment tools for reading and as outcome measures for reading rehabilitation of patients with central vision loss. Methods Reading performances on the MNRead chart () were reviewed from our research database. Participants were 24 controls with normal vision [mean age: 34 ( SD, 14) years] and 61 patients with bilateral central vision loss [mean age: 81 ( SD, 9) years] among which a subgroup of 18 patients [mean age, 76 ( SD, 13) years] had undergone perceptual learning training for reading rehabilitation. The outcome measures were maximum reading speed, reading acuity, critical print size, ACC, and the reading quality. A reading quality grid that classified reading speed as spot, slow, functional, or fluent and print size as small, regular, medium, or large was used. All reading speed values were normalised (i.e., divided by 200, the average reading speed in young adults with normal vision measured with the MNRead). Results The ACC was associated perfectly with the maximum reading speed in the control group ( r22 = 0.99, P < 0.001) and strongly with all parameters of reading in the patient group (smallest r value: r59 = −0.66, P < 0.001). For patients with central vision loss, reading was functional for large print, but slow for medium print and spot for regular print. For some patients with the same ACC values, the quality of reading grid revealed important performance differences. For the subgroup ( n = 18) of patients who were trained, the ACC revealed a greater effect of training than the other three parameters of reading, and although there were statistically significant improvements across all print size categories, a qualitative improvement in reading was noticed only for the medium print sizes. Conclusions The ACC is a good measure of reading performance in patients with central vision loss. Examining reading quality for different print size categories can provide a more detailed picture of reading impairment and should be considered as an outcome for rehabilitation in addition to the ACC. [ABSTRACT FROM AUTHOR]

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]

Abstract: This study examined two aspects of binocular function in patients with age-related macular degeneration (AMD): summation/inhibition of visual acuity and rivalry. The performance of 17 patients with AMD was compared with that of 17 elderly controls and 21 young people. Monocular and binocular acuities were measured using a multiple-E optotype test. Binocular ratios, defined as the better-eye acuity divided by the binocular acuity, were calculated. We also measured eye dominance during rivalry (proportion of time the participants reported perceiving the input to each eye) and rivalry rates (number of alternations per minute). The results showed that while overall binocular ratios were similar for the three groups, the frequency distributions of people who experienced inhibition, equality or summation were different for the young and AMD groups. In the rivalry test, patients experienced more piecemeal perception than the elderly and young controls, but time dominance from the better-seeing eye was comparable for the three groups. Rivalry rates decreased with age and further with pathology. Moreover, rivalry time dominance of the worse-seeing eye was negatively correlated with interocular acuity differences for the AMD group. [Copyright &y& Elsevier]

In order to evaluate the effect of the parafoveal area of the retina on smooth pursuit, we compared the horizontal smooth pursuit of visible and amodally completed stimuli in people with central vision loss and controls. In the amodally completed stimuli, a black mask covered the bottom vertex of a moving diamond which is the feature whose movement participants had to track. Both the visible and the amodally completed stimuli moved along regular and irregular sinusoidal motion paths. Our results show that people with central vision loss are able to track a perceptually completed moving stimulus albeit with lower gain, larger tracking errors, and more saccadic eye movements than people with normal vision. Just as the controls, however, people with central vision do better in the no mask condition showing that visual feedback from eccentric vision can improve performance. • We evaluated the effect of the parafoveal area of the retina on smooth pursuit. • Stimuli were visible and amodally completed moving diamonds. • Completed figures can be tracked using information from peripheral retina. • Visual feedback from eccentric vision can be used to improve performance. [ABSTRACT FROM AUTHOR]

Purpose: This study reports the repeatability of 20 s‐duration fixation stability measurements recorded with the Macular Integrity Assessment (MAIA) microperimeter in patients with central vision loss, in contrast to the Nidek MP1 microperimeter. Methods: Fixation stability was recorded in 39 eyes of 25 patients with macular disease using MAIA and the MP1 for 20 s intervals, twice for each eye, with each instrument. Twenty eyes were identified as the better eye (BE) and 19 eyes as the worse eye (WE). Fixation stability was quantified with the 95% bivariate contour ellipse area (BCEA), logarithmically transformed. Bland‐Altman plots were used to determine the 95% limits of agreement. Results: For MAIA, the 95% limits of agreement were ±0.84 log deg2 for the BE and ±0.66 log deg2 for the WE. Similarly, for the MP1 these limits were ±0.48 log deg2 for the BE and ±0.72 log deg2 for the WE. Inter‐device repeatability was modest, ±1.09 log deg2 for the BE and ±1.01 log deg2 for the WE, and a proportional bias was detected. Occasionally, MAIA did not register all the expected number of data points, and included far outliers in the BCEA calculation; the inter‐device repeatability did not improve when these outliers were removed. Conclusions: Repeatability of 20 s‐duration fixation stability examination in patients with central vision loss is specific to the instrument used. We recommend that only data from same type of microperimeter with the same fixation duration should be compared when using fixation stability as an outcome measure to monitor disease progression, effect of treatment or in clinical trials. [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]

Purpose: There are conflicting reports as to whether there is a binocular advantage or disadvantage when reading with central vision loss. This study examined binocular reading summation in patients with macular degeneration. Methods: Seventy‐one patients with bilateral central vision loss [mean age: 63 (S.D. = 21) years] participated. Reading performances during binocular and monocular viewing with the better eye (i.e., the eye with the best monocular visual acuity) were evaluated using different versions of the Italian MNREAD reading chart (www.precision‐vision.com). Fixation stability and preferred retinal loci (PRLs) were recorded monocularly for each eye. The overall sample was split into inhibition, equality, and summation groups based on the binocular ratio (i.e., binocular/monocular) of the maximum reading speed. Results: 41% of patients experienced binocular inhibition, 42% summation, and 17% equality. Binocular reading speed of the inhibition group was approximately 30 words per minute slower than those of the equality and summation groups, although the inhibition group had the best visual acuity. These patients generally had monocular PRLs in non‐corresponding locations temporal or nasal to the scotoma, had the largest interocular acuity difference and lacked residual stereopsis. The three groups did not differ in fixational control, contrast sensitivity or critical print size. Conclusions: Equal proportions of patients with central vision loss show binocular reading summation and inhibition. Patients with binocular reading inhibition have poorer reading performance and different clinical characteristics than those with binocular reading summation and equality. [ABSTRACT FROM AUTHOR]