Purpose In glaucoma, visual field defects in the left and right eye may be non-overlapping, resulting in an intact binocular visual field. In clinical management, these patients are often considered to have normal vision. However, visual performance also relies on binocular processing. The aim of this study was to evaluate binocular visual functions in glaucoma patients with intact binocular visual field, normal visual acuity, and stereoscopy. Methods We measured in 10 glaucoma patients and 12 age-similar controls: (1) monocular and binocular contrast sensitivity functions (CSF) using a modified quick CSF test to assess binocular contrast summation, (2) dominance during rivalry, and (3) contrast ratio at balance point with a binocular phase combination test. A mirror stereoscope was used to combine the left and right eye image (each 10° horizontally by 12° vertically) on a display. Results Area under the monocular and binocular CSF was lower in glaucoma compared to healthy ( P < 0.001), but the binocular contrast summation ratio did not differ ( P = 0.30). For rivalry, the percentage of time of mixed percept was 9% versus 18% ( P = 0.056), the absolute difference of the percentage of time of dominance between the two eyes 19% versus 10% ( P = 0.075), and the rivalry rate 8.2 versus 12.1 switches per minute ( P = 0.017) for glaucoma and healthy, respectively. Median contrast ratio at balance point was 0.66 in glaucoma and 1.03 in controls ( P = 0.011). Conclusions Binocular visual information processing deficits can be found in glaucoma patients with intact binocular visual field, normal visual acuity, and stereoscopy.
Citation: João CAR, Scanferla L, Jansonius NM. Retinal contrast gain control and temporal modulation sensitivity across the visual field in glaucoma at photopic and mesopic light conditions. Invest Ophthalmol Vis Sci. 2019;60:4270-4276. https://doi.org/ 10.1167/iovs.19-27123 PURPOSE. Glaucoma affects many aspects of visual performance, including adaptation, and this may depend on ambient luminance. We determine the influence of glaucoma and luminance on temporal aspects of adaptation, specifically on contrast gain control and temporal modulation sensitivity (TMS).METHODS. This case-control study included 12 glaucoma patients and 25 age-similar controls (50-70 years). Threshold perimetry was performed with a minimized testing grid (fovea and four peripheral locations). Stimuli (Goldmann size III 50 ms increment/decrement) were presented on a time-varying background with sinusoidally-modulated luminance (amplitude 60%; frequency 0-30 Hz; mean background luminance, 1 and 100 cd/m 2 ). TMS (2.5-30 Hz) was measured in the same locations with a sinusoidally-modulated stimulus (Goldmann size IV, 334 ms) on a steady background (1 and 100 cd/m 2 ). RESULTS.In healthy subjects, contrast sensitivity decreased with increasing background modulation frequency and increased again at very high frequencies, indicating contrast gain control. Minimum sensitivity was located between 2.5 and 20 Hz, depending on luminance and eccentricity. In glaucoma patients, the same frequency dependency was found (P ¼ 0.12) but with an overall reduced sensitivity (P ¼ 1 3 10 À5 ), independent of luminance (P ¼ 0.20). Decrements differentiated better between glaucoma and healthy subjects than increments (P ¼ 0.004). TMS was reduced in glaucoma (P ¼ 5 3 10 À6 ) across all frequencies and luminance levels, with complete loss for high frequencies at 1 cd/m 2 .CONCLUSIONS. Contrast gain control is largely unaffected in glaucoma, suggesting intact amacrine cell function. Perimetry with decrements or a high-frequency stimulus on a lowluminance background seems best to differentiate between glaucoma and healthy subjects.
SIGNIFICANCE Retinal sensitivity decreases with age and age-related eye diseases. Peripheral retinal sensitivity may also be compromised if the refractive correction is not optimized for peripheral vision. PURPOSE This study aimed to determine the impact of using a peripheral refractive correction on perimetric thresholds and the influence of age and spherical equivalent on this impact. METHODS We measured, in 10 younger (20 to 30 years) and 10 older (58 to 72 years) healthy subjects, perimetric thresholds for Goldmann size III stimulus in several test locations along the horizontal meridian of the visual field (eccentricity, 0, ±10, and ±25°), with default central refractive correction and with peripheral refractive corrections as measured with a Hartmann-Shack wavefront sensor. We used analysis of variance to determine the effect of age and spherical equivalent (between-subject variables) and eccentricity and correction method (central vs. eccentricity specific; within-subject variables) on retinal sensitivity. RESULTS Retinal sensitivity was higher if the eyes were optimally corrected for the concerning test location ( P = .008), and the effect of this peripheral correction differed between the younger and older subjects (interaction term between group and correction method: P = .02), primarily because of more myopia in the younger group ( P = .003). The average improvement by applying peripheral corrections was 1.4 dB in the older subjects and 0.3 dB in the younger subjects. CONCLUSIONS Peripheral optical correction has a variable impact on retinal sensitivity, and therefore, assessment of retinal sensitivity may be more accurate if peripheral defocus and astigmatism are corrected.
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