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[Effect of stimulus size on binocular summation within the binocular visual field]
A Wakayama1, C Matsumoto, A Iwagaki
1Department of Ophthalmology, Kinki University School of Medicine, 377-2 Ohno-higashi, Osaka-Sayama 589-8511, Japan.
Purpose:
To study the influence of stimulus sizes on binocular summation using the modified Octopus 201 combined with a space synoptophore.
Methods:
Four normal subjects, aged 21 to 26 were tested. Using the SARGON program, we designed a new program to test 37 points in the central 6 degrees visual field. Sensitivity of the central 6 degrees visual field under monocular and binocular conditions was measured while the fusion patterns were displayed on the space synoptophore. The visual fields were measured at stimulus sizes 1, 3, and 5.
Results:
The visual sensitivity under binocular conditions was higher than under monocular conditions for all the stimulus sizes. Binocular summation for stimulus size 1 was present in a flat form, for stimulus size 3 in a convex form, and for stimulus size 5 in a concave form in the central 6 degrees visual field.
Conclusion:
Binocular summation differed in stimulus size and retinal eccentricity. Binocular summation for stimulus size 3 increased in the fovea and it increased for stimulus size 5 in the peripheral area in the central 6 degrees visual field.