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A comparison of binocular summation in the peripheral visual field in young and older patients.

PURPOSE
To measure binocular and monocular thresholds to a light detection task in order to investigate binocular summation in the central and peripheral visual fields. The study also aims to investigate any differences in the magnitude of binocular summation in young and older subjects with healthy eyes.


METHODS
Binocular and monocular thresholds were measured at eccentricities of 0, 5, 15, 25 and 40 degrees nasally and temporally, using the Humphrey Field Analyser. Binocular summation ratios were computed as the binocular sensitivity divided by the "best" monocular sensitivity.


RESULTS
Binocular and monocular sensitivities declined with increasing eccentricity. Binocular summation ratios were shown to be significantly higher for the younger group compared to the older group at all eccentricities.


CONCLUSIONS
Using this test, the binocular performance is shown to be lower for the older group at all eccentricities. Results are discussed in terms of age-related cortical cell loss and increased monocular sensitivity difference.