Binocular summation to gratings in the peripheral field in older subjects is spatial frequency dependent.
OBJECTIVE
Binocular summation for contrast detection in the fovea is lower in older normal subjects. At present, no binocular summation data exist for contrast detection in older subjects in the peripheral field.


METHODS
Monocular and binocular contrast thresholds were measured for sine-wave gratings of 1 c/deg (F1) and 4 c/deg (F4) in the fovea in young and older visually normal subjects. Measurements were also obtained at 8 degrees in the superior field for gratings of 1 c/deg (P1) and 4 c/deg (P4).


RESULTS
Binocular summation ratios in young subjects at the fovea and periphery were not statistically different at either spatial frequency. In older subjects, analysis of the relevant conditions showed significantly lower summation ratios for: P4/F4 combination (p = 0.05), and P4/P1 combination (p = 0.03). No significant differences existed for F1/P1 and F1/F4 combinations (p > 0.05).


CONCLUSIONS
Lowest binocular summation ratio is shown with older subjects for gratings of 4 c/deg in the periphery (P4). Further analysis suggests the possibility that this is due to a larger relative loss in binocular sensitivity. Data are discussed in terms of selective loss of binocular neurons mediating peripheral sensitivity in the ageing eye.
Pardhan
Shahina
S
Department of Optometry and Ophthalmic Dispensing, Anglia Polytechnic University, East Road, Cambridge CB1 1PT, UK. s.pardhan@apu.ac.uk
Whitaker
Angela
A
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D005584:Fovea Centralis / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D012684:Sensory Thresholds; D015348:Vision, Binocular / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*