Vergence adaptation and senescence.
OBJECTIVE
The characteristics of prism adaptation have been evaluated by many previous studies but most have been performed on young subjects (typically 18 to 35 years of age). Because little information is available regarding the effect of age on vergence adaptation, we assessed prism adaptation on 25 visually normal subjects across a wide age range (19 to 85 years) for both convergent and divergent induced disparities.


METHODS
A "flashed" (125 ms) Maddox rod procedure was used for distance fixation (5 m) over a 3.5 min adaptation period and a 2.5 min recovery period. Stimulus presentation and occlusion time were controlled with an Apple lle microcomputer through a ClL Microsystems interface.


RESULTS
Prism adaptation was shown to be present in all age groups, with convergence showing a greater amplitude than divergence. However, the magnitude of adaptation declined significantly as a function of increasing age at a rate of approximately 0.6% per year.


CONCLUSIONS
An adaptation mechanism is present in all subjects but it operates with reduced gain in older subjects. The finding may explain the clinical observation that older patients readily accept prismatic correction to control oculomotor imbalance.
Winn
B
B
Department of Optometry, University of Bradford, West Yorkshire, United Kingdom.
Gilmartin
B
B
Sculfor
D L
DL
Bamford
J C
JC
D000221:Adaptation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003290:Convergence, Ocular / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D015357:Vision Disparity / Q000502:physiology; D014787:Vision Tests