VERGENCE ADAPTATION AND SENESCENCE

Purpose. The characteristics of prism adaptation have been evaluated b y many previous studies but most have been performed on young subjects (typically 18 to 35 years of age). Because little information is avai lable regarding the effect of age on vergence adaptation, we assessed prism adaptation on 25 visually normal subjects across a wide age rang e (19 to 85 years) for both convergent and divergent induced dispariti es. 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 contro lled with an Apple IIe microcomputer through a CIL Microsystems interf ace. Results. Prism adaptation was shown to be present in all age grou ps, with convergence showing a greater amplitude than divergence. Howe ver, the magnitude of adaptation declined significantly as a function of increasing age at a rate of approximately 0.6% per year. Conclusion . An adaptation mechanism is present in all subjects but it operates w ith reduced gain in older subjects. The finding may explain the clinic al observation that older patients readily accept prismatic correction to control oculomotor imbalance.