Dynamic accommodation in rhesus monkeys

The dynamics of Edinger-Westphal (EW) stimulated accommodation were studied in two young rhesus monkeys to understand the relationships between accommodative amplitude and rates of accommodation and disaccommodation. Accommodative responses were recorded with infrared photorefraction at five different amplitudes spanning the full EW stimulated accommodative range available to each eye. Combined exponential and polynomial functions were fit to the accommodation and disaccommodation responses. Derivatives of these functions provided the maximum rates of accommodation and disaccommodation as well as time constants for each amplitude. Maximum rates of EW stimulated accommodation and disaccommodation were found to increase linearly with amplitudes from 0.58 to 17.41 D in the two monkeys. The results suggests that the rate of EW stimulated accommodation is dictated by the amplitude. We conclude that if dynamic accommodative responses are to be compared in monkeys of different ages it is necessary to compare responses for the same accommodative amplitudes in order to draw conclusions about age related changes.