Accommodation dynamics in aging rhesus monkeys

by which the eye focuses on near objects, is lost with increasing age in humans and monkeys. This pathophysiol-ogy, called presbyopia, is poorly understood. We studied aging-related changes in the dynamics of accommodation in rhesus monkeys aged 4–24 yr after total iridectomy and midbrain implantation of an electrode to permit visualization and stimulation, respectively, of the eye’s accommodative apparatus. Real-time video techniques were used to capture and quantify images of the ciliary body and lens. During accommodation in youth, ciliary body movement was bipha-sic, lens movement was monophasic, and both slowed as the structures approached their new steady-state positions. Disac-commodation occurred more rapidly for both ciliary body and lens, but with longer latent period, and slowed near the end point. With increasing age, the amplitude of lens and ciliar