Dynamics of Refractive Changes and Lens and Ciliary Body Movements in Rhesus Monkey Eyes During Edinger-Westphal Nucleus Stimulated Accommodation

Few studies have explored dynamic changes in the accommodative elements of the eye in relation to presbyopia (Schaeffel, et al., 1993; Beers & Van Der Heijde, 1994, 1996; Kaufman, et al., 1997). In the normal human eye the only aspect of the accommodative apparatus readily accessible for dynamic studies is the lens. Although measurements of dynamic changes in lens thickness have been made (Beers & Van Der Heijde, 1994, 1996), they provide no information on the relationship between movements of the extralenticular accommodative apparatus and the refractive changes in the eye or how these relationships changes with age and presbyopia. Recent work has shown age changes in movements of the accommodative elements of the iridectomized rhesus monkey eye (Kaufman, et al, 1997). Further studies of age changes in the extralenticular accommodative apparatus are underway and we present for the first time, results from this work relating mechanical movements of the extralenticular accommodative apparatus to refractive and lenticular changes in the eyes of young accommodating rhesus monkeys. This work aims to characterize and describe normal dynamic relationships between the extralenticular accommodative apparatus and the lens. Rhesus monkeys are ideal subjects for these studies since young animals have high accommodative amplitudes, they develop presbyopia with the same relative age course as humans, and surgical removal of the iris and implantation of stimulating electrodes in the midbrain facilitates imaging of the ciliary body and lens equator during electrically stimulated accommodation (Crawford, et al., 1989; Neider, et al., 1990).