In vivo videography of the rhesus monkey accommodative apparatus. Age-related loss of ciliary muscle response to central stimulation
M. W. Neider, K. Crawford, P. L. Kaufman and L. Z. Bito
Department of Ophthalmology, University of Wisconsin, Madison.
Fourteen rhesus monkeys, aged 1 to 24 years, underwent permanent
implantation of a bipolar stimulating electrode into the Edinger-Westphal
nucleus and complete unilateral or bilateral iridectomy. Slit-lamp
Scheimpflug videography of the lens and slit-lamp goniovideography of the
lens equator, zonule, and ciliary body allowed direct real-time observation
and video recording of the movements of these structures during centrally
stimulated accommodation and during disaccommodation. Scalloping of the
lens capsule at the zonular insertion sites was clearly visible during
disaccommodation and even during accommodation when the zonules were
folded. During accommodation, the lens became axially thicker, the ciliary
ring narrowed, and, at high levels of accommodation, the zonular fibers
slackened and even folded and the lens moved downward. With increasing age
and concomitantly decreasing accommodative amplitude, these excursions all
diminished, so that in the oldest animals, they were very minimal or
absent. Maximum centrally stimulated accommodative amplitude declined with
age on a time scale similar to that for cholinomimetic drug-induced
accommodation in the rhesus monkey and voluntary accommodation in the
human.
