Accommodative changes in lens diameter in rhesus monkeys. Investigative Ophthalmology and Visual Science

PURPOSE. Some debate surrounds the accommodative mecha-nism in primates, particularly whether the lens equatorial di-ameter increases or decreases during accommodation. This study has been undertaken to measure the relationship be-tween changes in lens diameter and refraction during accom-modation in rhesus monkeys. METHODS. Photorefraction was used to measure accommoda-tion, and goniovideography was used to measure accommoda-tive changes in lens diameter in the iridectomized eyes of two rhesus monkeys. Accommodation was stimulated through the full amplitude available to each eye by stimulation of the Edinger-Westphal nucleus of the brain. Dynamic measurement of refractive changes followed by dynamic measurements of changes in lens diameter for the same stimulus current ampli-tudes allow the relationship between refraction and lens diam