Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

Abstract

During accommodation, the refractive changes occur when the ciliary muscle contracts, releasing resting zonular tension and allowing the lens capsule to mold the lens into an accommodated form. This results in centripetal movement of the ciliary processes and lens edge. The goal of this study was to understand the relationship between accommodative refractive changes, ciliary process movements and lens edge movements during Edinger-Westphal (EW) and pharmacologically stimulated accommodation in adolescent rhesus monkeys. Experiments were performed on one eye each of three rhesus monkeys with permanent indwelling electrodes in the EW nucleus of the midbrain. EW stimulated accommodative refractive changes were measured with infrared photorefraction, and ciliary process and lens edge movements were measured with slit-lamp goniovideography on the temporal aspect of the eye. Images were recorded on the nasal aspect for one eye during EW stimulation. Image analysis was performed off-line at 30 Hz to determine refractive changes and ciliary body and lens edge movements during EW stimulated accommodation and after carbachol iontophoresis to determine drug induced accommodative movements. Maximum EW stimulated accommodation was 7.36 ± 0.49 D and pharmacologically stimulated accommodation was 14.44 ± 1.21 D. During EW stimulated accommodation, the ciliary processes and lens edge moved centripetally linearly by 0.030 ± 0.001 mm/D and 0.027 ± 0.001 mm/D, with a total movement of 0.219 ± 0.034 mm and 0.189 ± 0.023 mm, respectively. There was no significant nasal/temporal difference in ciliary process or lens edge movements. 30-40 minutes after pharmacologically stimulated accommodation, the ciliary processes moved centripetally a total of 0.411 ± 0.048 mm, or 0.030 ± 0.005 mm/D, and the lens edge moved centripetally 0.258 ± 0.014 mm, or 0.019 ± 0.003 mm/D. The peaks and valleys of the ciliary processes moved by similar amounts during both supramaximal EW and pharmacologically stimulated accommodation. In conclusion, this study shows, for the first time, that the ciliary processes and lens edge move centripetally, linearly with refraction during EW stimulated accommodation. During pharmacological stimulation, the ciliary processes move to a greater extent than the lens edge, confirming that in adolescent monkeys, lens movement limits the accommodative optical change in the eye.* corresponding author: aglasser@uh.edu.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Accommodation is a dioptric change in power of the eye to focus on objects at different distances. In the unaccommod...

Autonomic Control of the Eye

“…Also, anatomical investigations in primates have revealed much about the sources of afferents to the EWpg that mediate accommodation. A number of studies have shown that electrical microstimulation in or immediately adjacent to the EW evokes ocular accommodation in primates (24, 61, 68, 118, 166, 173, 279, 280, 410, 418);. These results of EW stimulation are also consistent with studies in which electrical stimulation of the ciliary ganglion or nerves produced similar increases in accommodation in cats (232, 308).…”

Quantification of Age-Related and per Diopter Accommodative Changes of the Lens and Ciliary Muscle in the Emmetropic Human Eye

“…[9][10][11][12][13][14] Edinger-Westphal and pharmacologically stimulated accommodation in rhesus monkeys demonstrate that the lens is the limiting factor in the accommodative response and that the ciliary muscle retains its ability to contract well beyond the onset of presbyopia. [9][10][11][15][16][17] Only within the last decade have improvements in noninvasive imaging technology allowed for similar studies in humans. To date, no study has undertaken a per diopter analysis of anatomical changes in both the crystalline lens and ciliary muscle in a single cohort of human subjects.…”

Topical and intravenous pilocarpine stimulated accommodation in anesthetized rhesus monkeys

“…The study of aspects of accommodation and presbyopia in rhesus monkeys relies on the ability to induce accommodation. While this can be accomplished behaviorally in awake monkeys (Bossong et al, 2009), the ability to scrutinize and image different aspects of the accommodative movements in the eyes often relies on contact imaging techniques such as ultrasound biomicroscopy (Croft et al, 2009) and gonioscopy (Ostrin and Glasser, 2007; Rosales et al, 2008; Wendt et al, 2008) that require working on anesthetized monkeys. It is therefore necessary to be able to induce accommodation in anesthetized monkeys in a reliable and reproducible manner.…”