Edinger-Westphal stimulated accommodation in rhesus monkeys: Dynamics, biometry and aberrometry

Purpose. The aims of the experiments presented here are (i) to characterize Edinger-Westphal (EW) stimulated accommodative dynamics in rhesus monkeys by using objective methods to describe the accommodative response, (ii) to study the effects of repeated accommodation on response dynamics and fatiguing in rhesus monkeys and humans, (iii) to ascertain the interrelationships between accommodative refractive and biometric changes and (iv) to study changes in ocular aberrations during accommodation over the entire lens diameter in vivo in rhesus monkeys.; Methods. Accommodation was centrally stimulated in anesthetized monkeys which had undergone prior, bilateral complete iridectomies, by stimulating the EW nucleus through a permanent, indwelling, electrode and refractive changes were recorded with infrared photorefraction.; Results and inferences. Experiment 1: Peak velocities of accommodation and disaccommodation increased linearly with amplitude and peak velocity of disaccommodation was approximately 3 times faster than peak velocity of accommodation. Experiment 2: Accommodative amplitude, maintenance and main sequence ratios changed in some of the stimulus paradigms in the monkeys. Experiment 3: Dynamic changes in biometry are linearly correlated to refractive changes such that lens thickness increases by 0.063 mm/D, anterior chamber depth decreases by 0.046 mm/D and anterior segment length (anterior chamber depth + lens thickness) increases by 0.02 mm/D of accommodation. Experiment 4: Root mean square error of the total measured aberrations excluding defocus, increased systematically with increasing accommodation from about 1 to 3.5 microns.; Conclusions. Dynamics of EW stimulated accommodation in adolescent monkeys have been characterized using objective methods to elicit peak velocity versus amplitude relationships. Dynamic measurements show that while accommodation can be produced repeatedly, some EW stimulation paradigms in monkeys result in changes in the accommodative response characteristics that may reflect fatigue. Correlated biometric and refractive dynamic measurements provide new information, such as per diopter movements in lens surfaces and wavefront aberration measurements provide information on spatially variant changes in lens power. These studies have characterized dynamic, optical and biometric accommodative changes with EW stimulated accommodation, providing new knowledge about the dynamics of accommodation and how the lens changes shape during accommodation in rhesus monkeys.* (Abstract shortened by UMI.); *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat; QuickTime.