Purchase this article with an account.
L.A. Ostrin, A. Glasser; Edinger-Westphal Stimulated Accommodation in Rhesus Monkeys is Not Affected by Phenylephrine . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2730.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Phenylephrine is used to dilate the iris without cycloplegia through alpha adrenergic stimulation of the iris dilator muscle. Sympathetic stimulation of the ciliary muscle is believed to be inhibitory, thereby decreasing accommodative amplitude. Investigations in humans have suggested some loss of functional accommodation after phenylephrine administration. However, it is unclear whether this loss is due to direct action of phenylephrine on the ciliary muscle or secondary optical factors associated with the induced mydriasis. The aim of this study was to determine if Edinger-Westphal (EW) stimulated accommodation is affected by direct action of phenylephrine on the ciliary muscle in rhesus monkeys. Methods: The time course and extent of mydriasis was determined by videographic pupilography after 2 drops of 10% phenylephrine in 10 normal rhesus monkeys. Static and dynamic EW stimulated accommodative responses were studied in 5 iridectomized rhesus monkeys before and after instillation of 2 drops of 10% phenylephrine. The maximum EW stimulated accommodative amplitude was measured with a Hartinger coincidence refractometer to determine if amplitude was affected. Dynamic accommodative responses were measured with infrared (IR) photorefraction and functions were fitted to the data to determine peak velocity vs accommodative response relationships. Results: Maximum pupil dilation of 53% ± 12% occurred 15 minutes after phenylephrine administration. In the iridectomized monkeys, post-phenylephrine Hartinger measured accommodative amplitudes were similar to pre-phenylephrine amplitudes (pre: 11.71D ± 2.05D, post: 11.74D ± 1.75D; t = 0.13, p = 0.89), and were achieved with the same stimulus current amplitudes. Dynamic analysis of the accommodative responses measured with IR photorefraction showed linear peak velocity vs accommodative amplitude relationships that were similar before and after phenylephrine (slope pre: 2.31 ± 0.76, slope post: 2.04 ± 0.60; t = 0.55, p = 0.60). Conclusions: These results indicate that EW stimulated accommodative amplitude and dynamics in anesthetized, iridectomized rhesus monkeys are not influenced by alpha adrenergic stimulation. The results suggest that phenylephrine does not reduce EW stimulated accommodative amplitude or alter EW stimulated accommodative dynamics in rhesus monkeys by a direct action on the ciliary muscle.
This PDF is available to Subscribers Only