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M. Wendt, A. Glasser; Intravenous Pilocarpine Stimulated Accommodation in Rhesus Monkeys. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2794.
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Topically administered pilocarpine has been used to stimulate accommodation in both humans and monkeys. However, the concentrations of pilocarpine used, the methods of administration and the results achieved have varied. Here we examine the effectiveness of intravenous (IV) pilocarpine administration in stimulating accommodation in anesthetized rhesus monkeys.
Experiments were performed on 6 anesthetized rhesus monkeys aged 5 to 16 years with iridectomized eyes. Maximum accommodation was stimulated with a 2% pilocarpine solution maintained topically on the cornea for at least 30 minutes in a specially designed ocular perfusion lens. In IV experiments, pilocarpine was given as either boluses ranging from 0.25 mg/kg to 2 mg/kg over 30 seconds or as boluses followed by constant infusion with rates of between 3.06 mg/kg/hr and 12.25 mg/kg/hr. Accommodative responses were measured dynamically with photorefraction in one eye and continuous ultrasound biometry in the other eye.
Constant 2% topically applied pilocarpine in the perfusion lens produced 12.7D ± 2.8 (mean ± SD). A mean accommodative amplitude of 9.2D ± 1.8 (mean ± SD) was achieved with 1.0 mg/kg IV boluses. IV pilocarpine boluses achieved nearly maximal accommodation at least ten times faster than topical methods. Responses to IV pilocarpine boluses had short, dose-dependent durations which were typically less than 5 minutes for sub-maximal doses. IV bolus doses required to achieve maximum accommodation ranged from 0.25 mg/kg to 1.0 mg/kg. IV pilocarpine boluses cause anterior movement of the anterior lens surface, posterior movement of the posterior lens surface, and slight net anterior movements of the entire lens. Constant IV pilocarpine infusions achieved sustained accommodation for more than 45 minutes and were between 57% and 96% of maximum accommodation achieved for the same monkey using constant topical perfusion.
IV pilocarpine boluses cause rapid, short duration responses. Sustained accommodation can be achieved with IV boluses followed by constant infusion. IV pilocarpine is a reliable method of producing a normal, sustained, and nearly maximal accommodative response in anesthetized monkeys.
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