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1From the Department of Ophthalmology and Visual Sciences, Wisconsin Regional Primate Research Center, and 3Biostatistics and Medical Informatics, University of Wisconsin, Madison, Wisconsin; and the 2College of Optometry, University of Houston, Houston, Texas.
PURPOSE. The underlying causes of presbyopia, and the functional relationship between the ciliary muscle and lens during aging are unclear. In the current study, these relationships were studied in rhesus monkeys, whose accommodative apparatus and age-related loss of accommodation are similar to those in humans.
METHODS. Centripetal ciliary body and lens equator movements were measured during accommodation in 28 eyes of 21 rhesus monkeys (ages, 5.726 years) by goniovideography. Ultrasound biomicroscopy was performed in 21 eyes of 17 monkeys. Narrowing of the angle between the anterior aspect of the ciliary body and the inner aspect of the cornea was used as a surrogate indicator of forward ciliary body movement during accommodation.
RESULTS. Average centripetal ciliary body movement in older eyes (age
17 years, n = 16) was
20% (0.09 mm) less than in young eyes (age, 610 years, n = 6), but not enough to explain the 60% (0.21 mm) loss in centripetal lens movement nor the 76% (10.2 D) loss in accommodative amplitude. Average forward ciliary body movement was 67% (49°) less in older (n = 11) versus young (n = 6) eyes. Maximum accommodative amplitude correlated significantly with the amplitude of centripetal lens movement (0.02 ± 0.003 mm/D; n = 28; P < 0.001) and with forward ciliary body movement (3.34 ± 0.54 deg/D; n = 21; P = 0.01).
CONCLUSIONS. Decreased lens movement with age could be in part secondary to extralenticular age-related changes, such as loss of ciliary body forward movement. Ciliary body centripetal movement may not be the limiting component in accommodation in the older eye.
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