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M.A. Croft, A. Glasser, J.P. McDonald, R.J. James, G.A. Heatley, P.L. Kaufman; Accommodative Movements of the Ciliary Body (CB) and Lens in the Rhesus Monkey . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3889.
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To further elucidate how ciliary body movements effect lens function during accommodation and how this changes with age in rhesus monkeys, and to compare CB movements in phakic vs aphakic eyes.
Accommodation was stimulated via the Edinger–Westphal (E–W) nucleus in 26 rhesus monkeys, aged 6–24 yr, and the refractive change measured by coincidence refractometry. Centripetal ciliary body (CCB) and lens movements were measured by computerized image analysis of goniovideographic images. Ultrasound biomicroscopy (UBM) at 50 and 35 MHz was used to visualize accommodative movements of ciliary body and lens surfaces. Forward ciliary body (FCB) movement was measured as previously described.[Croft et. al. IOVS 2006]. CCB, lens and FCB movement at ∼3 diopters accommodation was examined in relation to age. The maximum attainable FCB movement was measured before and after extracapsular lens extraction (ECLE) or intracapsular lens extraction (ICLE).
The amount of centripetal lens movement required to induce ∼3 diopters of accommodation did not change with age (p= 0.5). The amount of CCB movement required to induce ∼3 diopters of accommodation increased significantly (slope= 0.0089±0.0032mm/yr; p=0.01) while the amount of FCB movement required declined significantly (slope= –1.4±0.25°/yr; p= 0.001) with age. The maximum amount of accommodative FCB movement measured tended to decrease following ICLE but not ECLE.
The eye may be attempting to compensate for the age–related loss of FCB movement by increased amounts of CCB movement to achieve a given level of zonular relaxation and a given level of accommodation. There appear to be differences in the age effect on FCB vs CCB movement. Stiffening of the posterior attachments of the ciliary muscle with age may have more effect on FCB than on CCB movement. The presence of the capsule and anterior zonule may play a role in FCB movement.
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