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M. A. Croft, J. P. McDonald, P. L. Kaufman; Age Related Changes of the Posterior Zonule and the Ciliary Body at Rest and During Accommodation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4028.
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Our goal was to determine the age-related changes in the function of the posterior zonule and the anatomical relationship of the posterior zonule to the other relevant intraocular accommodative structures.
The eyes of nineteen rhesus monkeys, aged 6-27 yrs, were studied. Edinger-Westphal- (E-W) stimulated accommodation was measured by coincidence refractometry. The width of the posterior zonular space and the distance from the scleral spur to the posterior insertion point of the posterior zonule was measured by ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz).
In the resting eye, the width of the posterior zonular space increased with age by 0.012 ± 0.0022 mm/yr (p=0.001, r=0.79, n=19), but the distance between the scleral spur and the posterior insertion point of the posterior zonule did not significantly change with age (n=3 young , n=3 older). During accommodation, the distance between the scleral spur and the posterior insertion point of the posterior zonule diminished (p<0.05) and did so more markedly in the young eyes (0.90 ± 0.09mm, n=3) than in the older eyes (0.43 ± 0.16mm, n=3), with no overlap. Further analyses are proceeding.
Age-related changes in ciliary body function may be secondary to the age-related loss in accommodative forward movement of the posterior zonule’s posterior insertion site. The age-related increase in posterior zonular space in the resting eye may be due to the decrease in the diameter of the ciliary body ring, which suspends the anterior end of the posterior zonule.
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