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M. A. Croft, J. P. McDonald, P. L. Kaufman; Configuration of the Ciliary Body: Accommodation and Presbyopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5790.
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Our goal was to determine the age-related changes in ciliary body configuration at rest and during accommodative movements.
Coincidence refractometry was used to measure accommodation induced by electrical stimulation of the Edinger-Westphal (E-W) nucleus in the rhesus monkey. The lens, ciliary body thickness in the region of the pars plana, and the arc of the inner aspect of the ciliary body were measured by ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz). The eyes of 11 rhesus monkeys, aged 5-28 yrs, were studied. Analogous UBM images were collected in human patients (ages 59-60 yrs) to compare ciliary body configuration and zonular attachments in relation to the monkey eyes.
The arc of the inner aspect of the resting ciliary body decreased with age in the monkey eyes, and the thickness of the ciliary body in the region of the pars plana decreased significantly with age by 0.008 ± 0.003mm/yr (n=10; p=0.025); averaging 0.38 ± 0.015 mm (n=5) in the young eyes and 0.26 ± 0.03 mm in the older eyes (n=4). The ability of the monkey eye to accommodate was significantly related increased resting muscle width (39.5 ± 16.5 diopters/mm muscle width; p=0.043; n=11). We are currently collecting analogous images and measurements across the age spectrum in human subjects. The images thus far collected in the human eye (n=2) clearly show the ciliary body, the vitreous zonule and that measurements can be taken in the human eye analogous to the monkey eye.
The age-related decrease in width of the ciliary body in the region of the pars plana may have an effect on the vitreous zonule tension and may affect lens shape and thereby accommodation. The presence of the vitreous zonule in the human eye raises the possibility that this could be a biological target, the disruption of which could be used to restore forward muscle movement as demonstrated previously in the monkey eye. These findings may provide some insight into successful accommodating IOL design.
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