Polymer refilling of presbyopic human lenses in vitro restores the ability to undergo accommodative changes.

Abstract

Because presbyopia is thought to be accompanied by increased lens sclerosis this study was conducted to investigate whether refilling the capsule of the presbyopic human lens with a soft polymer would restore the ability of the lens to undergo accommodative changes. Accommodative forces were applied to natural and refilled lenses by circumferential stretching through the ciliary body and zonular complex. Nine natural lenses and 10 refilled lenses from donors ranging in age from 17 to 60 years were studied. Two refill polymers with a different Young's modulus were used. The lens power was measured by a scanning laser ray-tracing technique, and lens diameter and lens thickness were measured simultaneously while the tension on the zonules was increased stepwise by outward pull on the ciliary body. In the natural lenses the older lenses were not able to undergo power changes with stretching of the ciliary body, whereas in the refilled lenses, all lenses showed power changes comparable to young, natural lenses. The refilled human lenses had a higher lens power than the age-matched natural lenses. The Young's modulus of the polymers influenced the lens power change when measured with the ciliary body diameter increased by 4 mm. Refilling presbyopic lenses with a soft polymer enabled restoration of lens power changes with mechanical stretching. Because sclerosis of the lens is an important factor in human presbyopia, refilling the lens during lens surgery for cataract could enable restoration of clear vision and accommodation in human presbyopia.