The ultimate goal of cataract surgery, besides the restoration of distance visual acuity, is the res-toration of accommodation. Lens refilling with an injectable polymer has the potential of restoring accommodation following cataract surgery. Two main difficulties have hampered the success of lens refilling strategies in the past. First was leakage of the injectable material from the capsular bag and second was after-cataract formation resulting in loss of elasticity and pacification of the lens–bag complex. Recently, simplified and highly reproducible lens refilling procedures have been introduced with a potential for clinical application to restore accommodation.

Modern small incision cataract surgery with intraocular lens (IOL) implantation results in good visual acuity with an acceptably low risk for complications. However, the ultimate goal of modern cataract surgery also entails the elimination of the need for spectacles for near and distance by preserving accommodation in prepress biopic patients and restoring it in the presbyopia age group. This goal remains elusive. Lens capsular refilling with an injectable material in the presence of capsular and zonular integrity ancillary muscle function is an exciting and attractive prospect to restore ocular accommodation following lens surgery. Despite repeated experimental studies and modifications to capsular bag refilling techniques, several is-sues persistently plague investigators and prevent surgeons from achieving the ultimate clinical goal of restoring accommodation. The first is the leakage of injectable materials from the anterior capsule opening through which the lens matter was removed. The second is after-cataract in the form of fibrotic and regeneratory capsule pacification, which compromises elasticity of the capsule and visual acuity and, there-fore, accommodative function and optical clarity. The third is the titration of refractive power to achieve emmetropia as well as effective accommodation with-out induced optical aberrations and poor visual quality. Last but not least, the question remains if the residual ciliary muscle contractile force in aging eyes is enough to afford sufficient accommodative function with the available polymers. This review article presents an overview of the cur-rent knowledge about lens refilling techniques and their effect on accommodation and capsular bag transparency as well as the issues that remain to be resolved before they can become clinically applicable.

Elasticity of the Lens

Several investigations have been undertaken to measure lens elasticity.  The values were found to be similar to those measured with dynamic mechanical analysis on human lenses and further investigations to determine the correlation between age and lens elasticity and to quantify the contribution of the nucleus, cortex, and capsule to the modulus of elasticity are still to be done. The pending results should permit greater understanding of the roles of each component and aid in the development of lens refilling techniques.

CAPSULE TRANSPARENCY, STABILITY, AND AFTER-CATARACT PREVENTION

Capsule elasticity and transparency are mandatory for a successful outcome after lens refilling. After-cataract has been one of the main obstacles to lens re-filling as a procedure to treat presbyopia. Following cataract surgery, lens epithelial cells (LECs) profiler-ate and cause after-cataract in 2 ways: fibrotic and regeneratory after-cataract. The former results mainly in the loss of elasticity of the capsule due to lay down of collagen by myofibroblasts and the latter in compromised visual function due to in homogeneities caused by Elschnig pearls. Both components of after-cataract play a critical role with lens refilling. We are using the term after-cataract instead of posterior capsule pacification (PCO), as the latter term, even though often used synonymously, actually describes only changes on the posterior capsule. In modern cataract surgery, fibrotic after-cataract rarely causes clinical problems and regeneratory after cataract can be treated using neodymium: YAG capsulotomy. However, in the case of lens-refilling, fibrotic after-cataract can severely compromise accommodative function due to a decrease in capsule elasticity and regeneratory after-cataract may be difficult or impossible to treat due to the risk for leakage of refilling material into the posterior segment. This has made after-cataract the main hurdle to be tackled to achieve successful lens refilling. Therefore, the eradication or modulation of LECs is important for after-cataract prevention or control for lens refilling. In standard cataract surgery, the introduction of IOLs with a sharp optic edge has resulted in a significant decrease in PCO rates, probably due to contact inhibition at the capsule bend created by the optic edge. However, other factors such as IOL optic material and overall design of the IOL also influence PCO development, the regeneratory component of PCO with Elschnig pearls has been shown to undergo changes over relatively short periods of time, with an average life-span of pearls ranging from only a few weeks to several months.

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