OPHTHALMOLOGY AND RESEARCH

A Review of Lens Biomechanical Contributions to Presbyopia

Purpose: Presbyopia-the progressive loss of near focus with age-is primarily a result of changes in lens biomechanics. In particular, the shape of the ocular lens in the absence of zonular tension changes significantly throughout adulthood. Contributors to this change in shape are changes in lens biomechanical properties, continuous volumetric growth lens, and possibly remodeling of the lens capsule. Knowledge in this area is growing rapidly, so the purpose of this mini-review was to summarize and synthesize these gains.Methods: We review the recent literature in this field.Results: The mechanisms governing age-related changes in biomechanical properties remains unknown. We have recently shown that lens growth may be driven by zonular tension. The same mechanobiological mechanism driving lens growth may also lead to remodeling of the capsule, though this remains to be demonstrated.Conclusions: This mini-review focuses on identifying mechanisms which cause these age-related changes, suggesting future work which may elucidate these mechanisms, and briefly discusses ongoing efforts to develop a non-surgical approach for therapeutic management of presbyopia. We also propose a simple model linking lens growth and biomechanical properties.

A simple view of age-related changes in the shape of the lens of the human eye

Data describing the radius of curvature of the anterior surface of the human lens have been re-examined for (i) far-accommodated lenses and (ii) near-accommodated or excised lenses. It is found that, with increasing age, the curvatures converge to an intermediate value. Taking this together with the body of work on the mechanics of accommodative lens changes, a perspective is suggested which affords a simple view of curvature changes with age. The only datum in the literature is found to fit reasonably well with this perspective.