Presbyopia, accommodation, and the mature catenary

Objective. To demonstrate a plausible explanation of aging changes and to r educe the controversy relative to accommodation by using a mechanical model of the catenary theory of lens change. Mechanical Modeling: A mechanical model was used to simulate a human lens i n both the accommodated and unaccommodated state to demonstrate changes in the mechanism of accommodation with age. Methods: Fluid-filled latex balloons were supported by a plastic wrap hammo ck to form a catenary that models the human lens. Increasing volumes were u sed to simulate that of the aging lens, and variations in curvature were me asured. Main Outcome Measures. The degree of curvature of a simulated anterior lens surface was measured and compared with mathematical modeling of its optica l surface based on the catenary hydraulic suspension theory. Results: The measurements showed that accommodative loss and other features such as mass displacement, reproducible lens surfaces, and zonule support are consistent with the catenary theory of accommodation and an increasing lens volume with age. Conclusions: The catenary theory of accommodation provides a basis for eval uating age changes of the human lens. Variable results with surgical proced ures for presbyopia are also predictable with the model. These results can be used to provide a basis for intraocular lens design. (C) 2001 by the Ame rican Academy of Ophthalmology.