What we know and understand about presbyopia

Abstract

The major theories for presbyopia are reviewed. These date from the very earliest hypotheses to current ideas and encompass both rheological (mechanical or elastic) and optical factors. Experimental findings are presented to support or refute the theories. The onset and rate of progression of presbyopia is shown to have multifactorial influences and a substantial contribution comes from an age-related change in the refractive index gradient of the lens cortex. (Clin Exp Optom 1993; 76: 3: 83–90)