A physical model demonstrating Schachar's hypothesis of accommodation.

Schachar's hypothesis of accommodation states that there is increased zonular tension during accommodation and the observed in vivo changes in lenticular curvature that occur during accommodation are the result of zonular forces. To demonstrate that there can be steepening of the central curvature of the lens with increased zonular tension, profile photographs of an equatorially unstretched and stretched gelatin-filled balloon and profile photographs from the literature of an unstretched and equatorially stretched human lens were digitized. Their radii of curvature were determined. We found that equatorial stretching of both the gelatin-filled balloon and the human lens produced central curvature steepening that was consistent with Schachar's hypothesis of accommodation.