The stiffness of human cataract lenses is a function of both age and the type of cataract.

Surgical evidence suggests that nuclear cataract lenses are generally harder than normal lenses. We examined this quantitatively using dynamic mechanical analysis of cataract lenses removed during surgery and compared the results with data from normal lenses. Stiffness of the lens centre was found to depend on the type of cataract and the age of the patient. Nuclear cataract lenses were generally stiffer than those extracted from patients with predominantly cortical cataract, with some in the latter group appearing not to differ significantly from age-matched normals. At age 40-50, the nuclear region of advanced nuclear cataract lenses was found to be approximately 46 times harder than that of normal lenses of the same age. By age 70-80 the stiffness of advanced nuclear cataract lenses had doubled, however, by this age, normal lenses had also increased significantly in stiffness so that the difference between cataract and normal lenses was much less pronounced, being a factor of approximately 2.5.