Cataract and cataract surgical coverage

The human lens is an optically clear structure that lies between the iris and the vitreous body of the eye. It is transparent, biconvex, composed of lens fibers, and surrounded by capsule. The lens is supported by zonules on either side. The nucleus of the lens is made up of older lens fibers, while newer fibers are located in the cortex at the outer layers of the lens. Cortical cataracts may develop within the anterior or posterior cortex of the lens, and often do not cause visual symptoms unless the visual axis is affected. Posterior sub-capsular cataracts occur mainly in the central posterior aspect of the posterior cortex of the lens and can develop rapidly. Cataracts can be secondary to ocular or systemic diseases, such as diabetes, which causes a two- to five-fold increased risk of developing lens opacity. The aetiology of age-related cataracts is multifactorial. Older age is associated with increasing prevalence of nuclear and cortical cataracts.