Cataract is a condition of the crystalline lens which leads to its (crystaline len's) opacification. The crystalline lense is an avascular and transparent structure which consists of the lens capsule, the lens epithelium, the lens fibre- the nucleus and the peripheral cortex. The crystalline lens is situated behind the iris but lies anterior to the vitreous chamber and the retina.
The lens capsule is the thin, transparent hyaline membrane that surrounds the crystalline lens. It is rich in elastins and collagen. It also contains phospholipids in the form of glycosaminoglycans, a substance the provides connective tissue-like reinforcement to the lens capsule. The cilliary body attaches zonules projecting from the lens capsule known as suspensory ligaments.
The lens epithelium is a basal membrane that is situated in the anterior portion of the lens. It is made up of single layer of cubiodal cells with active mitosis taking place throughout life. The older lens fibre produced are pushed to the middle where it forms the nucleus and the outer surface forms the peripheral cortex. The lens fibre, it should be noted, consists of the main mass of the lens material. The fibres are formed by the multiplication and differentiation of the lens epithelial cells. The posterior portion of the lens has no epithelium.
The crystalline lens is composed of chiefly of crystallins. Crystallins are transparent proteins that gives the crystallines its transparency including the parallel arrengement of lens cell materials. Crystallins commonly found in the human is alpha-, beta- & gamma-crystallins and it composes of about 90% of the total lens protein. The crystalline lens is bathed anteriorly by the more active aqueous humor, while the less active vitreous humor bathes posterior aspect of the crystalline lens. Any loss of transperency of the lens results to cataract.
Cataract causes functional blindness to the individual.
To be continued...
Dr Ezebuiroh Victor Okwudiri.
