4 - LENS AND GLAUCOMA

Abstract

A cataract is opacity in the clear lens. Normally, the human lens converge light rays. Opacity in the lens will scatter or block the light rays. If the opacity is small and at the lens periphery, there is little or no interference with vision. On the other hand, when the opacity is central and dense, the light rays can be severely interfered with. This will lead to blurred vision. The most common cause of cataract is old age, and this is known as senile cataract. The surgical removal of cataract is by the intracapsular or extracapsular method. In intracapsular cataract extraction, the whole lens together with its capsule is removed. In extracapsular extraction, the nucleus and the cortex are removed through an opening in the anterior capsule leaving the posterior capsule intact. In the normal eye, there is a delicate balance between the inflow and outflow of aqueous. When the outflow is blocked, the intraocular pressure rises, leading to optic nerve damage. This condition is known as glaucoma. There are two main types of glaucoma: (1) open-angle glaucoma, which develops insidiously and leads to visual loss with few or no symptoms, and (2) closed-angle glaucoma, which develops suddenly and is associated with acute pain, sudden visual loss, and congestion of the eye.