Overview of Congenital, Senile and Metabolic Cataract

The lens is avascular biconvex ellipsoid transparent tissue, present in front of the anterior chamber of the eye; just behind the cornea. It is an ectodermal organ, developed at the 25th day of gestation. By the second month of intra-uterine growth, the spherical criteria structure of the lens is developed with characteristic anterior and posterior pole and dorsally outlined by lens epithelium. The lens fibers developed and matured after birth with subsequent formation of crystalline protein especially in adult state [1] The cornea is affected by continues light exposure which may be reflected in the structure of the lens with age. The lens comprises three main regions; capsule, lens epithelium, and lens fibers. The capsule is made up of dense connective tissue. The lens epithelium; lined the surface and it comprises a simple cuboidal epithelium. It possesses a vital function by regulating the homeostatic functions allowing the permeability of ions, nutrients, and osmolarity to the aqueous humor. It develops earlier during utero life in the 5th-6th week of gestation and maintains its normal integrity throughout [2]. The entire body of the lens is composed of concentric layers of tightly backed lens fibers interdigitated with each other by a ball and socket. Glucose represents the primary energy source of the lens tissues [3]. Sodium/potassium adenosine triphosphatase and calcium adenosine triphosphatase promote the osmolarity of the lens fibers [4]. Damage of the lens fibres lead to the formation of clouding in the lens and scattering of light, the predictor of cataract. It increases with age with a prevalence of about 50% in over 80 years old individuals [5]. There are different forms of cataracts; namely congenital [6] agerelated cataract [7] and metabolic cataract [8].