What is Which is the most common type of congenital cataract causing visual impairment and explain in detail?
CONGENITAL AND DEVELOPMENTAL CATARACT Lamellar cataract : Lamellar or Zonular cataract refer to the developmental cataract in which the opacity occupies a discrete zone in the lens. It is the most common type of congenital cataract presenting with visual impairment. Etiology: It may be either genetic or environmental in origin. a)Genetic pattern is usually of dominant variety. b)Environmental form is associated with deficiency of vitamin D. c) Sometimes maternal rubella infection contracted between 7th and 8th week of gestation may also cause lamellar cataract. Characteristic features: Typically, this cataract occurs in a zone of foetal nucleus surrounding the embryonic nucleus. The main mass of the lens internal and external to the zone of cataract is clear, except for small linear opacities like spokes of a wheel (riders) which may be seen towards the equator. It is usually bilateral and frequently causes severe visual defects. Ref:- A K Khurana; pg num:-172