Development of lens

Embyology

1. DEVELOPMENT OF LENS Y.SAI GOUTHAM REDDY ROLL NO 176

2. Embr y ology  Development of eye starts around day 22 of gestation .  At this stage, embryo has 8 pairs of somites and around 2mm in length. Formation of optic vesicle  Neural plate shows linear thickened area on either side of it.  It depresses to form the optic sulcus .  It then forms the optic vesicle .  Proximal part of optic vesicle constricts & elongate to form the optic stalk.

3. Formation of lens vesicle  At around 27 day of gestation, area of surface ectoderm overlying optic vesicle thickens, called as lens placode.  It sinks gradually to form the lens vesicle .  It gets s e p e rated from t he surfa c e e c tod e rm by 3 3 rd day of gestation.

4.  Lens vesicle is lined by single layer of cells covered by basal lamina.  Cells from the posterior wall of vesicle elongate rapidly to form the primary lens fibers .  Their base remain anchored to the basal lamina posteriorly and their apices grow towards the anterior lens epithelium.

5.  Primary lens fibres are formed up to the 3 rd month of gestation.  These fibres are preserved as the compact core of lens, called embryonic nucleus .  Hence, posterior aspect of the lens become devoid of epithelium.

6.  Equatorial cells of the anterior epithelium forms the secondar y l en s fibres .  Tips of the these fibres extend around the primary fibres and they meet at the Y-shaped anterior and posterior lens sutures.

7. THESE C A T ARACTS ARE PRESENT A T BI R TH OR TH A T DEVELO P WITHIN THE FIRST YEAR OF LI F E ARE CAL L ED CONGENI T AL /IN F ANTI L E C A T ARA C T . F AIR L Y OCCU R RIN G IN 1 OF EVE R Y 2 L I VE BI R THS - SOME LE N S O P ACITIES D O N OT PR O G R ESS AND ARE US U A L L Y INS I GNIFICANT - O T HE R S CA N PRODU C E PROF O U N D VISUAL IM P AIRMENT