corneal transparency

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CORNEAL TRANSPARENCY

CORNEAL TRANSPARENCY

JAYADEVI.A

Primary physiological functions of the cornea is to maintain its transparency and protect the intraocular contents

Cornea consists of three layers epithelium stroma endothelium

Factors determining transparencyPeculiar arrangement of corneal lamellae

Avascularity

Relative state of dehydration

Metabolism of cornea

Higher difference between refractive index of cornea and air

STROMA

Transparency of cornea is related to the regularity of stromal componentsStroma is composed of type1 collagen fibers set in ground substance of mucopolysaccharidesThis ribbon like bundle formation gives the laminated appearanceCollagen fibers are spaced equidistantly and form the hexogonal lattice

LATTICE THEORYLattice formation leads to interfibrillar spacing of less than the wave length of light. so that tangential rows of fibers acts as a diffraction grating resulting in destructive interference of scattered rays

GOLDMAN AND BENEDEK THEORYIt is based on dimension of refractive elements in corneal stroma.There is least scattering of light till spatial dimension of variations in refractive index remains