Sclera

anatomy of eyes , ocular structure , sclera , choroid , retina ,eyeball, parts of eyes ,ocular anatomy, ocular physiology

1. SCLERA NETHRADHAMA SCHOOL OF OPTO

2. Introduction The sclera forms the posterior opaque 5/6 part of the external fibrous tunic of the eyeball. Its whole outer surface is covered by tenon’s capsule and also by the bulbar conjunctiva in the anterior part Its inner surface lies in contact with the choroid with a potential suprachoroidal space in bertween . Sclera is thickest posteriorly(1mm) and gradually becomes thin when traced anteriorly.

3. Special regions of sclera Scleral sulcus: It is an indentation(furrow) on the inner surface of the anterior most point of the sclera near the limbus . Sclera spur It is a circular flang of the anterior most part of the sclera which lie deep to schlemm’s canal. It appears wedge-shaped in section.

4. Special regions of sclera Lamina cribrosa : It is a sieve-like sclera from which the fibres of the optic nerve pass. Scleral apertures( emissaria ): Sclera has three sets of apertures : Posterior aperture : situated around the optic nerve. Middle apertures: situated 4-7mm posterior to the equator. Anterior aperture: situated 3-4mm away from the limbus

5. Microscopic structure Histologically, sclera consist of following three layers Epicleral tissue Sclera proper Lamina fusca

6. Microscopic structure Episcleral tissue It is a thin, dense vascularised layer of the connective tissue which covers the sclera proper. Anteriorly it becomes continuous with the tenon’s capsule

7. Microscopic structure Sclera proper It is an avascular structure which consist of dense bundles of collagens fibres crossing each other in all direction. This arrangement makes the sclera opaque in contrast to cornea Mucopolysaccharides are present in the interfibrillar space of the collagen fibre. Few fibroblasts are also present in this layer.

8. Microscopic structure Lamina fusca It is the innermost part of sclera which blends with suprachoroidal and supraciliary lamina of the uveal tract. It is brownish in colour owing to the presence of pigment cells.

9. Blood supply of the sclera The episclera receives its blood supply  from   the anterior ciliary arteries, anterior to   the   insertions   of   the   rectus muscles and the long and short posterior ciliary arteries.

10. Nerve supply of the sclera The sclera is supplied by the branches from the long ciliary nerves a nteriorly and short ciliary nerves behind the equator.

11. Function

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