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

1. 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.

4. 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.

5. 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

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

7. 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

8. 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.

9. 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.

10. 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.

11. Nerve supply of the sclera
 The sclera is supplied by the branches from the long
ciliary nerves anteriorly and short ciliary nerves
behind the equator.

12. Function

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