sclera n : whitish fibrous membrane (albuginea) that with the cornea forms the outer covering of the eyeball [syn: sclerotic coat]

English

Pronunciation

• Rhymes: -ɪərə

Noun

sclera (plural scleras or sclerae)

1. The white of the eye. It is the tough outer coat of the eye that covers the eyeball except for the cornea.

Synonyms

• sclerotic
• sclerotic coat

Derived terms

• scleral
• scleritis

Translations

• Finnish: silmänvalkuainen
• Polish: twardówka

The sclera, called the white or white of the eye, is the opaque (usually white, though certain animals, such as horses and lizards, can have black sclera), fibrous, protective, outer layer of the eye containing collagen and elastic fibers. It is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, however, fatty deposits on the sclera can make it appear slightly yellow.

The sclera forms the posterior five sixths of the connective tissue coat of the globe. It is continuous with the dura mater, and maintains the shape of the globe, offering resistance to internal and external forces, and provides an attachment for the extraocular muscle insertions. The thickness of the sclera varies from 1mm at the posterior pole to 0.3 mm just behind the rectus muscle insertions. The main parts of the eye also include the conjunctiva. This is a thin layer covering the sclera.

It borders with the cornea by the corneal limbus.

Histology

From outer to innermost, the three layers of the sclera are:

• Episclera
• Stroma
• Lamina fusca

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To avoid confusion, the cornea, which is an outer continuation from the sclera, has 5 layers. The middle, thickest layer is also called the stroma. Lazic surgery to correct vision is usually done in this region of the cornea. THE CORNEA IS LOCANTED INSIDE THE EYEBALL.

Additional images

References

External links

• - "Sagittal Section Through the Eyeball"