Sclera

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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. 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.

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.

Additional images

References

External links

• - "Sagittal Section Through the Eyeball"

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Last updated on Wednesday February 27, 2008 at 19:00:19 PST (GMT -0800)
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