From Wikipedia, the free encyclopedia
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.[1] It is derived from the neural crest[2]. 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.
Limbus is the border between cornea and sclera
It borders with the cornea by the corneal limbus.
[edit] Histology
From outer to innermost, the three layers of the sclera are:
- Episclera
- Stroma
- Lamina fusca
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.
[edit] Additional images
Interior of anterior half of bulb of eye.
|
The terminal portion of the optic nerve and its entrance into the eyeball, in horizontal section.
|
The interior of the posterior half of the left eyeball.
|
[edit] References
- ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainesville, Florida: Triad Publishing Company, 1990.
- ^ Hermann D. Schubert. Anatomy of the Orbit http://www.nyee.edu/pdf/schubert.pdf
[edit] External links
