Opaque fibrous outer layer of the eyeball[ZFA,Kardong,WP]. [ http://en.wikipedia.org/wiki/Sclera http://zfin.org/ZDB-PUB-050701-15 ]

This is just here as a test because I lose it

Term information

database cross reference

uberon_slim, pheno_slim, vertebrate_core


Disease notes: implicated in rheumatoid arthritis.

depicted by


development notes

Seko et al demonstrate chondrogenic potential and identify this as connective tissue[DOI:10.1371/journal.pone.0003709].

Majority derives from NC that surrounds optic cup of neurectoderm; a small temporal portion develops from the mesoderm that contributes to striated extra-ocular muscles and vascular endothelia[Rada&Johnson].

external definition

The sclera, also known as the white part 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 fiber. 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 the cornea, and maintains the shape of the globe, offering resistance to internal and external forces, and provides an attachment for the extraocular muscle insertions. The sclera is perforated by plenty of nerves and vessels passing through the posterior scleral foramen, the hole that is formed by the optic nerve. At the optic disk the outer two-thirds of the sclera continues with the dura mater (outer coat of the brain) via the dural sheath of the optic nerve. The inner third joins with some choroidal tissue to form a plate (lamina cribrosa) across the optic nerve with perforations through which the optic fibers (fasciculi). The thickness of the sclera varies from 1mm at the posterior pole to 0.3 mm just behind the rectus muscle insertions. The sclera's blood vessels are mainly on the surface, and together with the conjunctiva (which lies on top) This is a thin layer covering the sclera. Along with the vessels of the conjunctiva, those of the sclera renders the inflamed eye bright red. [WP,unvetted][Wikipedia:Sclera].

The tough, usually white, outer coat of the eyeball, covering all the posterior surface and continuous anteriorly with the cornea. [TFD][VHOG]

has related synonym

scleral capsule



structure notes

continuous with the dura mater and the cornea; The sclera forms the posterior five-sixths of the connective tissue coat of the globe.

taxon notes

in fish, reptiles and monotremes the connective tissue of the sclera is skeletal