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 [skle´rah] (L.)
the tough, white outer coat of the eyeball, covering approximately the posterior five-sixths of its surface, continuous anteriorly with the cornea and posteriorly with the external sheath of the optic nerve. adj., adj scle´ral.
The sclera and other eye structures. From Lammon et al., 1995.
blue sclera abnormal blueness of the sclera; it is a prominent feature of osteogenesis imperfecta and is also seen in certain other conditions. (See Atlas 1, Part B.)
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


, pl.




(sklē'ră, -ăz, -ē), [TA]
A portion of the fibrous layer forming the outer envelope of the eyeball, except for its anterior sixth, which is the cornea.
[Mod. L. fr. G. sklēros, hard]
Farlex Partner Medical Dictionary © Farlex 2012


The tough white fibrous outer envelope of tissue covering all of the eyeball except the cornea. Also called sclerotic, sclerotic coat.

scle′ral adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


, pl. scleras, pl. sclerae (skleră, -ăz, -ē) [TA]
A portion of the fibrous tunic forming the outer envelope of the eye, except for its anterior one sixth, which is the cornea.
Synonym(s): sclerotica.
[Mod. L. fr. G. sklēros, hard]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


The white of the eye. The tough outer coating of dense, interwoven collagen fibrils visible through the transparent overlying CONJUNCTIVA.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005




the outer coat of the vertebrate eye to which are attached extrinsic muscles for moving the eyeball. The sclera is lined by a vascular layer, the CHOROID, except for the forward-facing part which is called the CORNEA and is transparent, with no underlying choroid.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


The tough, fibrous, white outer protective covering that surrounds the eye.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


The tough, white, opaque, fibrous outer tunic of the eyeball covering most of its surface (the cornea contributes 7% of, and completes, the outer tunic). Its anterior portion is visible and constitutes the 'white' of the eye. In childhood (or in pathological conditions) when the sclera is thin, it appears bluish, while in old age it may become yellowish, due to a deposition of fat. The sclera is thickest posteriorly (about 1 mm) and gradually becomes thinner towards the front of the eyeball. It is a sieve-like membrane at the lamina cribrosa. The sclera is pierced by three sets of apertures: (1) the posterior apertures round the optic nerve and through which pass the long and short posterior ciliary vessels and nerves; (2) the middle apertures, 4 mm behind the equator which give exit to the vortex veins; and (3) the anterior apertures through which pass the anterior ciliary vessels. The tendons of insertion of the extraocular muscles run into the sclera as parallel fibres and then spread out in a fan-shaped manner. The sclera is commonly considered to be divided into three layers from without inward: (1) the episclera, (2) the scleral stroma and (3) the suprachoroid (lamina fusca) which is interposed between choroid and sclera. Syn. sclerotic. Note: some authors consider the suprachoroid as belonging to the choroid. However, when choroid and sclera are separated part of the suprachoroid adheres to the choroid and part to the sclera. See cribriform plate; evisceration.
blue sclera A hereditary defect in which the sclera has a bluish appearance. The sclera is thinner than normal and is susceptible to rupture if the person engages in contact sports. It is often associated with fragility of the bones and deafness as part of a condition called osteogenesis imperfecta (fragilitas ossium, van der Hoeve's syndrome), with keratoconus or with acquired scleral thinning (e. g. necrotizing scleritis). Syn. blue sclerotic (Fig. S3). See Ehlers-Danlos syndrome; Marfan's syndrome.
Fig. S3 Blue scleraenlarge picture
Fig. S3 Blue sclera
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann


, pl. scleras, pl. sclerae (skleră, -ăz, -ē) [TA]
Portion of fibrous layer forming outer envelope of eyeball, except for its anterior sixth, which is the cornea.
[Mod. L. fr. G. sklēros, hard]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about sclera

Q. My 11 y/o son eyes appear to have a slight yellow in the whites toward the corners. I am assuming he will need blood work, but does anyone have any idea what may be the cause?

A. If it's not a spot, but rather a diffuse color, it may be jaundice - high levels in the blood of a substance called bilirubin (

If your child is generally healthy, and this change appeared without any overt problem (e.g. liver disease or blood problem), or your child had fever or fasted recently, this jaundice may represents Gilbert syndrome. It's a syndrome of slightly elevated levels of bilirubin, and considered not dangerous.

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References in periodicals archive ?
The importance of this work, in relation to the tissues used, lies in minimizing alterations in the transparency of the cornea and the physical properties of the sclera that occur with age, but the use of inhibitors would also be expected to minimize the detrimental effects of glycation in other collagen-containing tissues.
A modified technique of sclera fixated intra ocular lenses for aphakic correction.
Functional results of posteriorchamber lens implantation with sclera fixation.