OCULAR STRUCTURES
Posted by recep on April 19th, 2009Conjunctiva
The conjunctiva is the thin mucous membrane covering the sclera. Its goblet cells produce mucin, essential for lubricating eyelid movement and providing a protective layer to slow evaporation of the tear film. With aging, the number of mucous cells decreases, either as a result of keratitis sicca (with or without Sjogren’s syndrome) or non-specifically. These changes contribute to dry eye syndrome, manifested by a scratchy sensation and chronic irritation, often with increased redness from conjunctival vascular dilation (see also Lacrimal Gland and Tear Drainage, below). Diagnosis is confirmed by examining the cornea with slit-lamp biomicroscopy, and treatment usually consists of methylcellulose eyedrops (artificial tears) or a variation of them.
The conjunctiva can also undergo metaplasia and hyperplasia. This may lead to tissue accumulation at the nasal or temporal junction of the sclera and cornea, called a Pinguecula. Connective tissue that grows, vascularizes, and invades the cornea is called a pterygium (see FIG. 102-2). If a pterygium continues to grow and reaches the center of the cornea, it can interfere with vision. Pterygia usually occur in people who spend a lot of time outdoors, especially in dusty and windy environments. Frequently occurring in women, Pingueculae may be a cosmetic problem, but they rarely require removal; however, pterygia should be followed, and at first evidence of corneal involvement, surgical excision should be considered.
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