Diseases of the Sclera

Diseases of the Sclera

Episcleritis

• Typically affects young adults, being twice as common in women than men.
• Etiology in most cases is not known. Occurs in association with gout, rosacea, psoriasis and as hypersensitivity reaction to endogenous tubercular or streptococcal proteins.
• Types: Diffuse episcleritis, nodular episcleritis.
• In nodular episcleritis, a pink or purple flat nodule surrounded by congestion is usually situated 2- 3 mm away from the limbus
• Episcleritis periodica refers to a fleeting type of disease.
• Treatment in severe cases is with topical steroids and systemic indomethacin 50 mg twice daily.

Diseases of the ScleraScleritis

• Usually occurs in elderly patients (40-70 years), involving females more than the males. More rare than episcleritis.
• About 50 percent cases are associated with some connective tissue disease.
• About 0.5 percent of patients with seropositive rheumatoid arthritis develop scleritis.
• Causes of non-pyogenic scleritis are syphilis, tuberculosis, and leprosy.
• In scleritis pain is moderate to severe, deep and boring in character.
• Classification
I. Anterior scleritis
– Non-necrotizing: diffused or nodular
– Necrotizing: with or without inflammation
II. Posterior scleritis
• Non-necrotizing anterior diffuse scleritis is the most common clinical variety.
• Scleromalacia perforans refers to anterior necrotizing scleritis without inflammation. It is common in women with long-standing seropositive rheumatoid arthritis. There is no effective treatment for this condition.
• Posterior scleritis is frequently misdiagnosed. Its features are proptosis, limitation of ocular movements, exudative retinal detachment, macular oedema.
• Comea and uveal tract are frequently involved in scleritis and not in episcleritis.

Blue sclera

• A typical association of osteogenesis imperfecta.
• Other associations are Marfan ’ s syndrome, Ehlers Danlos syndrome, pseudoxanthoma elasticum, congenital glaucomas, scleritis and Werner’s syndrome.

Staphyloma

• Bulging of the ectatic cicatricial outer coat of the eyeball lined by uveal tissue.
• Anterior staphyloma results after total sloughing of the comea.
• Intercalary staphyloma may occur after scleritis, perforating injury, peripheral comeal ulceration.
• Ciliary staphyloma may occur following scleritis, perforating injury or absolute glaucoma.
• Equatorial staphyloma commonly occurs at the regions of sclera which are perforated by vortex veins.
• Posterior staphyloma may occur due to pathological myopia (most common cause), posterior scleritis, posterior perforating injury.

Causes of scleral thinning

• Uveitis
• Scleritis
• Tuberculoma
• Congenital glaucoma

Miscellaneous points

• Diseases of the sclera are chronic because of relative avascularity of sclera.
• Sclera is thickest at the  posterior pole and thinnest at the lamina cribrosa.