Eye, disorders of

Many eye disorders are minor, but some can cause loss of vision unless treated. (See also cornea, disorders of; retinal detachment.) Squint is sometimes present at birth. Rarely, babies are born with microphthalmos. Other congenital disorders that affect the eye are nystagmus, albinism, and developmental abnormalities of the cornea and retina. Conjunctivitis is the most common eye infection and rarely affects vision. Trachoma or severe bacterial conjunctivitis can impair vision. Corneal infections can lead to blurred vision or corneal perforation if not treated early. Endophthalmitis (infection within the eye) can occur as a result of eye injury or infection elsewhere in the body. Narrowing, blockage or inflammation of the blood vessels of the retina may cause partial or total loss of vision. Malignant melanoma of the choroid is the most common cancerous tumour of the eye. Retinoblastoma is a cancerous tumour of the retina that most commonly affects children. Various vitamin deficiencies (particularly of vitamin A) can affect the eye. This may lead to xerophthalmia, night blindness, or, ultimately, keratomalacia. Uveitis may be caused by infection or an autoimmune disorder such as ankylosing spondylitis and sarcoidosis. Macular degeneration of the retina is common in the elderly, as is cataract. Glaucoma, in which the pressure inside the eyeball becomes raised, can lead to permanent loss of vision. In retinal detachment, the retina lifts away from the underlying layer of the eye. Ametropia is a general term for any focusing error, such as astigmatism, myopia, or hypermetropia. Presbyopia is the progressive loss with age of the ability to focus at close range. Amblyopia is often due to squint.