Many eye disorders are minor, but some can lead to serious complications without treated.
Congenital Defects
Squint (malalignment of the eyes) is sometimes congenital (present at birth). Cataracts (opacity of the lens) can occur in infants when the cause may be a maternal rubella infection early in pregnancy. Very rarely, babies are born with microphthalmos (abnormally small eye) on one or both sides. Vision in a microphtalmic eye is usually very poor. Nystagmus (uncontrollable movement in the eyes) is often congenital. Retinoblastoma is a malignant tumor of the retina that appears in early life and may occur in one or both eyes. Other congenital disorders affecting the eye include albinism (absence of pigment) and abnormalities of development of the cornea and retina.
Infection
Conjunctivitis , the most common infection, rarely affects vision. In the late stages of neglected conjunctival infection, such as trachoma or severe bacterial conjunctivitis, vision can be impaired. Corneal infections are more serious and can lead to blurred vision or corneal perforation if not treated early. Endophtalmitis (infection within the eye), which may make it necessary to remove the eye surgically, can occur after a penetrating injury, after severe ulceration, (rarely after major eye surgery, or from infections elsewhere in the body.
Impaired Blood Supply
Narrowing, blockage, pollution, or other abnormalities of the blood vessels of the retina may cause partial or total loss of vision.
Tumors
Malignant melanoma of the choroid (the layer of tissue between the retina and the sclera, which is the fibrous outer wall of the eyeball) is the most common primary malignant eye tumor. It can be found without symptoms during routine examinations or can cause a decrease in vision.
Nutritional Disorders
Various vitamin deficiencies (particularly vitamin A deficiency) can affect the eye. This may lead to xerophthalmia (dryness of the cornea and conjunctiva), night blindness, or keratomalacia (corneal softening and destruction).
Autoimmune Disorders
Uveities (inflammation of the uveal tissues-iris, choroid, or ciliary body), when not caused by an infectious agent may have an autoimmune basis. it is common in people with ankylosing spondylitis and sarcoidosis
Degeneration
Macular degeneration of the retina is common in the elderly. It causes loss of fine, detailed vision, although peripheral vision remains. Cataract is also common in the elderly; the exact cause is unknown.
Other Disorders
Glaucoma , is a condition which the pressure in the fluid maintaining the normal shape of the eye is raised, may take various forms. If untreated, glaucoma can lead to permanent loss of vision. In retinal detachment, the retina lifts away from the underlying (choroidal) layer of the eye.