Common causes of<unk> s include demyelinating disease such as multiple sclerosis (retrobulbar neuritis), damage to nerve fiber layer in the retina (seen as cotton wool spots) due to hypertension, toxic substances such as methyl alcohol, ethambutol and quinine, nutritional deficiencies, vascular blockages either in the retina or in the optic nerve, stroke or other brain injury, and macular degeneration, often associated with aging. Scintillating<unk>  is a common visual aura in migraine. Less common, but important because they are sometimes reversible or curable by surgery, are<unk> ta due to tumors such as those arising from the pituitary gland, which may compress the optic nerve or interfere with its blood supply. Rarely,<unk> ta are bilateral. One important variety of bilateral<unk>  may occur when a pituitary tumour begins to compress the optic chiasm (as distinct from a single optic nerve) and produces a bitemporal paracentral<unk> , and later, when the tumor enlarges, the<unk> s extend out to the periphery to cause the characteristic bitemporal hemianopsia. This type of visual-field defect tends to be obvious to the person experiencing it but often evades early objective diagnosis, as it is more difficult to detect by cursory clinical examination than the classical or textbook bitemporal peripheral hemianopia and may even elude sophisticated electronic modes of visual-field assessment. In a pregnant woman,<unk> ta can present as a symptom of severe preeclampsia, a form of pregnancy-induced hypertension. Similarly,<unk> ta may develop as a result of the increased intracranial pressure that occurs in malignant hypertension. The<unk>  is also caused by the aminoglycoside antibiotics mainly by streptomycin.
Scotoma
Tar melanosis
Apudoma
Cementoma
Ocular melanosis
Bowenoid papulosis
Melasma
Erythrasma