An optic disc melanocytoma (ODM) is a small, very dark brown or black growth made of pigment cells (melanocytes) that sits on the optic disc (the “entrance” of ...

An optic disc hemorrhage is a small spot of bleeding on or next to the optic disc. The optic disc is the place in the back of the eye where the optic nerve ...

Optic disc drusen are tiny, hard, pebble-like deposits that sit inside the “head” of the optic nerve where it enters the back of the eye (the optic disc). They ...

Optic atrophy means the optic nerve is damaged and has lost healthy fibers, so the nerve cannot carry visual messages from the eye to the brain as well as it ...

Opsoclonus-Myoclonus Syndrome (OMS)—also called opsoclonus-myoclonus-ataxia syndrome (OMAS) or Kinsbourne syndrome. Opsoclonus-Myoclonus Syndrome (OMS) is a ...

Recurrent Painful Ophthalmoplegic Neuropathy (RPON) is a rare condition in which a person has two or more attacks of a unilateral (one-sided) headache together ...

Ophthalmomyiasis means fly larvae (maggots) invade the eye or the tissues around the eye. It is uncommon, but it can harm vision if it is not treated quickly. ...

Rift Valley fever (RVF) is a viral disease that mainly affects animals (like sheep, goats, cattle, camels, and buffalo) but can also infect people. It is ...

Leptospirosis is an infection caused by spiral-shaped bacteria called Leptospira. These bacteria live in the kidneys of many animals and come out in their ...

Kyasanur Forest Disease (KFD) is a viral hemorrhagic fever that people get after a bite from an infected tick in or near forested areas. The virus belongs to ...

Thrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening blood disorder. Tiny clots form inside many of the body’s smallest blood vessels. These ...

Spinocerebellar ataxia (SCA) is a large family of inherited brain disorders in which the cerebellum—the brain’s “coordination center”—and its connections ...

Obstructive sleep apnea is a sleep disorder where your throat repeatedly narrows or closes while you sleep. Air has trouble getting into your lungs. This ...

Facioscapulohumeral dystrophy (FSHD) is a genetic muscle disease. The name tells you which muscles are hit first: the face (facio-), the shoulder blades ...

Creutzfeldt-Jakob disease (CJD) is a rare, fast-moving, and always fatal brain disorder. It happens when a normal body protein called prion protein changes ...

MELAS stands for Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes. It is a rare genetic condition that affects how the tiny “power ...

Fatal Familial Insomnia (FFI) is an ultra-rare, inherited prion disease. A single change in the PRNP gene (classically D178N with methionine at codon 129) ...

Tuberous sclerosis complex (TSC) is a genetic condition in which harmless-looking overgrowths of tissue (called hamartomas) can develop in many organs. The ...

Sinus pericranii (SP) is a rare problem with veins in the skull. In SP, there is an unusual “shortcut” vein that connects veins inside the skull (the dural ...

Ophthalmic Manifestations of SIBO (Small Intestinal Bacterial Overgrowth) means there are too many bacteria in the small intestine. Those bacteria can ...