Ophthalmic delusional parasitosis is a mental health condition where a person has a fixed, unshakable belief that parasites (like insects, worms, or mites) are ...

An ophthalmic artery pseudoaneurysm is a small, dangerous bulge that forms in the ophthalmic artery, the blood vessel that supplies the eye and the tissues ...

Ophthalmia nodosa is eye inflammation that happens when tiny hairs or spines from certain insects—most often caterpillars—or spiky plant fibers get into your ...

One-and-a-Half Syndrome is a special eye movement problem caused by a small injury in the brainstem (the “pons”). It knocks out almost all side-to-side eye ...

An oncocytoma is a tumor made of special cells called oncocytes. Oncocytes are cells that look pink and grainy under the microscope because they are packed ...

African River Blindness, also called onchocerciasis, is a long-lasting infection caused by a tiny worm named Onchocerca volvulus. People get it when blackflies ...

Onchocerciasis is a long-lasting infection caused by a tiny worm called Onchocerca volvulus. People get this worm when blackflies bite them many times over ...

Oculopharyngeal Muscular Dystrophy—usually shortened to OPMD—is a genetic muscle disease that mainly weakens the muscles of the eyelids (“oculo-”) and the ...

Oculopalatal tremor is a movement disorder where the eyes move back and forth in a smooth, slow, repetitive way, and the soft palate inside the mouth also ...

Oculomotor synkinesis is a problem where different eye and eyelid parts move together even when they should move separately. It happens because the third ...

Oculomotor apraxia (often shortened to OMA) is a problem with starting quick eye movements on purpose. These quick eye movements are called saccades. Saccades ...

Oculomotor apraxia (often shortened to OMA) is a problem with starting quick eye movements on purpose. These quick eye movements are called saccades. Saccades ...

Oculomasticatory myorhythmia is a very rare movement pattern where the eyes rock slowly back and forth while the jaw or facial chewing muscles contract in the ...

Oculogyric crisis is a sudden spell where both eyes pull up (most often) or to the side and seem “stuck” there for minutes to hours. It is a kind of ...

Oculodermal melanocytosis—also called Nevus of Ota—is a birth-related (congenital) pigment condition. Extra pigment cells sit deep in the skin and the white ...

Nevus of Ota is a birthmark made of extra pigment cells that sit deep inside the skin and sometimes inside the eye. The word “nevus” means a patch. “Ota” is ...