Recurrent corneal erosion (RCE) is a condition where the very top layer of the clear window at the front of your eye—the corneal epithelium—keeps loosening and ...

Rebound iritis means the inflammation in the front part of the eye (the iris and the fluid just behind the cornea) comes back soon after it looked like it was ...

Raymond Syndrome is a rare stroke syndrome that happens when a small area in the front-middle part of the pons (a section of the brainstem) is damaged—most ...

A Rathke cleft cyst is a small, fluid-filled pocket that forms in the area of the pituitary gland at the base of the brain. It sits in a bony space called the ...

Paratrigeminal oculosympathetic syndrome is a rare condition where two things happen on the same side of the face and head. First, the sympathetic nerve supply ...

Paratrigeminal syndrome is a rare pain condition that affects one side of the face and the eye. It causes deep, constant pain around the eye and forehead, and ...

Raeder syndrome (also called Raeder paratrigeminal syndrome or paratrigeminal oculosympathetic syndrome) is a rare nerve problem on one side of the head and ...

Radiation retinopathy is damage to the light-sensitive layer at the back of the eye (the retina) that happens months to years after radiation treatment to the ...

Radiation optic neuropathy is damage to the optic nerve and the nearby visual pathway that happens after a person receives radiation to the head, brain, eye, ...

Pythium keratitis is a serious infection of the clear front window of the eye (the cornea) caused by a water-loving germ called Pythium insidiosum. This germ ...

Pyogenic granuloma is a non-cancerous growth made of many tiny blood vessels packed together.The name is confusing because it is not caused by pus and not a ...

Pyoderma gangrenosum is a rare skin disease where the body’s immune system attacks the skin by mistake and creates very painful open sores called ulcers. These ...

Purtscher retinopathy is a sudden eye condition where tiny blood vessels in the retina (the light-sensing layer at the back of the eye) become blocked and the ...

Polychromatic Pre-Descemet’s Corneal Dystrophy is a rare, inherited change in the clear front window of the eye called the cornea. In this condition, tiny ...

Punctiform Pre-Descemet’s Corneal Dystrophy is a rare corneal condition in which tiny dot-like, often multicolored (“polychromatic”) specks collect deep inside ...

Punctate inner choroidopathy, often shortened to PIC, is an eye condition that affects the choroid and the outer layers of the retina. The choroid is the thin ...

Punctal stenosis means the small tear drain opening on the eyelid margin (called the punctum) becomes too narrow or nearly closed. Every eye has two puncta—one ...

Punctal atresia (also called punctal agenesis) means the tiny tear-duct opening at the eyelid margin—the lacrimal punctum—never formed or is completely sealed ...

The Pulfrich phenomenon is a special kind of depth illusion that happens when the two eyes send their motion signals to the brain at slightly different speeds. ...

Pterygium is a triangular, wing-shaped piece of tissue that grows from the clear white part of the eye (the conjunctiva) onto the clear front window of the eye ...