A saccade is a very fast eye movement that jumps your line of sight from one spot to another spot. Your eyes do not slide smoothly during a saccade. They ...

A ruptured globe is a full-thickness tear of the wall of the eye after a strong blunt blow. The eye has a tough outer coat made of the clear cornea in the ...

Rowland Payne Syndrome is a neuro-anatomical triad—three problems that usually happen on the same side of the neck and chest—caused by a single area of damage ...

Roth spots are small bleeds inside the retina—the light-sensitive tissue at the back of the eye—with a pale or white center in the middle of the bleed. The ...

Ross syndrome is a rare disorder of the autonomic nervous system (the automatic nerves that control sweating, pupil size, and reflexes). Doctors recognize it ...

Rosai–Dorfman disease (RDD)—also called sinus histiocytosis with massive lymphadenopathy—is a rare disorder where a specific type of immune cell called a ...

Rho-kinase inhibitor–associated corneal epithelial edema is a temporary swelling of the surface layer (epithelium) of the cornea that appears after using ...

Rhinosporidiosis is a long-lasting infection that mainly grows on moist lining tissues of the nose, throat, and eyes. It is caused by a microscopic organism ...

Rhino-orbital-cerebral mucormycosis, often shortened to ROCM, is a very serious fungal infection that usually starts in the nose and the sinuses, then can ...

Rhabdomyosarcoma (RMS) is a cancer that starts from cells that are supposed to become skeletal muscle. Skeletal muscle is the muscle that moves our arms, legs, ...

Reversible Posterior Leukoencephalopathy Syndrome is a sudden brain problem that usually gets better when the cause is treated. Doctors also call it Posterior ...

A relative afferent pupillary defect (RAPD) is a difference in how the two eyes send light signals to the brain. In a normal system, shining a light in either ...

Reversal of Vision Metamorphopsia means a person suddenly sees the whole world turned completely upside down, as if the entire scene has been rotated by 180 ...

Retrobulbar hemorrhage means blood collects in the tight space behind the eyeball inside the bony eye socket. The eye socket is like a closed box that does not ...

Retinopathy of prematurity, or ROP, is an eye disease that happens in some babies who are born too early and too small. The retina is the light-sensing layer ...

Retinoblastoma is a cancer that starts in the retina, which is the thin light-sensing layer at the back of the eye. The tumor grows from very early retinal ...

Retinitis pigmentosa is a group of inherited eye conditions that slowly damage the retina, which is the thin, light-sensing tissue that lines the inside of the ...

Retinal vein occlusion is a blood-flow problem inside the eye. The retina is a thin, light-sensing layer at the back of the eye that turns light into signals ...

Retinal vasculitis means there is inflammation in the tiny blood vessels inside the retina, which is the light-sensitive layer at the back of the eye. When ...

An RPE tear is a sudden rip in the thin brown “support layer” under the retina called the retinal pigment epithelium (RPE). This layer normally sits flat on a ...