Browse plain-English disease and condition guides, including symptoms, causes, diagnosis, treatment options, prevention, and when to seek medical care.
Persistent Hyperplastic Primary Vitreous (PHPV)—now more often called Persistent Fetal Vasculature (PFV) is a congenital (present at birth) eye condition. In a developing baby, the eye has...
Read articleAblepharon-Macrostomia Syndrome (AMS) is an extremely rare, autosomal dominant genetic disorder characterized principally by absent or underdeveloped eyelids (“ablepharon”) and an unusually wide, fish-like mouth (“macrostomia”)...
Read articleAcanthamoeba keratitis is a rare but potentially sight-threatening corneal infection caused by the free-living amoeba Acanthamoeba, which is found ubiquitously in soil, fresh water, and even...
Read articleAccommodative esotropia is a common form of childhood strabismus in which one or both eyes turn inward (esodeviation) because of excessive focusing (accommodation) linked to farsightedness...
Read articleAchromatopsia is a rare eye condition that affects how a person sees color. People with achromatopsia typically have trouble seeing colors or can only see them...
Read articleAchromatopsia is a rare, inherited vision disorder that causes a complete or partial inability to see color. People with achromatopsia rely almost entirely on their rod...
Read articleAchromatopsia 2 (ACHM2) is a genetic eye condition that starts from birth. It mainly affects the cone cells in the retina, which are the light-sensing cells...
Read articleAcquired Developmental Prosopagnosia, often referred to as ADP, is a condition that affects a person’s ability to recognize faces. It’s a complex condition, and in this...
Read articleAcquired ectropion uveae (AEU) is a condition in which the pigmented posterior layer of the iris—normally hidden on the back surface—becomes adherent to and everts onto...
Read articleAcquired oculomotor nerve palsy is a non-congenital condition in which the third cranial nerve (oculomotor nerve) becomes damaged after birth, leading to dysfunction of most extraocular...
Read articleAcquired ophthalmoparesis is a condition characterized by weakness or paralysis of one or more extraocular muscles—those that control eye movements—due to processes that occur after birth....
Read articleAcquired Orbital Dysmorphia (AOD) is a medical condition that affects the structure and appearance of the eye socket and surrounding areas. In simpler terms, it means...
Read articleRetinal artery occlusion is a sudden blockage of the blood vessel that brings oxygen-rich blood to the retina. The retina is the thin, light-sensitive layer at...
Read articleRetinal Angiomatous Proliferation (RAP) is a special pattern of “wet” age-related macular degeneration (AMD). In RAP, tiny new blood vessels start inside the retina itself (not...
Read articleReticular Subretinal Drusenoid Deposits are tiny, spot-like or net-like buildups of material that sit above the retinal pigment epithelium (RPE) in the subretinal space, right under...
Read articleReticular pseudodrusen (often shortened to RPD) are tiny, grain-like deposits that sit above the retinal pigment epithelium (RPE) in the outer retina, in the zone where...
Read articleReticular drusen are tiny, yellow-white bumps that sit above the retinal pigment epithelium (RPE), in the shallow space just under the light-sensing cells. Doctors also call...
Read articleA corneal foreign body means that something that does not belong in the eye gets stuck on, or inside, the clear front window of the eye...
Read articleRelentless placoid chorioretinitis is a rare eye inflammation that affects the layer under the retina (the choroid and the retinal pigment epithelium). Doctors also call it...
Read articleA relative afferent pupillary defect means the pupils do not react equally when a light is moved from one eye to the other. Doctors check this...
Read articleRefractive error is a problem where the eye does not focus light exactly on the retina, so the picture you see is not perfectly sharp, and...
Read articleRecurrent 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...
Read articleRebound 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...
Read articleRaymond 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...
Read articleA 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...
Read articleParatrigeminal oculosympathetic syndrome is a rare condition where two things happen on the same side of the face and head. First, the sympathetic nerve supply to...
Read articleParatrigeminal 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...
Read articleRaeder syndrome (also called Raeder paratrigeminal syndrome or paratrigeminal oculosympathetic syndrome) is a rare nerve problem on one side of the head and face. Raeder syndrome...
Read articleRadiation 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...
Read articleRadiation 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,...
Read articlePythium 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...
Read articlePyogenic 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...
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