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 articleFundus flavimaculatus is an eye condition that slowly harms central vision. It usually starts in childhood, the teenage years, or young adult life, but it can...
Read articleStaphyloma is an eye condition where part of the outer layer of the eyeball (called the sclera or cornea) becomes stretched, thinned, and bulges outward. This...
Read articleSquamous carcinoma of the eyelid is a skin cancer that starts in the squamous cells. These are the flat cells on the surface of the skin...
Read articleSpontaneous intracranial hypotension means the pressure of the fluid that bathes your brain and spinal cord—the cerebrospinal fluid (CSF)—falls lower than it should without a recent...
Read articleSpheroidal degeneration is a slow, wear-and-tear change on the clear front window of the eye called the cornea. In this condition, tiny round droplets made mostly...
Read articleSpasmus nutans is a rare eye movement problem that usually begins in early infancy. It has three main features. The first feature is very fast, very...
Read articleSpasm of the Near Synkinetic Reflex is a condition where the eyes act as if they are always looking at something very close, even when the...
Read articleSpaceflight-Associated Neuro-Ocular Syndrome, or SANS, is a set of eye and optic nerve changes that can develop during long space missions. In simple terms, the body’s...
Read articleSorsby macular dystrophy is a rare, inherited eye disease that damages the macula, which is the central part of the retina that you use for sharp,...
Read articleA solitary fibrous tumor (SFT) is a lump that grows from supporting (connective) tissue cells. These cells make fibers such as collagen, so the tumor often...
Read articleSolar retinopathy is an eye injury that happens when very strong light from the sun enters the eye and hurts the most sensitive part of the...
Read articleSoemmering’s ring is a circular build-up of leftover lens cells and lens material that forms around the rim of the natural lens capsule after cataract surgery...
Read articleSlit Ventricle Syndrome (SVS) is a problem that can happen in people who have a brain shunt for hydrocephalus. A shunt is a thin tube that...
Read articleSkew deviation is a vertical eye misalignment that comes from a problem in the balance system in the brain. One eye sits higher and the other...
Read articleSinusitis-induced optic neuropathy means the optic nerve is damaged because of disease in the nearby sinuses. The optic nerve is the cable that carries visual signals...
Read articleA simultaneous bilateral cataract means both lenses of your eyes become cloudy at the same time or close to the same time. The lens is the...
Read articleSimultanagnosia is a problem with visual attention. A person can see one thing at a time, but cannot see the “whole picture” when many things appear...
Read articleLimbal epithelial disease means there is a problem in the thin, living skin-like layer that covers the front window of the eye near the edge where...
Read articleSilicone oil keratopathy means damage and disease of the clear front window of the eye, called the cornea, that happens after silicone oil is used inside...
Read articleSilent Sinus Syndrome (SSS) happens when one maxillary sinus (the air space under your eye) slowly collapses inward because its natural drainage/airflow pathway is blocked. Air...
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