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 articleTrichiasis means the eyelashes grow or point the wrong way and touch the eye surface. In simple words, the lashes that should point outward toward the...
Read articleTriangle symbol on the eye is almost always a pterygium (pronounced tuh-RIJ-ee-um): a triangular, wing-shaped, fleshy growth that starts on the white part of the eye...
Read articleTrematode-Induced Uveitis (TIU) is eye inflammation caused by trematodes, which are parasitic flatworms (“flukes”). In certain regions, especially in rural areas where people—often children—swim or bathe...
Read articleTreacher–Collins syndrome (TCS) is a genetic condition that mainly affects how the bones and soft tissues of the face grow before birth. The first and second...
Read articleTraumatic Optic Neuropathy means damage to the optic nerve—the cable that carries visual signals from the eye to the brain—caused by injury. The injury can be...
Read articleA traumatic motor neuropathy is an injury to a nerve that primarily carries motor signals—the messages that tell muscles to contract—caused by some form of trauma....
Read articleA traumatic macular hole is a small, round opening that goes through the full thickness of the central retina (the macula) after an injury to the...
Read articleTraumatic lens dislocation means the natural lens of the eye has been knocked out of its normal position by an injury. The lens is a clear,...
Read articleTraumatic iritis means inflammation inside the front of the eye (mainly the colored ring called the iris, and sometimes the nearby ciliary body) after an injury....
Read articleTraumatic Horner Syndrome happens when the “fight-or-flight” nerve supply to one eye and the same side of the face is interrupted somewhere along a long three-step...
Read articleTraumatic globe luxation means the eyeball is pushed or pulled out of its normal place in the bony eye socket after a force or injury. In...
Read articleTraumatic glaucoma is high pressure inside the eye that happens after an eye injury. The injury can be a strong hit to the eye, a cut...
Read articleA traumatic cataract is a clouding of the eye’s natural lens that starts after an injury to the eye. The lens sits just behind the colored...
Read articleSmartphone Vision Syndrome is a group of symptoms that start or get worse during or after long smartphone use. It happens because our eyes, eyelids, and...
Read article“Smartphone blindness” is a popular phrase people use when they suddenly notice poor vision after looking at a phone. In most cases, it is not true,...
Read articleTransient smartphone blindness means a short-lasting loss or dimming of vision that happens after looking at a smartphone, most often while lying in bed in the...
Read articleTrachoma is an eye infection caused by a tiny bacterium called Chlamydia trachomatis. Repeated infections over many years make the inside of the eyelids rough and...
Read articleTraboulsi syndrome is a very rare, inherited eye condition in which several things tend to happen together. People often have a distinct facial appearance (usually flat...
Read articleToxoplasmosis is an infection caused by a tiny parasite called Toxoplasma gondii. This parasite lives in many warm-blooded animals, but cats are the main animals that...
Read articleToxocariasis is an infection caused by the roundworms Toxocara canis (from dogs) and Toxocara cati (from cats). People get sick after swallowing the microscopic eggs of...
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