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 articleToxic optic neuropathy is a type of damage to the optic nerve that happens because a poison, a harmful drug, or a severe lack of key...
Read articleToxic Anterior Segment Syndrome—usually shortened to TASS—is a sudden, sterile (non-infectious) inflammation inside the front part of the eye after eye surgery, most commonly after cataract...
Read articleTownes-Brocks syndrome (TBS) is a rare, inherited condition that affects how several parts of the body form before birth. Doctors most often recognize TBS by a...
Read articleTorpedo maculopathy is a rare, usually harmless birth-time change in the eye’s retinal pigment epithelium (RPE)—the thin support layer under the seeing cells in the back...
Read articleTopical anesthetic abuse keratopathy is a serious injury to the clear front window of the eye (the cornea) that happens when a person uses numbing eye...
Read articleTolosa–Hunt Syndrome is a rare cause of severe eye pain with weak or frozen eye movements. Doctors call this “painful ophthalmoplegia.” In most people it affects...
Read articleGraves orbitopathy (also called thyroid eye disease) is an autoimmune eye condition that happens most often in people who have an overactive thyroid due to Graves...
Read articleTobacco optic neuropathy is a problem of the optic nerve that happens in people who use tobacco for a long time. The optic nerve is the...
Read articleTNF-alpha related optic neuropathy means damage to the optic nerve that is linked in some way to the tumor necrosis factor-alpha (TNF-α) pathway. In real life,...
Read articleTilted Disc Syndrome (TDS) is a harmless eye shape difference that a person is born with. It affects the way the optic disc looks. The optic...
Read articleThyroid Eye Disease (also called Graves’ orbitopathy or thyroid-associated ophthalmopathy) is an autoimmune condition where the body’s defense system mistakenly attacks the tissues around the eyes....
Read articleThygeson Superficial Punctate Keratitis—often shortened to TSPK—is a long-lasting, on-and-off inflammation of the front, clear window of the eye called the cornea. In TSPK, small, slightly...
Read articleCyclovertical muscle palsy is a problem with the eye muscles that move the eye up and down (vertical movement) and also twist the eye a little...
Read articleThiel–Behnke corneal dystrophy, sometimes called “honeycomb dystrophy” or corneal dystrophy of Bowman layer, type II (CDB2), is an inherited condition that affects the clear front window...
Read articleCorneal hysteresis is a biomechanical property of the cornea. The cornea is the clear, dome-shaped front window of the eye. Biomechanical means “how a living tissue...
Read articleCentral corneal thickness (CCT) is the exact thickness of the clear front window of your eye—the cornea—measured at its very center. It is usually written in...
Read articleTerson syndrome means bleeding inside the eye that happens together with bleeding inside the head or a very sudden rise in the pressure inside the skull....
Read articleTerrien’s marginal degeneration is a rare disease of the cornea, which is the clear front window of the eye. In Terrien’s disease, the outer edge (periphery)...
Read articleA temporary keratoprosthesis is a special, short-term, artificial cornea that a surgeon uses during complex eye surgery when the real cornea is too cloudy to see...
Read articleTemporal artery amyloidosis means “amyloid” protein has been laid down in the wall of the superficial temporal artery (the vessel your doctor sometimes biopsies when giant...
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