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 articleOrbital fat prolapse is a bulge of normal eye socket fat that slowly slips forward through a thin natural curtain in the eyelid called the orbital...
Read articleOrbital emphysema means air gets trapped in the soft tissues around the eye (the “orbit”). The orbit is a bony cup that holds the eye, muscles,...
Read articleOrbital compartment syndrome is a true eye emergency. It happens when pressure inside the eye socket (the orbit) rises quickly and gets so high that blood...
Read articleOrbital cellulitis is a serious infection that happens behind the eye, inside the bony eye socket called the orbit. The orbit is a tight space filled...
Read articleA cavernous hemangioma (also called a cavernous venous malformation in many body parts, and a cerebral cavernous malformation [CCM] when it is in the brain or...
Read articleAn orbital cavernous venous malformation is a benign (non-cancerous) blood-vessel problem inside the bony eye socket (the orbit). It is made of smooth, low-flow venous channels...
Read articleOrbital aspergillosis is a fungal infection around or inside the eye socket. The eye socket is also called the orbit. The orbit has the eyeball, the...
Read articleOrbital Apex Syndrome is a problem that happens in a very tight space at the very back of the eye socket, called the orbital apex. This...
Read articleOrbital adipose tissue disease” isn’t a formal diagnosis. It’s a descriptive way to say “the fat inside the eye socket is part of the disease.” In...
Read articleOrbital actinomycosis is a long-standing bacterial infection that grows in and around the eye socket (the orbit). The orbit is the bony cup that holds the...
Read articleThe ora serrata is the serrated junction where the retina (the light-sensitive tissue at the back of the eye) transitions into the ciliary body. It marks the anterior...
Read articleOptociliary shunt vessels are special “detour” blood vessels that appear on the surface of the optic disc, which is the round, pink area where the optic...
Read articleAn optic disc pit is a small, round or oval congenital hole or pocket in the optic nerve head. The optic nerve head is the spot...
Read articleAn optic pit is a tiny, oval or round depression (a small “dimple”) on the surface of the optic nerve head—the place where the nerve exits...
Read articleOptic perineuritis (often shortened to OPN) is an inflammation that sits around the optic nerve, not inside the nerve itself. The optic nerve is the cable...
Read articleCraniofacial fibrous dysplasia is a bone problem that happens in the skull and face. In this condition, normal hard bone is slowly replaced by soft, rubbery,...
Read articleMcCune-Albright syndrome (MAS), some people develop fibrous dysplasia (FD) in the skull and face bones. FD is a bone problem where normal bone is replaced by...
Read articleOptic neuropathy means there is damage or disease affecting the optic nerve, the cable that carries visual signals from the eye to the brain. When the...
Read articleOptic neuritis means inflammation of the optic nerve, the “cable” that carries pictures from your eye to your brain. When this nerve gets inflamed, vision drops—often...
Read articleOptic nerve sheath meningioma is a slow-growing, usually benign (non-cancerous) tumor that starts in the thin lining (the meninges) that wraps around the optic nerve. The...
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