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 articlePyoderma gangrenosum is a rare skin disease where the body’s immune system attacks the skin by mistake and creates very painful open sores called ulcers. These...
Read articlePurtscher retinopathy is a sudden eye condition where tiny blood vessels in the retina (the light-sensing layer at the back of the eye) become blocked and...
Read articlePolychromatic Pre-Descemet’s Corneal Dystrophy is a rare, inherited change in the clear front window of the eye called the cornea. In this condition, tiny spots of...
Read articlePunctiform Pre-Descemet’s Corneal Dystrophy is a rare corneal condition in which tiny dot-like, often multicolored (“polychromatic”) specks collect deep inside the cornea, just in front of...
Read articlePunctate inner choroidopathy, often shortened to PIC, is an eye condition that affects the choroid and the outer layers of the retina. The choroid is the...
Read articlePunctal stenosis means the small tear drain opening on the eyelid margin (called the punctum) becomes too narrow or nearly closed. Every eye has two puncta—one...
Read articlePunctal atresia (also called punctal agenesis) means the tiny tear-duct opening at the eyelid margin—the lacrimal punctum—never formed or is completely sealed over. Because the opening...
Read articleThe Pulfrich phenomenon is a special kind of depth illusion that happens when the two eyes send their motion signals to the brain at slightly different...
Read articlePterygium is a triangular, wing-shaped piece of tissue that grows from the clear white part of the eye (the conjunctiva) onto the clear front window of...
Read articlePseudoxanthoma elasticum (PXE) is a rare, inherited condition that slowly changes the body’s elastic tissues. “Elastic tissues” are stretchy parts that help the skin, the back...
Read articlePseudotumor cerebri means the pressure inside the skull is higher than normal even though there is no brain tumor. The word “pseudo” means “false,” so the...
Read articlePseudostrabismus means the eyes only look misaligned, but they are actually straight. The word “pseudo” means “false.” The word “strabismus” means “true eye misalignment.” In pseudostrabismus,...
Read articleIrvine–Gass Syndrome is swelling in the center of the retina (the macula) that happens after cataract surgery. The swelling forms many tiny fluid-filled spaces shaped like...
Read articlePseudophakic cystoid macular edema is swelling in the very center of the retina (the macula) that happens after cataract surgery. “Pseudophakic” means there is an artificial...
Read articlePseudophakic bullous keratopathy is a long name that describes a clear problem in very simple terms, and the plain meaning helps you understand it step by...
Read articleAphakia means the eye has no natural lens. The lens is normally a clear structure that focuses light. Aphakia can happen because the lens was removed...
Read article“Pseudophakic” means the natural lens of the eye has been removed (usually because of cataract) and replaced with an artificial lens implant, called an intraocular lens...
Read articlePseudopapilledema means the optic nerve head (the “disc” you see at the back of the eye) looks swollen, but it is not truly swollen from raised...
Read articlePseudomonas keratitis is a serious infection of the cornea—the clear, dome-shaped window at the front of the eye—caused by a bacterium called Pseudomonas aeruginosa. This germ...
Read articlePseudoexfoliative glaucoma is a type of glaucoma that happens because tiny, flaky fibers build up in the front part of the eye. These fibers are not...
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