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 articleMyelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD) is an autoimmune disease of the central nervous system. “Autoimmune” means the immune system makes a mistake and attacks the...
Read articlePediatric low vision means a child cannot see well enough to do normal daily activities even when they use the best glasses or contact lenses that...
Read articleKeratoconus is an eye condition where the clear front window of the eye (the cornea) slowly becomes thinner and changes shape. Instead of being smoothly curved...
Read articlePattern strabismus means the eye misalignment is not the same in all up-and-down positions of gaze. In plain words, the amount of turning in or turning...
Read articlePattern dystrophies are inherited eye conditions that affect the retinal pigment epithelium (RPE) — the thin support layer under your light-sensing cells (photoreceptors). In these conditions,...
Read articlePaton’s lines are small, curved lines that you can see around the edge of the optic disc when the optic disc is swollen. The optic disc...
Read articleMyopic degeneration means the eye has become so long from front to back that the delicate tissues at the back of the eye start to stretch,...
Read articlePosterior staphyloma is a bulging “out-pouching” of the back wall of the eye because the white coat of the eye (the sclera) becomes thin and stretches,...
Read articlePathologic myopia is short-sightedness that has gone beyond just needing stronger glasses. In this condition, the back part of the eye (the retina, the layer that...
Read articleThe pars plana is a smooth, flat ring of tissue that sits just behind the colored part of the eye (the iris) and just in front...
Read articleParry–Romberg syndrome is a rare condition where one side of the face slowly becomes thinner and smaller over time. The thinning usually starts with the fat...
Read articleParkinson’s disease is a brain condition where special nerve cells that make a chemical called dopamine slowly die in a deep area of the brain called...
Read articleParinaud syndrome (also called dorsal midbrain syndrome) is a brain problem that affects how the eyes move and how the pupils react to light. It happens...
Read articleParinaud Oculoglandular Syndrome (often shortened to POGS) is an eye infection that usually affects just one eye. It causes a special kind of conjunctivitis (pink eye)...
Read articleParadoxical air embolism happens when tiny air bubbles that normally enter the veins (the “return” side of your circulation) find an abnormal shortcut to the arteries...
Read articleParacentral Acute Middle Maculopathy, or PAMM, is a problem in the middle layer of the retina (the light-sensing tissue at the back of the eye). On...
Read articlePapillorenal Syndrome (PRS) (also called Renal-Coloboma Syndrome or PAX2-related disorder) is a rare genetic condition that mainly affects the kidneys and the eyes. Most people with...
Read articlePapillophlebitis is a rare eye problem where the optic nerve head looks swollen and the retinal veins look big and twisty, usually in one eye of...
Read articlePapilledema means swelling of the optic nerve head (the “optic disc”) because the pressure inside the skull is too high. It’s not a disease by itself;...
Read articlePanuveitis is a kind of eye inflammation. It means the whole uvea is inflamed. The uvea is the “middle coat” of the eye. It has three...
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