High myopia is a severe form of nearsightedness (myopia) in which distant objects appear very blurry while close objects remain clear. In technical terms, it ...
High altitude retinopathy (HAR) is an eye condition that arises when people ascend to high elevations—usually above 2,500 m (about 8,200 ft)—and experience low ...
Herpes Zoster Uveitis is an eye condition in which the varicella-zoster virus (VZV)—the same virus that causes chickenpox and shingles—reactivates and inflames ...
Herpes Zoster Optic Neuritis is a rare but serious inflammation of the optic nerve caused by reactivation of the varicella-zoster virus (VZV)—the same virus ...
Herpes Zoster Ophthalmicus (HZO) is a painful, viral infection of the eye and the surrounding skin, caused by the reactivation of the varicella-zoster virus ...
Herpes Simplex Virus (HSV) Stromal Endotheliitis is a type of eye inflammation caused by the herpes simplex virus affecting the deep layers of the cornea. In ...
Herpes Simplex Virus Stromal Keratitis (often shortened to HSV Stromal Keratitis) is a serious infection of the corneal stroma—the thick, transparent middle ...
Herpes Simplex Uveitis is a form of eye inflammation caused by infection with the herpes simplex virus (HSV). In plain English, “herpes simplex” refers to a ...
Herpes Simplex Epithelial Keratitis (HSEK) is an eye infection affecting the thin, clear front layer of the eye called the corneal epithelium. It is caused by ...
Hereditary Hyperferritinemia Cataract Syndrome (HHCS) is a rare, autosomal dominant genetic disorder characterized by persistently elevated serum L-ferritin ...
Hereditary Benign Intraepithelial Dyskeratosis (HBID) is a rare genetic disorder characterized by the development of white, plaque-like lesions on the surface ...
Hereditary Angiopathy with Nephropathy, Aneurysms, and Muscle Cramps (HANAC) syndrome is a rare genetic disorder caused by mutations in the COL4A1 gene. This ...
Hemorrhagic Occlusive Retinal Vasculitis (HORV) is a rare but serious inflammatory condition affecting the small blood vessels (vasculature) in the retina, the ...
Intraocular pressure is the pressure inside your eye. Think of your eye like a small, flexible ball filled with a clear fluid. That clear fluid in the front ...
Hemifacial spasm is a nervous system disorder characterized by involuntary, irregular muscle contractions on one side of the face. These spasms often begin ...
Hemangiopericytoma (HPC) is a rare vascular tumor that arises from pericytes—cells that wrap around small blood vessels. Recent studies classify it within the ...
Helicoid peripapillary chorioretinal degeneration (HPCD) is a rare, slowly progressive eye disorder characterized by a winding (“helicoid”) band of ...
Heimann–Bielschowsky Phenomenon (HBP) is a type of involuntary eye movement (nystagmus) that occurs in a single, non-seeing (blind) eye. Unlike more common ...
Heerfordt–Waldenström syndrome, also called uveoparotid fever, is a rare form of sarcoidosis. In this condition, tiny clumps of inflammatory cells called ...
Heavy Eye Syndrome (also known as myopic strabismus fixus or strabismus fixus convergence) is a form of acquired eye misalignment (strabismus) that occurs ...
Cerebrospinal fluid (CSF) lymphocytosis is a condition in which the number of lymphocytes— a type of white blood cell—in the fluid surrounding your brain and ...
Hashimoto encephalopathy (HE), also called steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a rare condition in which the ...
Harlequin syndrome is a rare nerve condition that causes one side of the face and sometimes the upper body to turn red and sweat while the other side remains ...
Harding’s disease, also known as Harding’s syndrome, is a rare overlap of Leber’s hereditary optic neuropathy (LHON) and a multiple sclerosis–like illness. ...
Hallucinogen Persisting Perception Disorder (HPPD) is a condition where people continue to see changes in vision long after taking a hallucinogenic drug. In ...
Hallermann–Streiff syndrome (HSS) is a very rare genetic disorder that affects the development of the skull, face, skin, hair, teeth, and eyes. People with HSS ...
Gyrate Atrophy of the Choroid and Retina is a rare, inherited eye disorder that causes progressive loss of vision. It is caused by a deficiency of the enzyme ...
Esophageal dysbiosis refers to an imbalance in the normal microbial community of the esophagus. Under healthy conditions, the esophageal mucosa hosts a diverse ...
Nasal dysbiosis happens when the tiny living creatures (microbes) that normally keep your nose healthy get out of balance. In very simple terms, your nose has ...
Urinary Dysbiosis refers to an imbalance in the naturally occurring microorganisms (the microbiome) within the urinary tract. For many years, urine was thought ...
Respiratory dysbiosis is an imbalance in the community of microorganisms that normally live in the airways and lungs. In a healthy respiratory tract, a diverse ...
Vaginal dysbiosis is a condition in which the natural balance of microorganisms in the vagina is disturbed, allowing harmful or opportunistic microbes to ...
Oral dysbiosis refers to an imbalance in the community of microorganisms (bacteria, fungi, viruses) that live in the mouth. In a healthy mouth, these microbes ...
Gut dysbiosis means that the tiny creatures living in your digestive tract—mostly bacteria, but also viruses and fungi—are out of balance. In a healthy gut, ...
Dysbiosis is when the balance of helpful and harmful microorganisms in your gut breaks down. Think of your digestive tract as a garden: you need more of the ...
Neuropsychiatric dysbiosis is a condition where the community of microorganisms living in your gut (the gut microbiota) becomes unbalanced, leading to problems ...
Metabolic dysbiosis refers to an imbalance in the body’s metabolic processes, often driven by disruptions in gut microbes, hormone signaling, or nutrient ...
Small Intestinal Bacterial Overgrowth, or SIBO, happens when too many bacteria—usually the kinds normally found in the colon—grow in the small intestine. Under ...
Functional dysbiosis is an imbalance in the normal functions of the gut microbiome. The gut microbiome is a diverse community of bacteria, viruses, fungi, and ...
Inflammatory dysbiosis is an imbalance in the community of microbes living in the gut—beneficial bacteria decline while harmful species flourish—triggering ...
Infectious dysbiosis refers to an imbalance in the body’s microbial communities—most often in the gut—triggered by the overgrowth of pathogenic organisms ...
Gut microbiome diseases are health conditions that happen when the tiny living creatures in your gut—bacteria, viruses, fungi, and other microbes—get out of ...
Granulomatosis with Polyangiitis (GPA), formerly known as Wegener’s Granulomatosis, is a rare autoimmune disease characterized by inflammation of small- to ...
Granular Corneal Dystrophy (GCD) is a rare, inherited eye condition in which small, breadcrumb-like deposits slowly build up in the middle layer (stroma) of ...
Gradenigo syndrome is a rare condition that happens when an infection in the middle ear (otitis media) spreads into the tip of the temporal bone called the ...
Gorlin–Goltz syndrome, also known as nevoid basal cell carcinoma syndrome, is a rare inherited condition that affects multiple parts of the body. It happens ...
Gorham–Stout disease (GSD), also called vanishing bone disease or phantom bone disease, is an extremely rare condition in which patches of bone slowly ...
Godtfredsen syndrome is a rare neurological condition characterized by the simultaneous impairment of the sixth cranial nerve (abducens nerve) and the twelfth ...
McArdle Disease (also called Glycogen Storage Disease Type V) is a rare inherited condition that affects how muscle cells use stored sugar (called glycogen) ...
Glycogen is your body’s “quick-use” sugar storage. Think of it like a rechargeable battery made of many glucose units. Your liver stores glycogen to keep blood ...
Posner–Schlossman Syndrome (PSS), also known as glaucomatocyclitic crisis, is a rare eye condition marked by sudden, temporary spikes in pressure inside one ...
Glaucomatocyclitic crisis, also called Posner–Schlossman syndrome (PSS), is a rare eye condition marked by sudden, short-lived rises in pressure inside one eye ...
Glaucoma is a group of eye conditions that damage the optic nerve, which carries visual signals from your eye to your brain. When this nerve is harmed, vision ...
Glaucoma refers to a group of eye conditions in which damage to the optic nerve leads to vision loss, often associated with high pressure inside the eye ...
Giant retinal tears (GRTs) are serious eye injuries that can lead to rapid vision loss if not recognized and treated promptly. In very simple English, a giant ...
Giant Fornix Syndrome (GFS) is a rare, long-lasting eye disease. In GFS, pus keeps coming from the eye because bacteria hide in a very deep fold (fornix) under ...
Giant cell arteritis is a serious condition in which the walls of medium- and large-sized arteries (the blood vessels carrying blood away from the heart) ...
Ghost cell glaucoma is a rare form of secondary open-angle glaucoma that happens when the fluid drainage system of the eye becomes blocked by small, rigid, ...
Gerstmann syndrome is a rare neurological condition first described in 1924 by Austrian neurologist Josef Gerstmann. It arises when a small region of the ...
Geographic atrophy (GA) is the advanced, late stage of the dry form of age-related macular degeneration (AMD). In GA, patches of light-sensing cells in the ...
Genetic eye diseases are conditions affecting vision that are caused by changes in our DNA. DNA is the blueprint for our bodies, and when certain parts of this ...
Gelatinous Drop-Like Corneal Dystrophy (GDLD) is a rare inherited eye disease. In this disorder, the clear front window of the eye (the cornea) develops soft, ...
Gaze-Evoked Amaurosis (GEA) is a rare eye condition in which a person temporarily loses vision in one eye when looking in a particular direction. The vision ...
Gardner syndrome is a rare inherited disorder now recognized as a variant of familial adenomatous polyposis (FAP). In this condition, dozens to thousands of ...
Galactokinase deficiency, also known as Type II galactosemia, is a rare genetic disorder in which the enzyme that normally converts galactose into ...
Fungal keratitis is an infection of the clear front window of the eye (the cornea) caused by a fungus. The cornea helps focus light onto the retina, allowing ...
Fungal endophthalmitis is an infection that affects the inside of the eye. In simple terms, it happens when tiny living organisms called fungi enter the clear ...
Fundus autofluorescence (FAF) is a non-invasive imaging modality that has become increasingly popular in both research and clinical settings due to its ability ...
Functional Visual Loss (FVL), also known as Nonorganic Visual Loss (NOVL), describes a genuine experience of reduced sight without any detectable damage or ...
Fulminant idiopathic intracranial hypertension (FIH) is a rare, rapidly progressive form of idiopathic intracranial hypertension (IIH). In IIH, cerebrospinal ...
Fuchs’ Endothelial Dystrophy is a condition of the cornea, the clear “window” at the front of the eye. In this disorder, the innermost layer of the ...
Fuchs’ Superficial Marginal Keratitis (FSMK) is a rare eye disease that affects the outer edge of the clear front window of the eye (the cornea). In FSMK, the ...
Fuchs heterochromic iridocyclitis (FHI) is a rare, chronic form of anterior uveitis—an inflammation of the front part of the eye—that most often affects only ...
A frontocutaneous fistula is an abnormal tunnel that runs from the frontal sinus (located behind your forehead) through bone and soft tissue to the skin ...
Froin syndrome is a rare neurological sign characterized by the triad of cerebrospinal fluid (CSF) xanthochromia (yellow discoloration), markedly elevated CSF ...
Friedreich ataxia is a rare inherited disease that damages parts of the nervous system and heart. It makes it hard to walk, harms muscle coordination, and can ...
Foville Syndrome is a rare brainstem condition caused by a lesion—usually in the dorsal (back) part of the pons in the brainstem—that damages certain nerve ...
The fovea is a tiny pit in the center of the retina (the back of the eye) that gives us very sharp central vision—what we use to read, recognize faces, and see ...
Foster-Kennedy Syndrome is a rare neurological and eye-related condition where one eye shows optic atrophy (a pale, shrunken optic nerve indicating ...
The Foldable Capsular Vitreous Body (FCVB) is a medical device made to replace the natural gel (the vitreous) inside the back part of the eye when that gel is ...
A focal scleral nodule is a small, round, benign lump that grows from the white outer coat of the eye called the sclera. It usually looks yellowish or white, ...
Focal Choroidal Excavation (FCE) is a small, deep pit or depression in the choroid layer of the eye that is seen most clearly with detailed imaging, especially ...
Floppy Eyelid Syndrome (FES) is an eye condition where the upper eyelid becomes too loose and stretchy. Because the eyelid is very soft and lax, it can flip ...
Fleck Corneal Dystrophy (FCD) is a rare inherited eye condition that affects the clear front part of the eye called the cornea, specifically the middle layer ...
Firework and shrapnel eye injuries are serious and can cause permanent loss of vision if not recognized and treated quickly. These injuries happen when ...
A firearm ocular injury means that a gun or projectile has caused damage to the eye, the tissues around the eye (the orbit), or the visual pathways. These ...
Fingolimod-Associated Macular Edema is swelling in the center of the retina (the macula) that happens as a side effect of taking the drug fingolimod, which is ...
Filamentary keratitis is a painful eye condition in which thread-like strands (called filaments) form and stick to the surface of the cornea, the clear front ...
Fibrous histiocytoma is a name doctors give to a group of tumors that arise from cells in the skin or soft tissues that look like a mix of fibroblasts (cells ...
Fibrous dysplasia is a rare, non-inherited bone condition in which normal bone and its marrow are gradually replaced by abnormal, weak, fibrous (scar-like) ...
Fetal Alcohol Spectrum Disorders (FASD) is the name for a range of problems that happen when a baby is exposed to alcohol before birth. Alcohol crosses the ...
Festoons are soft, sagging, bag-like swellings that appear on the lower eyelid and upper cheek area, typically forming a “hammock” or bulge over the cheek ...
Familial Retinal Arterial Macroaneurysms (FRAM), also called Retinal Arterial Macroaneurysm with Supravalvular Pulmonic Stenosis (RAMSVPS), is a rare inherited ...
Familial Exudative Vitreoretinopathy, or FEVR, is a rare inherited eye disease that affects how blood vessels grow in the retina, which is the light-sensitive ...
Facial nerve palsy means that the seventh cranial nerve (the facial nerve) is not working properly. This nerve controls the muscles of the face—so when it is ...
Fabry disease is a rare inherited disorder caused by a problem in a single gene called GLA. That gene gives instructions to make an enzyme named ...
An eyelid laceration is a cut or tear in the skin and underlying structures of the eyelid. Eyelids protect the eye, help spread tears to keep the eye moist, ...
An eyelid burn is damage to the skin and tissues of the eyelid caused by heat (thermal), chemicals, radiation, or electricity. Because the eyelid is thin and ...
Eyelash ptosis means that the upper eyelashes bend downward or droop instead of having their normal slight upward curve. Normally, upper eyelashes sweep upward ...
Eye tattooing refers to putting pigment (ink) into parts of the eye to change its appearance. There are two very different contexts: one is therapeutic or ...
Haglund’s deformity is a condition where the back upper part of the heel bone (the posterosuperior calcaneus) becomes abnormally enlarged, forming a bony bump. ...
Eye injury diseases means any damage to the eye or the tissue around it caused by accidents, hits, chemicals, heat, radiation, sharp objects, or other force. ...
Eye banking is a system of collecting, checking, preserving, and giving donated eye tissue—especially corneas—to surgeons who transplant it into people who ...
Warthin tumor (also called papillary cystadenoma lymphomatosum or adenolymphoma) is a benign tumor that usually grows in the parotid salivary gland near the ...
Exudative retinal detachment, also called serous retinal detachment, is when fluid builds up under the retina without any tear or traction pulling it away. The ...
Extraocular Muscle Lymphoma is a rare type of cancer where lymphoma cells grow inside or around the muscles that move the eye (the extraocular muscles). These ...
Exposure keratopathy is damage to the clear front surface of the eye (the cornea) that happens when the eye is not fully protected or wetted by the eyelids and ...
Exotropia is a type of strabismus (eye misalignment) where one or both eyes turn outward, away from the nose. Sometimes it happens all the time, and sometimes ...
Exenteration is a very large, radical surgery done to remove all the organs and tissues from a body cavity when disease—most often cancer—is deeply stuck, has ...
Myopic Laser Vision Correction means using laser surgery to fix myopia, also called nearsightedness. Myopia is when your eye can see things that are close ...
Ethambutol optic neuropathy (EON) is damage to the optic nerve caused by the drug ethambutol, which is used to treat tuberculosis. The optic nerve carries ...
Esthesioneuroblastoma, also known as olfactory neuroblastoma, is a rare cancer that starts from the nerve cells responsible for smell in the upper part of the ...
