Condition library

Eye conditions, explained simply.

Browse common eye conditions with quick answers first, then clear detail on causes, tests, treatment, and when to seek care.

Clinically reviewed · Last reviewed 2026-06-13

Browse by area of the eye

Eyelid conditions Conditions affecting the eyelids, eyelid margin, tear drainage and surrounding tissues. Cornea and front of eye Conditions of the clear front window of the eye, the white of the eye, the lens and common focusing problems. Retina and optic nerve Conditions affecting the light-sensing retina, vitreous gel and optic nerve at the back of the eye. Glaucoma Conditions linked to optic nerve damage from raised eye pressure or other glaucoma mechanisms. Children's eye conditions Conditions that especially affect babies, children and young people, including screening and emergency warning signs. Eye infections Infectious and contagious conditions of the eye surface, eyelids and surrounding tissues. Systemic and whole-body links Eye problems driven by whole-body disease, medicines, or conditions that need joint medical care.

All conditions A–Z

Cataracts Clouding of the lens with age causing blur and glare; surgery replaces the cloudy lens when daily life is affected. Glaucoma Optic nerve damage often linked to eye pressure; the common type is silent until side vision is lost — regular tests are essential. Dry eye Tears too few or evaporating too fast; overlaps with blepharitis and MGD — lubricants, lid care and prescription options help most people. Macular degeneration Age-related loss of central vision affecting the macula; dry AMD is common and slow, wet AMD needs urgent treatment. Diabetic retinopathy Diabetes-related damage to retinal blood vessels; screening finds silent disease, and macular swelling (DME) needs targeted treatment. Conjunctivitis Red, irritated eyes from infection or allergy; the cause guides treatment — viral, bacterial and allergic types need different approaches. Floaters and flashes Drifting spots and brief light flashes are common with age; a sudden shower of floaters or a curtain of vision loss is an emergency. Blepharitis Inflamed eyelid margins causing crusting, grittiness and red rims; daily lid hygiene is the mainstay of control. Stye A painful red lump on the eyelid, usually from a blocked infected lash follicle; warm compresses help most cases settle. Short-sightedness A very common focusing problem where distant objects look blurred; corrected with glasses, lenses or surgery. Astigmatism A common focusing problem from an unevenly curved eye, causing blur at all distances; easily corrected. Presbyopia The normal age-related loss of near focus from around your mid-40s; corrected with reading glasses or lenses. Long-sightedness A common focusing problem where near objects look blurred; corrected with glasses, lenses or surgery. Chalazion A usually painless lump in the eyelid from a blocked oil gland; most clear with warm compresses. Subconjunctival haemorrhage A bright red patch on the white of the eye from a tiny burst vessel; alarming but usually harmless. Watering eyes Excessive tearing from blocked ducts, dryness or irritation; common and often treatable once the cause is found. Colour blindness Usually inherited difficulty telling certain colours apart, most often red and green; not usually serious. Retinal detachment A medical emergency where the retina pulls away from the back of the eye; urgent treatment protects sight. Uveitis Inflammation inside the eye causing pain, redness and blurred vision; needs prompt specialist treatment. Keratoconus The cornea thins and bulges into a cone shape, distorting vision; often starts in the teens or twenties. Pterygium A fleshy growth on the surface of the eye linked to sun exposure; usually harmless but can affect vision if large. Amblyopia (lazy eye) Reduced vision in one eye that did not develop normally in childhood; most treatable when caught early. Squint (strabismus) Eyes that point in different directions; common in children and treatable, and can also affect adults. Droopy eyelid (ptosis) An upper eyelid that droops over the eye; usually age-related and treatable, but a sudden droop needs checking. Entropion (eyelid turning inward) An eyelid that turns inward so the lashes rub the eye; common with age and treatable, often with surgery. Ectropion (eyelid turning outward) A lower eyelid that sags outward, causing watering and dryness; common with age and treatable with surgery. Corneal abrasion (scratched eye) A scratch on the clear front of the eye; painful but usually heals quickly. Chemical splashes need emergency care. Ocular migraine (visual aura) Temporary visual disturbances like zigzags or shimmering from migraine; usually harmless and short-lived. Eye twitching (eyelid twitch) A common, harmless fluttering of the eyelid, usually linked to tiredness, stress or caffeine. Retinitis pigmentosa A group of inherited conditions that slowly break down the retina, often starting with night and side vision. Ocular rosacea Eye irritation linked to the skin condition rosacea; manageable with eyelid care and treatment. Pinguecula A harmless yellowish bump on the white of the eye, linked to sun and dust exposure. Digital eye strain Tired, dry, achy eyes from long screen use; eased by breaks, blinking and screen setup. Ocular hypertension Higher-than-normal eye pressure without glaucoma damage; monitored to protect sight. Posterior vitreous detachment A common, usually harmless age-related change causing floaters and flashes; needs checking to rule out a retinal tear. Contact lens discomfort Sore, dry or red eyes with lenses often signals fit, hygiene or surface disease problems — stop lenses and seek advice if pain or vision drops. Corneal ulcer An open sore on the cornea, often from infection; a sight-threatening emergency needing urgent care. Nystagmus Involuntary, repetitive eye movements that can affect vision; managed with support and treating any cause. Eye allergies Itchy, red, watery eyes from pollen, dust or pets; seasonal peaks in spring and summer respond well to trigger avoidance and allergy drops. Blepharospasm Involuntary, forceful eyelid spasms or closure; different from minor twitching and often treated with injections. Thyroid eye disease Eye changes linked to thyroid problems, causing bulging, dryness and double vision; needs specialist care. Scleritis Painful, deep inflammation of the white of the eye, often linked to autoimmune disease; needs prompt care. Optic neuritis Inflammation of the optic nerve causing sudden vision loss or pain on eye movement; needs urgent assessment. Retinal vein occlusion A blocked vein at the back of the eye causing sudden blurred vision; needs prompt eye assessment. Central serous retinopathy Fluid under the retina causing blurred or distorted central vision, often in stressed middle-aged men. Episcleritis A mild, usually painless red eye from surface inflammation; different from the more painful scleritis. Herpes eye infection A cold-sore virus infection of the cornea causing a painful red eye; needs prompt antiviral treatment. Macular hole A small gap in the central retina causing distorted or missing central vision; often treated with surgery. Retinal artery occlusion Blocked retinal artery causing sudden painless vision loss; brief episodes (amaurosis fugax) are stroke warnings needing emergency assessment. Blocked tear duct Tears cannot drain properly, causing a watery or sticky eye; common in babies and adults. Shingles in the eye Shingles affecting the eye area can threaten sight; the rash and eye pain need urgent specialist care. Fungal eye infection A rare but serious corneal infection, often linked to contact lens wear or eye injury; needs urgent specialist care. Photokeratitis (arc eye) Sunburn of the cornea from UV light, welding arcs or snow glare; painful but usually heals in days. Chemical eye injury Splash of chemicals into the eye is an emergency; immediate flushing can save sight. Hyphema Blood in the front of the eye after injury; needs urgent assessment to protect vision and eye pressure. Orbital cellulitis Deep infection around the eye causing painful swelling and often fever; a medical emergency. Dacryocystitis Infection of the tear sac causing a painful, swollen lump by the nose; needs antibiotics. Foreign body in the eye Something in the eye causes pain and watering; do not rub, and seek help for metal or plant material. Viral conjunctivitis Very contagious watery pink eye, often after a cold; antibiotics do not help — hygiene and time are the main treatment. Lattice degeneration Thinning at the edge of the retina, common and usually harmless but linked to retinal tears in some people. Vitreous haemorrhage Bleeding into the gel inside the eye causing sudden floaters or vision loss; needs urgent assessment. Retinal tear A split in the retina that can lead to detachment; new flashes and floaters need same-day care. Fuchs dystrophy Gradual corneal swelling causing morning blur and glare, usually in older adults; treatable with drops or surgery. Trachoma A leading infectious cause of blindness worldwide, spread by contact and flies; preventable with hygiene and WHO programmes. Bacterial conjunctivitis Sticky yellow-green discharge and glued lids, often needing antibiotic drops after assessment; more urgent in babies and contact-lens wearers. Black eye Bruising and swelling around the eye after a blow; usually heals in days but needs checking if vision changes. Eye cancer (ocular melanoma) A rare cancer inside or on the eye; may have few early symptoms, so eye checks matter. Endophthalmitis Severe infection inside the eye after surgery or injury; a sight-threatening emergency. Papilloedema Swelling of the optic nerve from raised pressure around the brain; causes headaches and vision changes. Iritis Inflammation at the front of the eye causing a painful, red, light-sensitive eye; needs prompt steroid treatment. Retinopathy of prematurity Abnormal blood vessel growth in premature babies' retinas; screened and treated to prevent vision loss. Onchocerciasis (river blindness) A parasitic eye disease spread by black flies; a WHO-targeted cause of preventable blindness in affected regions. Vitamin A deficiency and the eye Lack of vitamin A dries the eye surface and is a leading preventable cause of childhood blindness worldwide. Leprosy and the eyes Leprosy can damage nerves that protect the eye surface, causing dryness, lagophthalmos and preventable corneal blindness. Lymphatic filariasis A mosquito-spread parasitic disease targeted by WHO; endemic in parts of Indonesia and tropical regions, with rare eye complications. Cysticercosis and the eye Tapeworm larvae can lodge in the eye in endemic areas; causes vision loss if untreated — a WHO neglected tropical disease. Giant cell arteritis Inflammation of scalp arteries in older adults; headache, jaw pain and sudden vision loss are emergencies. Charles Bonnet syndrome Visual hallucinations in people with significant sight loss; distressing but not a mental illness — needs understanding and support. Retinoblastoma A rare childhood eye cancer; a white pupil reflex in photos or a squint needs urgent specialist assessment. Meibomian gland dysfunction Blocked or poor-quality eyelid oil glands that drive dry, gritty eyes; often improves with warm compresses and lid hygiene. Sjögren's syndrome and the eye An autoimmune condition that often causes severe dry eye and mouth; lifelong monitoring and tailored dry-eye care help. Diabetic macular oedema Fluid swelling at the macula from diabetes; blurs central vision but is treatable when found early on screening. Acanthamoeba keratitis A rare but serious corneal infection linked to contact lenses and water exposure; painful red eye needs urgent specialist care. Epiretinal membrane A thin scar-like sheet on the macula that can warp central vision; many cases are mild and only some need surgery.

Common conditions

Start with the conditions people search for most often.

Cataracts
Glaucoma
Dry eye disease
Age-related macular degeneration
Diabetic eye disease

How each guide is structured

Every condition page opens with a quick answer and red flags, then covers causes, diagnosis, treatment options, and follow-up in plain language.

When to seek care

Each guide clearly separates routine concerns from symptoms that need same-day or emergency attention.

Frequently asked questions

What are the most common eye conditions?

Cataracts, glaucoma, dry eye disease, age-related macular degeneration, and diabetic eye disease are among the most common, and most are manageable when found early.

Can eye conditions be prevented?

Many cannot be fully prevented, but regular eye exams, managing conditions like diabetes, eye protection, and not ignoring new symptoms can reduce risk and slow progression.

When should I see an eye specialist?

Book a routine exam if you notice gradual changes, and seek same-day care for sudden vision loss, severe pain, eye injury, or new flashes and floaters.

What is the difference between an optician, optometrist and ophthalmologist?

An optician fits glasses and contact lenses. An optometrist examines eyes, prescribes glasses, and can manage many common conditions. An ophthalmologist is a medical eye doctor who treats disease and performs surgery.

Can children have serious eye conditions?

Yes. Amblyopia, squint, and retinopathy of prematurity are examples where early childhood checks matter. Never ignore a white pupil reflex or a turned eye in a child.

Does diabetes affect the eyes?

Yes. Diabetic retinopathy can damage sight without early symptoms. People with diabetes should attend retinal screening as advised and keep blood sugar and blood pressure well controlled.

Are eye drops from the pharmacy always safe?

Over-the-counter lubricating drops are usually safe for short-term dryness, but redness-relief drops can mask serious problems. Do not use steroid or antibiotic drops without professional advice.

What are red-flag eye symptoms?

Sudden vision loss, severe pain, injury, chemical splash, new flashes with floaters, a curtain over vision, painful red eye with light sensitivity, and double vision with neurological symptoms.