Eye Diseases: The Complete Guide to Symptoms, Causes, Diagnosis and Treatment
Updated: 6 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 17, 2026
Quick Answer
Eye diseases are medical problems affecting any part of the eye or the structures around it, such as the eye muscles, socket and eyelids. The most common worldwide are cataracts, refractive errors, glaucoma, age-related macular degeneration and diabetes-related retinopathy. Treatments range from eyeglasses and contact lenses to surgery and medications, and many conditions are easier to treat when caught early.
What the research says
Cataract is the leading cause of blindness in older adults. A systematic review and meta-analysis for the Global Burden of Disease Study found that the leading global causes of blindness in people aged 50 and older in 2020 were cataract (15.2 million cases), glaucoma (3.6 million), undercorrected refractive error (2.3 million), age-related macular degeneration (1.8 million), and diabetic retinopathy (0.86 million); the leading causes of moderate and severe vision impairment were undercorrected refractive error (86.1 million) and cataract (78.8 million) (PubMed: GBD 2019 Blindness and Vision Impairment Collaborators, Lancet Glob Health, 2021).
Rates of blindness are falling, but the number of people affected keeps rising. An analysis of population-based surveys estimated that in 2020, 43.3 million people were blind, 295 million had moderate and severe vision impairment, and 510 million had vision impairment from uncorrected presbyopia; between 1990 and 2020 the age-standardised prevalence of blindness fell by 28.5% in adults aged 50 and older, yet the number of blind people rose by 50.6% and those with moderate and severe impairment by 91.7% (PubMed: GBD 2019 Blindness and Vision Impairment Collaborators, Lancet Glob Health, 2021).
What Are Eye Diseases? An Overview
Eye diseases are conditions that affect any part of your eye, and they also include conditions that affect the structures immediately around your eyes. These conditions can be acute, meaning they develop quickly, or chronic, meaning they develop more slowly and last a long time.
Your eyeball itself is where most eye diseases happen, but it isn't the only place. Eye diseases also include conditions that can affect your eye muscles, eye socket, eyelids, or the skin and muscles immediately around your eyes.
Medical science knows of hundreds of eye diseases, and they're some of the most common conditions in the world. Many are treatable, especially when caught early.
Key Point | What It Means |
Definition | Conditions affecting any part of the eye or the structures immediately around it |
Speed of onset | Acute (fast) or chronic (slow, long-lasting) |
How many exist | Hundreds of known eye diseases |
How common | Extremely common — the World Health Organization estimates over 2.2 billion people have some form of vision impairment or blindness |
Where they happen | Mostly the eyeball, but also eye muscles, socket, eyelids and surrounding skin/muscles |
Treatability | Many are treatable, especially when caught early; many are curable |
How common are eye diseases?
In general, eye diseases and vision disorders are extremely common. The World Health Organization estimates that over 2.2 billion people have some form of vision impairment or blindness.
One reason that eye diseases are so common is that your eyes don't exist in isolation from the rest of your body. In fact, the opposite is true. Many conditions that affect your eyes happen because of — or in connection with — conditions affecting other body systems. That's why there are hundreds of different conditions that can affect your eyes.
What are the most common eye diseases?
The most common eye diseases worldwide are listed below.
Condition | What It Is |
Cataracts | Clouding of the eye's natural lens |
Refractive errors | Astigmatism, farsightedness (hyperopia), nearsightedness (myopia) and age-related loss of up-close focusing (presbyopia) |
Glaucoma | Damage to the optic nerve, often linked to eye pressure |
Age-related macular degeneration | Breakdown of the central retina (macula) with age |
Diabetes-related retinopathy | Retina damage caused by diabetes |
Eye injuries are also a leading cause of vision loss and blindness. Experts track and research them like diseases to find better ways to prevent and treat eye injuries.
Eye cancers and tumors, while rare, do sometimes happen, but often they're detectable with regular eye exams. Fortunately, many eye tumors are benign (noncancerous). These benign growths may still need removal to prevent them from affecting nearby tissues, but aren't a greater threat.
What are the different types of eye diseases?
There are many types of eye diseases, but there are a few main ways to organize them.
Organization Method | What It Sorts By |
Structure | What specific part(s) of the eye they affect |
Underlying cause | Primary (start in the eye) vs. secondary (start elsewhere in the body, later affect the eye) |
Effect | What symptoms they cause, or what functions they affect or disrupt |
Duration | Acute (very short-lived, like eye infections) vs. chronic (months, years, or a lifetime) |
When talking about eye diseases, it's also important to know the difference between sight and vision.
Term | Definition |
Sight | Starts when light enters through the cornea and ends when light lands on the retina |
Vision | Covers every step of your visual sense, including sight — plus how your nervous system handles and processes visual signals into what you see |
While many people — experts included — frequently use "vision" and "sight" interchangeably, they aren't always the same thing. Sight-related diseases are specific to your eyes, while vision-related diseases can involve your brain and optic nerves, too. That's why some diseases can cause vision loss even though your eyes work just fine.
Symptoms of Eye Diseases
There are many possible symptoms of eye diseases. Those symptoms usually happen in a few key ways.
Symptom Category | What It Includes | Examples |
Symptoms you can feel | Physical sensations in or around the eye | Pain, irritation, eye tiredness or strain |
Changes in eye functions | How the eye works | Watery eyes (epiphora), trouble controlling how you blink |
Changes in appearance | How the eye looks | Yellowing of the white of your eyes (scleral icterus), red eyes, pupils that are too narrow (miosis) |
Changes in movement or alignment | How the eyes sit and move | Outward-turning (exotropia) or inward-turning (esotropia) eyes |
Changes in how you see | Vision itself | Double vision (diplopia), blurred vision, tunnel vision (peripheral vision loss) |
Eye disease symptoms fall into five groups — things you feel (pain, irritation, eye strain), function changes (watery eyes, blinking trouble), appearance changes (yellowing or redness of the eye, unusually narrow pupils), movement/alignment changes, and changes in how you see (double vision, blurred vision, tunnel vision).
What Causes Eye Diseases?
Eye diseases can happen for many, many reasons. Some are direct causes while others are contributing or risk factors.
Cause or Risk Factor | How It Affects Your Eyes |
Genetics | Your DNA is a key part of how your eyes develop and work, and DNA changes (mutations) can cause many eye conditions — the genetic form of color blindness is an example |
Developmental differences | Differences in how your eyes form and develop, starting while you were a developing fetus or at some point during childhood |
Environmental factors | Ultraviolet light exposure, humidity and temperature, dust or particles in the air, and many other variables |
Infectious diseases | Viruses, bacteria, fungi and parasites can infect your eyes directly or spread from elsewhere in your body |
Other chronic conditions | Eyes are vulnerable to body-wide conditions like high blood pressure (hypertension), Type 2 diabetes and several types of thyroid disease |
Previous eye injuries | Events that damage your eye can make you more prone to developing certain eye diseases |
Idiopathic causes | "Idiopathic" means the cause is unknown — no cause experts can identify, though this can sometimes change over time |
Eye diseases have many potential causes, and they can also be idiopathic, meaning their cause is unknown.
How Are Eye Diseases Diagnosed?
An eye care specialist or other healthcare provider can diagnose eye diseases using a combination of methods. The first and foremost tool for diagnosing these diseases is an eye exam.
Eye exams can be routine and happen every one to two years like a regular wellness check. Providers can also do exams in a more specific way when you have signs or symptoms of an eye condition. Certain parts of an eye exam, like pupil dilation and a slit lamp exam, can be especially useful.
Test | What It Does |
Routine eye exam | The first and foremost diagnostic tool; includes checking visual acuity (how well you see) |
Pupil dilation | Expands the pupil so the inside of the eye can be examined |
Slit lamp exam | Magnified exam of the eye's structures |
Fluorescein angiography | Detailed imaging of blood vessels in the eye |
Tonometry | Measures pressure inside the eye |
Retinal imaging | Captures detailed pictures of the retina |
Corneal topography | Maps the shape and surface of the cornea |
Optical coherence tomography | Cross-sectional imaging of eye tissue layers |
Your eye specialist may also recommend more specific eye tests, and many other tests that aren't eye-specific can help, too.
Non-Eye-Specific Test | What It Looks For |
Blood tests | Specific chemical markers related to immune conditions or infections; DNA and genetic tests |
Ultrasound | Imaging of the eye and surrounding structures |
CT scan (computed tomography) | Detailed cross-sectional imaging of the head and eye area |
MRI (magnetic resonance imaging) | Detailed imaging of the eyes, optic nerves and brain |
EEG (electroencephalogram) | Neurological test analyzing brain activity |
Your eye care specialist or other healthcare provider can tell you more about any other tests they recommend, including how those tests work and how they may help you.
How Are Eye Diseases Treated?
Eye disease treatments can vary even more than the conditions they treat. Some treatments can help with many conditions. Others are very specific, meaning they won't help with anything but the conditions they're meant to treat.
Treatment Option | Used For |
Corrective lenses (eyeglasses) | Most commonly for refractive errors — adjust eyesight and improve visual acuity |
Corrective lenses (contact lenses) | Most commonly for refractive errors — adjust eyesight and improve visual acuity |
Vision correction surgery | Especially laser-based surgeries like LASIK |
Eye surgeries | Including glaucoma surgery and cataract surgery |
Medications | Condition-specific medical treatment |
Refractive errors are some of the most common eye conditions. They're also usually easier to treat, with corrective lenses like eyeglasses or contact lenses helping to adjust eyesight and improve visual acuity.
Because the treatments can vary so widely and be so specific, your eye care specialist is the best source of information about treatments for your specific needs. They can also tell you about possible side effects, complications and more.
Can Eye Diseases Be Prevented?
Some eye diseases are completely preventable, and you can at least reduce your risk of developing others. But many eye diseases happen unpredictably, making it impossible to prevent or lower the odds of having them.
Prevention Step | Why It Matters |
Get regular eye exams | Everyone, even people who don't wear corrective lenses, should get an eye exam at least every one to two years (more often with risk conditions) |
Wear eye protection | Purpose-made eye protection prevents eye injuries or makes them less severe — regular eyeglasses can't do the same job |
Avoid nicotine use | Smoking, vaping and smokeless tobacco affect your circulatory system, especially the blood vessels that supply your eyes |
Don't ignore infections | An eye infection lasting more than a few days needs a provider visit — untreated infections can cause lasting damage |
Don't ignore eye symptoms | Gradual vision changes mean you need an eye exam; sudden, unexpected vision changes — especially vision loss — are medical emergencies needing immediate care |
Make proper nutrition a priority | Your eyes need specific vitamins and minerals to do their best |
Reach and maintain a healthy weight | Overall health has a big impact on eye health |
Living With Eye Diseases
If you've been told you have an eye disease, start with your eye care specialist's treatment plan and keep every follow-up appointment. Routine monitoring matters because many eye conditions progress silently — some, like glaucoma, can cause permanent damage before you notice symptoms. Keep your routine eye exams every one to two years, and report any new or worsening symptoms right away.
When should you see your healthcare provider?
Gradual vision changes are a sign that you need to see an eye care specialist for an eye exam. And sudden, unexpected vision changes — especially vision loss — are medical emergencies that need immediate care.
What are some common children's eye conditions?
Children can have many eye conditions that adults have. Some of the most common include:
Childhood Eye Condition | What It Is |
Eye misalignment (strabismus) | Eyes that don't point in the same direction |
Lazy eye (amblyopia) | Reduced vision in one eye from abnormal visual development |
Retinoblastoma | A rare eye cancer of childhood |
Coloboma | A missing piece of tissue in structures of the eye |
Tear duct conditions (dacryocystitis) | Infection or blockage of the tear drainage system |
An important detail about many childhood eye diseases like strabismus and lazy eye is that they're much easier to treat during early childhood. If you have concerns about whether a child you care for has an eye condition like this, talk to their pediatrician or another healthcare provider.
A note about how eye diseases feel
It's still normal to experience difficult or unpleasant feelings when you learn you have an eye condition. The type and severity of these conditions vary widely, but most are treatable, and many are curable. Regular eye exams are essential and can help catch these conditions early, when it's more likely they'll be easier to treat.
Conclusion: Protect Your Vision Before You Lose It
Eye diseases are among the most common conditions in the world — the World Health Organization estimates over 2.2 billion people have some form of vision impairment or blindness. They affect the eyeball, the eye muscles, the socket, the eyelids and the tissue around them, and they come in acute and chronic forms driven by genetics, environment, infection and body-wide conditions. The good news is that most are treatable, many are curable, and the single most powerful step you can take is a routine eye exam every one to two years.
Important: If a healthcare provider diagnosed you with an eye disease, follow their treatment plan. And if you experience sudden, unexpected vision changes — especially sudden vision loss — go to the emergency room for immediate care.
Take the Next Step
Protect your eyes — schedule a routine eye exam today. If you have concerns about your vision, talk to an eye care specialist. They can offer guidance, support and reassurance as you work together to manage any conditions you face.
Related on Rinnit: Cataracts · Diabetic retinopathy · Farsightedness (hyperopia) · Presbyopia · Double vision (diplopia) · Watery eyes (epiphora) · Esotropia · Retinoblastoma · Dacryocystitis
Further reading: Cleveland Clinic — Eye Diseases
Frequently Asked Questions
1. What are eye diseases?
Eye diseases (sometimes called eye conditions) are medical problems that affect any part of your eye, including the eye muscles, eye socket, eyelids, and the skin and muscles immediately around your eyes. They can be acute (develop quickly) or chronic (develop slowly and last a long time).
2. How common are eye diseases?
Extremely common. The World Health Organization estimates that over 2.2 billion people worldwide have some form of vision impairment or blindness. Many eye conditions are connected to conditions affecting other body systems, which is why hundreds of different eye diseases exist.
3. What are the most common eye diseases?
The most common eye diseases worldwide are cataracts, refractive errors (astigmatism, farsightedness, nearsightedness, presbyopia), glaucoma, age-related macular degeneration and diabetes-related retinopathy. Eye injuries are also a leading cause of vision loss and blindness.
4. Can eye diseases cause vision loss even if the eyes are healthy?
Yes. Sight is specific to the eyes — light entering the cornea and landing on the retina — but vision includes how your brain and optic nerves process visual signals. Vision-related diseases can involve the brain and optic nerves, so some diseases cause vision loss even though the eyes themselves work fine.
5. What is the difference between primary and secondary eye diseases?
Primary eye diseases start in your eye. Secondary eye diseases happen because of a condition elsewhere in your body — such as high blood pressure, Type 2 diabetes or thyroid disease — that later affects your eye.
6. What are the symptoms of eye diseases?
Symptoms fall into five groups: things you feel (pain, irritation, eye strain), function changes (watery eyes, trouble controlling blinking), appearance changes (yellowing or redness of the eye, unusually narrow pupils), movement or alignment changes (eyes turning in or out), and changes in how you see (double vision, blurred vision, tunnel vision).
7. What causes eye diseases?
Causes include genetics and DNA mutations, developmental differences starting in the womb or childhood, environmental factors like UV light and dust, infections from viruses, bacteria, fungi and parasites, body-wide chronic conditions (hypertension, diabetes, thyroid disease), previous eye injuries, and idiopathic (unknown) causes.
8. How are eye diseases diagnosed?
The first and foremost tool is an eye exam, which can be routine every one to two years or symptom-driven. Especially useful parts include pupil dilation and slit lamp exam. Specific tests include fluorescein angiography, tonometry, retinal imaging, corneal topography and optical coherence tomography, plus non-eye tests like blood work, CT, MRI and EEG.
9. How are eye diseases treated?
Refractive errors are usually treated with corrective lenses (eyeglasses or contacts). Other common treatments include laser-based vision correction surgery such as LASIK, eye surgeries like glaucoma and cataract surgery, and medications. Because treatments vary widely, your eye care specialist is the best source for your specific needs.
10. Can eye diseases be prevented?
Some are completely preventable and others are not — many happen unpredictably. Key steps: eye exams every one to two years, purpose-made eye protection, avoiding nicotine, not ignoring infections or eye symptoms, proper nutrition, and maintaining a healthy weight.
11. When should I go to the ER for an eye problem?
Sudden, unexpected vision changes — especially sudden vision loss — are medical emergencies that need immediate care. Also seek prompt care for eye infections lasting more than a few days, since untreated infections can cause lasting damage.
References
GBD 2019 Blindness and Vision Impairment Collaborators; Vision Loss Expert Group of the Global Burden of Disease Study. Causes of blindness and vision impairment in 2020 and trends over 30 years, and prevalence of avoidable blindness in relation to VISION 2020: the Right to Sight: an analysis for the Global Burden of Disease Study. Lancet Glob Health. 2021;9(2):e144-e160. doi:10.1016/S2214-109X(20)30489-7. PMID: 33275949.
GBD 2019 Blindness and Vision Impairment Collaborators; Vision Loss Expert Group of the Global Burden of Disease Study. Trends in prevalence of blindness and distance and near vision impairment over 30 years: an analysis for the Global Burden of Disease Study. Lancet Glob Health. 2021;9(2):e130-e143. doi:10.1016/S2214-109X(20)30425-3. PMID: 33275950.
Cleveland Clinic. Eye diseases. Cleveland Clinic Health Library. Medically reviewed; last updated May 2, 2024. https://my.clevelandclinic.org/health/diseases/eye-diseases
Medical Disclaimer
This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here.
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