Eye Diseases; Causes, Types / Classification, Treatment

Eye Diseases

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Eye Diseases also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some also include those who have a decreased ability to see because they do not have access to glasses or contact lenses. Visual impairment is often defined as a best corrected visual acuity of worse than either 20/40 or 20/60. The term blindness is used for complete or nearly complete vision loss. Visual impairment may cause people difficulties with normal daily activities such as driving, reading, socializing, and walking.

Cause of Eye Diseases

The most common causes of visual impairment globally in 2010 were:

  • Refractive error (42%)
  • cataract (33%)
  • glaucoma (2%)
  • age related macular degeneration (1%)
  • corneal opacification (1%)
  • diabetic retinopathy (1%)
  • childhood blindness
  • trachoma (1%)
  • undetermined (18%)

The most common causes of blindness in 2010 were

  • cataracts (51%)
  • glaucoma (8%)
  • age related macular degeneration (5%)
  • corneal opacification (4%)
  • childhood blindness (4%)
  • refractive errors (3%)
  • trachoma (3%)
  • diabetic retinopathy (1%)
  • undetermined (21%)

About 90% of people who are visually impaired live in the developing world. Age-related macular degeneration, glaucoma, and diabetic retinopathy are the leading causes of blindness in the developed world.

Among working age adults who are newly blind in England and Wales the most common causes in 2010 were

  • Hereditary retinal disorders (20.2%)
  • Diabetic retinopathy (14.4%)
  • Optic atrophy (14.1%)
  • Glaucoma (5.9%)
  • Congenital abnormalities (5.1%)
  • Disorders of the visual cortex (4.1%)
  • Cerebrovascular disease (3.2%)
  • Degeneration of the macula and posterior pole (3.0%)
  • Myopia (2.8%)
  • Corneal disorders (2.6%)
  • Malignant neoplasms of the brain and nervous system (1.5%)
  • Retinal detachment (1.4%)

Types Eye Diseases

Definitions of Vision Disorders in the Vision in Preschoolers Study.

Vision Disorder Definitions
Hyperopia Any hyperopia: >3.25 D in most positive meridian in either eye
Hyperopia severity:
 Group 1: ≥5.0 D
 Group 2: >3.25D and <5.0D and interocular difference in SE of ≥0.5 D
 Group 3: >3.25D and <5.0D and interocular difference in SE of <0.5 D
Anisometropia >1.00D interocular difference in hyperopia; >3.00D interocular difference in myopia; >1.50D interocular difference in astigmatism; antimetropic difference >1.00D and one eye >1.00D of hyperopia; antimetropic difference >3.00D and one eye >2.00D of myopia
Astigmatism >1.50D between principal meridians
Unilateral Amblyopia ≥2-line interocular difference in VA and a unilateral amblyogenic factor
Bilateral Amblyopia 3-year-olds : worse than 20/50 in one eye, worse than 20/40 in the contralateral eye, and a bilateral amblyogenic factor
4- and 5-year olds: worse than 20/40 in one eye, worse than 20/30 in the contralateral eye, and a bilateral amblyogenic factor
Strabismus Any heterotropia in primary gaze

D=diopters; VA=Visual Acuity

Strabismus, anisometropia and a difference in spherical equivalent of ≥0.50D when ≥1 eye had >3.50D of hyperopia were considered unilateral amblyogenic factors.
Astigmatism of >2.50 D, hyperopia of >5.00 D, or myopia of >8.00 D in each eye were considered bilateral factors.

Amblyopia -is a category of vision loss or visual impairment that is caused by factors unrelated to refractive errors or coexisting ocular diseases. Amblyopia is the condition when a child’s visual systems fail to mature normally because the child either suffers from a premature birth, measles, congenital nubella syndrome, vitamin A deficiency, or meningitis. If left untreated during childhood, amblyopia is currently incurable in adulthood because surgical treatment effectiveness changes as a child matures. Consequently, amblyopia is the world’s leading cause of child monocular vision loss, which is the damage or loss of vision in one eye. In the best case scenario, which is very rare, properly treated amblyopia patients can regain 20/40 acuity.

  • Corneal opacification
  • Degenerative myopia
  • Diabetic retinopathy – is one of the manifestation microvascular complications of diabetes, which is characterized by blindness or reduced acuity. That is, diabetic retinopathy describes the retinal and vitreous hemorrhages or retinal capillary blockage caused by the increase of A1C, which a measurement of blood glucose or sugar level. In fact, as A1C increases, people tend to be at greater risk of developing diabetic retinopathy than developing other microvascular complications associated with diabetes (e.g. chronic hyperglycemia, diabetic neuropathy, and diabetic nephropathy). Despite the fact that only 8% of adults 40 years and older experience vision-threatening diabetic retinopathy (e.g. nonproliferative diabetic retinopathy or NPDR and proliferative diabetic retinopathy or PDR), this eye diseased accounted for 17% of cases of blindness in 2002.
  • Retinitis pigmentosa
  • Retinopathy of prematurity – The most common cause of blindness in infants worldwide. In its most severe form, ROP causes retinal detachment, with attendant visual loss. Treatment is aimed mainly at prevention, via laser or Avastin therapy.
  • Stargardt’s disease
  • Uveitis – is a group of 30 intraocular inflammatory diseases caused by infections, systemic diseases, organ-specific autoimmune processes, cancer or trauma. That is, uveitis refers to a complex category of ocular diseases that can cause blindness if either left untreated or improperly diagnosed. The current challenge of accurately diagnosing uveitis is that often the cause of a specific ocular inflammation is either unknown or multi-layered. Consequently, about 3–10% uveitis victims in developed countries, and about 25% of victims in the developing countries, become blind from incorrect diagnosis and from ineffectual prescription of drugs, antibiotics or steroids. In addition, uveitis is a diverse category of eye diseases that are subdivided as granulomatous (or tumorous) or non-granulomatous anterior, intermediate, posterior or pan uveitis. In other words, uveitis diseases tend to be classified by their anatomic location in the eye (e.g. uveal tract, retina, or lens), as well as can create complication that can cause cataracts, glaucoma, retinal damage, age-related mac

The Most Common Eye Disease 

Acanthamoeba Keratitis

A rare but serious eye infection associated with poor contact lens hygiene and other factors.

Acanthamoeba Keratitis

Amblyopia (Lazy Eye)

Amblyopia is a vision development problem in infants and young children that can lead to permanent vision loss. Learn the symptoms, causes and treatments.

eye-diseases-Amblyopia (Lazy Eye)


Is one pupil bigger than the other? Learn about anisocoria (unequal pupils).



Usually caused by an irregular cornea, astigmatism causes blur at all distances. Also see the Eye Doctor

eye diseases Astigmatism

Bell’s Palsy

This condition causes sudden paralysis of one side of the face. Because it affects blinking, it can cause severe dry eye.

Bionic Eye Implants

Learn about retinal implants that are restoring functional vision to people with retinitis pigmentosa and other blinding conditions.

eye diseases Bionic Eye Implants

Black Eye

How serious is a black eye? How to treat black eyes.

eye diseases Black Eye


Inflammation of the eyelids associated with chronic eye irritation, watery eyes, foreign body sensation, sensitivity to light and crusty debris at the base of the eyelashes.

eye diseases Blepharitis

Blurry Vision

Blurry vision has many causes, from fatigue and eyestrain to serious eye diseases such as glaucoma. A video helps explain blurry vision causes and treatments.

eye diseases ,Blurry Vision

Burning Eyes

How to get relief from burning, stinging eyes.

eye diseases ,Burning Eyes


The risk of cataracts increases with age. Learn what causes them and how to protect your eyes.

eye diseases, Cataracts


A swollen bump in the eyelid. Learn about causes and treatments.

eye diseases ,Chalazion

Clinical Trials Related to Eye Diseases

Find out the status of clinical trials for treatment of glaucoma, macular degeneration, blepharitis and other eye problems and diseases.

CMV Retinitis

About 80 percent of adults have been exposed to the cytomegalovirus (CMV), but it mostly affects people with poor immune systems, such as AIDS patients.

eye diseases, CMV Retinitis

Color Blindness

Learn the varieties of color vision deficiency and how to cope with color blindness.

eye diseases ,Color Blindness

Common Eye Disorders

How to identify and manage everyday eye problems.

Concussion, TBI and Vision

Up to 90 percent of people who suffer from concussion or other traumatic brain injury experience vision problems such as blurry vision, sensitivity to light and difficulties with eye movements. Learn what can be done.

eye disease ,TBI and Vision

Conjunctivitis (Pink Eye)

What you can do about redness, swelling, itching and tearing of pink eye.

eye diseases, Conjunctivitis

Cornea Transplant

Eye injuries and diseases like keratoconus may require a cornea transplant, using healthy tissue from an eye donor.

eye diseases, Cornea Transplant

Corneal Abrasion (Scratched Eye)

A scratched cornea is usually very painful. What to do if it happens to you.

eye disease ,Corneal Abrasion

Corneal Collagen Crosslinking

Not yet FDA-approved, these procedures can strengthen the front surface of the eye and help keratoconus patients avoid a cornea transplant.

eye diseases,Corneal Collagen Crosslinking

Corneal Ulcer

Treatment may help prevent scarring on your eye.

eye diseases, Corneal Ulcer

Detached Retina

Flashes of light and floating spots are classic warning signs of a detached retina — get them checked out ASAP.

eye disease-Detached Retina

Diabetic Retinopathy

Damage to the eye’s retina due to diabetes. Also read about treatment for diabetic retinopathy and macular edema.

Different Colored Eyes (Heterochromia)

Many people (and animals) have two different colored eyes. What causes it? Is it a problem that requires an eye exam?

eye diseases Different Colored Eyes

Double Vision (Diplopia)

Many conditions cause double vision, including stroke and cataracts. What to do.

eye diseases -Double Vision

Dry Eye Infographic 

Learn eight symptoms, causes and steps to managing dry eye.

Dry Eye Infographic

Eye Allergies

Itchy, red, swollen, tearing eyes may mean eye allergies. Get tips for relief, and read our Eye Doctor Q&Aabout common eye allergy symptoms.

eye diseases Eye Allergies

Eye and Vision Product News

New eyewear and vision care products designed to improve your life.

Eye Herpes

Ocular herpes is a recurrent viral infection that may lead to serious vision loss. Read how herpes of the eye is transmitted and treated.

Eye Infections

Learn about bacterial, viral and fungal eye infections, including symptoms.

eye diseases Eye Infections

Eye Injury

Accidents cause many kinds of eye injuries, from corneal scratches to penetrating wounds. What to do for an eye emergency.

eye diseases Eye Injury

Eye Occlusions (Eye Strokes)

Sudden vision loss can occur when a clot or blockage interrupts blood flow to vital eye structures.

eye diseases Eye Occlusions

Eye Pain

How to know if a painful eye is an emergency.

Eye Pain

Eye Twitching

Eyelid twitches, tics and spasms are maddening. Here are eight remedies you can try.

eye-diseases-Eye Twitching

Floaters, Flashes and Spots

Eye floaters and flashes may be harmless, or they may signal a serious problem, like a detached retina.

Fuchs’ Corneal Dystrophy

Causes loss of vision and clouding of the cornea due to degeneration of the corneal endothelium and corneal edema.

eye diseases,Fuchs' Corneal Dystrophy


Glaucoma damages the optic nerve and diminishes the field of vision. Learn about glaucoma causes, eye drops for glaucoma, narrow-angle glaucoma, primary open-angle glaucoma and glaucoma surgery.

eye diseases Glaucoma

Glaucoma Surgery

New options for controlling glaucoma with surgery.

eye diseases Glaucoma Surgery

Higher-Order Aberrations

Higher-order aberrations (HOAs) are vision errors causing poor night vision or double images.

eye diseases Higher-Order Aberrations

Hyperopia (Farsightedness)

Farsighted people can have poor near vision or blurred vision at all distances.

eye diseases, Hyperopia


A hyphema is a broken blood vessel in the eye that causes blood to collect in the space between the cornea and iris. It’s usually painful and can cause glaucoma.

eye diseases-Hyphema 

Intacs for Keratoconus

These tiny corneal inserts can help flatten a bulging eye.

https://www.rxharun.com/eye diseases Intacs for Keratoconus

Itchy Eyes

What causes itchy eyes and eyelids — and how to get relief.

eye diseases Itchy Eyes


Special contact lenses can help this condition that changes the shape of your eye.

eye diseases -Keratoconus

Macular Degeneration (AMD)

Our 10-page section covers this sight-threatening disease, plus FDA-approved macular degeneration treatments, investigational treatments, macular degeneration prevention,

eye diseases Macular Degeneration

Macular Dystrophy

Central vision loss can be associated with this inherited eye disease.

eye diseases -Macular Dystrophy

Macular Hole

Suddenly blurry or distorted vision, especially in seniors and diabetics, may mean a macular hole.

eye diseases-Macular Hole

Meibomian Gland Dysfunction

MGD is the culprit behind most cases of dry eye syndrome. Find out how to spot it and what you can do to get relief.

https://www.rxharun.com/eye diseases,

Milia (Eyelid Cysts) 

What causes those tiny eyelid cysts in babies and adults, and how they are treated.

Myopia (Nearsightedness)

Nearsighted people can see fine up close, but distant objects are a blur.

eye diseases-Myopia


Uncontrollable eye movements from nystagmus often have neurological causes.

eye diseases,Nystagmus

Ocular Hypertension

High eye pressure has no symptoms, but can be easily detected in an eye exam. Learn what can be done to prevent glaucoma and possible eye damage.

eye diseases-Ocular Hypertension

Ocular Migraine

Ocular migraine causes a sensation of looking through shattered glass. What’s happening

Ocular Rosacea

How to solve eye and eyelid irritation.

eye diseases Ocular Rosacea

Optic Neuritis and Optic Neuropathy

An inflamed optic nerve can cause blurry vision and blind spots.

https://www.rxharun.com/eye diseases Optic Neuritis


Peripheral Vision Loss

“Tunnel vision” can have various causes, including glaucoma.

eye disease Peripheral Vision Loss

Photophobia (Light Sensitivity)

Sensitive to light? Many eye conditions can cause this problem.

eye diseases, Photophobia


Pingueculae are growths on the eye. Are they serious?

eye diseases Pinguecula


All about this normal age-related loss of focusing ability that becomes noticeable after age 40. Also, read answers to frequently asked questions for a quick overview.

eye diseases Presbyopia


Pterygia, also called “surfer’s eye,” are growths on the eyeball that can interfere with vision.

eye diseases-Pterygium

Ptosis (Drooping Eyelid)

Drooping eyelids can be corrected with ptosis repair surgery, which tightens the muscle that supports the upper eyelid.

eye diseases Ptosis

Red Eyes

Red eyes can be caused by allergies, eye infections and eye injuries. Learn more causes of red eye and how to treat bloodshot eyes.

eye diseases Red Eyes

Retinitis Pigmentosa

Poor night vision and a narrowing field of vision beginning in childhood herald this rare disorder. Can vitamin A and beta-carotene help?

eye diseases Retinitis Pigmentosa

Sjogren’s Syndrome

Dry eye is a common symptom of this autoimmune disorder.

eye diseases-Sjogren's Syndrome

Sleep in Your Eyes

Do you often wake up with sticky, slimy, crusty “eye gunk”? This article explains where eye discharge comes from and when it’s cause for alarm.

eye diseases Sleep in Your Eyes

Snow Blindness

How to prevent a painful sunburned eye and temporary vision loss from UV exposure.

eye diseases, Snow Blindness

Stargardt’s Disease (STGD)

A form of macular degeneration that affects children and young people.

eye diseases-Stargardt's Disease


Key facts about strabismus and crossed eyes, including causes and treatments (strabismus surgery, vision therapy and orthoptics).

eye diseases ,Strabismus


What causes styes in your eyelid — and how to prevent them.

eye diseases, Stye

Stye Treatment – NEW!

How to get rid of a stye and keep them from coming back.

Subconjunctival Hemorrhage

Sudden redness in the white of your eye may be a subconjunctival hemorrhage.

Swollen Eyelids

Swollen eyes have many causes. Here are tips for prevention and treatment.

eye diseases, Swollen Eyelids


Painful inflammation of the uvea causes light sensitivity, floaters and blurred vision.

eye diseases, Uveitis

Vitrectomy & Vitreoretinal Procedures

These delicate surgical procedures for macular holes, retinal detachments and other conditions are performed in the eye’s deep interior.

eye diseases,Vitrectomy

Treatment of Eye Diseases


Many people with serious visual impairments can travel independently, using a wide range of tools and techniques. Orientation and mobility specialists are professionals who are specifically trained to teach people with visual impairments how to travel safely, confidently, and independently in the home and the community. These professionals can also help blind people to practice travelling on specific routes which they may use often, such as the route from one’s house to a convenience store. Becoming familiar with an environment or route can make it much easier for a blind person to navigate successfully.

Reading and magnification/ Eye glash uses

Most visually impaired people who are not totally blind read print, either of a regular size or enlarged by magnification devices. Many also read large-print, which is easier for them to read without such devices. A variety of magnifying glasses, some handheld, and some on desktops, can make reading easier for them.

Others read Braille (or the infrequently used Moon type), or rely on talking books and readers or reading machines, which convert printed text to speech or Braille. They use computers with special hardware such as scanners and refreshable Braille displays as well as software written specifically for the blind, such as optical character recognition applications and screen readers.

Some people access these materials through agencies for the blind, such as the National Library Service for the Blind and Physically Handicapped in the United States, the National Library for the

Computers and mobile technology

Access technology such as screen readers, screen magnifiers and refreshable Braille displays enable the blind to use mainstream computer applications and mobile phones. The availability of assistive technology is increasing, accompanied by concerted efforts to ensure the accessibility of information technology to all potential users, including the blind. Later versions of Microsoft Windows include an Accessibility Wizard & Magnifier for those with partial vision, and Microsoft Narrator, a simple screen reader. Linux distributions (as live CDs) for the blind include Vinux and Adriane Knoppix, the latter developed in part by Adriane Knopper who has a visual impairment. macOS and iOS also come with a built-in screen reader called VoiceOver, while Google TalkBack is built in to most Android devices.

Eye Diseases Treatment in Developing Country

A typical Snellen chart that is frequently used for visual acuity testing.

The definition of visual impairment is reduced vision not corrected by glasses or contact lenses. The World Health Organization uses the following classifications of visual impairment. When the vision in the better eye with best possible glasses correction is:

  • 20/30 to 20/60 : is considered mild vision loss, or near-normal vision
  • 20/70 to 20/160 : is considered moderate visual impairment, or moderate low vision
  • 20/200 to 20/400 : is considered severe visual impairment, or severe low vision
  • 20/500 to 20/1,000 : is considered profound visual impairment, or profound low vision
  • More than 20/1,000 : is considered near-total visual impairment, or near total blindness
  • No light perception : is considered total visual impairment, or total blindness

Blindness is defined by the World Health Organization as vision in a person’s best eye with best correction of less than 20/500 or a visual field of less than 10 degrees. This definition was set in 1972, and there is ongoing discussion as to whether it should be altered to officially include uncorrected refractive errors.

United Kingdom

Severely sight impaired

  • Defined as having central visual acuity of less than 3/60 with normal fields of vision, or gross visual field restriction.
  • Unable to see at 3 metres what the normally sighted person sees at 60 m.

Sight impaired

  • Able to see at 3 m, but not at 6 m, what the normally sighted person sees at 60 m
  • Less severe visual impairment is not captured by registration data, and its prevalence is difficult to quantify

Low vision

  • A visual acuity of less than 6/18 but greater than 3/60.
  • Not eligible to drive and may have difficulty recognising faces across a street, watching television, or choosing clean, unstained, co-ordinated clothing.

In the UK, the Certificate of Vision Impairment (CVI) is used to certify patients as severely sight impaired or sight impaired. The accompanying guidance for clinical staff states: “The National Assistance Act 1948 states that a person can be certified as severely sight impaired if they are “so blind as to be unable to perform any work for which eye sight is essential”. The test is whether a person cannot do any work for which eyesight is essential, not just his or her normal job or one particular job.”

In practice, the definition depends on individuals’ visual acuity and the extent to which their field of vision is restricted. The Department of Health identifies three groups of people who may be classified as severely visually impaired.

  1. Those below 3/60 (equivalent to 20/400 in US notation) Snellen (most people below 3/60 are severely sight impaired).
  2. Those better than 3/60 but below 6/60 Snellen (people who have a very contracted field of vision only).
  3. Those 6/60 Snellen or above (people in this group who have a contracted field of vision especially if the contraction is in the lower part of the field).

The Department of Health also state that a person is more likely to be classified as severely visually impaired if their eyesight has failed recently or if they are an older individual, both groups being perceived as less able to adapt to their vision loss.

United States

In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees (diameter) or less of visual field remaining, is considered legally blind or eligible for disability classification and possible inclusion in certain government sponsored programs.

In the United States, the terms partially sightedlow visionlegally blind and totally blind are used by schools, colleges, and other educational institutions to describe students with visual impairments.They are defined as follows:

  • Partially sighted indicates some type of visual problem, with a need of person to receive special education in some cases.
  • Low vision generally refers to a severe visual impairment, not necessarily limited to distance vision. Low vision applies to all individuals with sight who are unable to read the newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses. They use a combination of vision and other senses to learn, although they may require adaptations in lighting or the size of print, and, sometimes, Braille.
    • Myopic – unable to see distant objects clearly, commonly called near-sighted or short-sighted.
    • Hyperopic – unable to see close objects clearly, commonly called far-sighted or long-sighted.
  • Legally blind indicates that a person has less than 20/200 vision in the better eye after best correction (contact lenses or glasses), or a field of vision of less than 20 degrees in the better eye.
  • Totally blind students learn via Braille or other non-visual media.


Eye Diseases

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18 thoughts on “Eye Diseases; Causes, Types / Classification, Treatment”

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