Blindness

Overview of blindness

The World Health Organisation (WHO) has estimated that around 39 million people all over the world are blind and 246 have poor vision. The statistics of WHO have also shown that India has the highest blind population in the world. A recent report published in the Times of India has shown that India loses around 37 billion dollars due to eye-sight problems. So evidently, the burden of eye-sight problems in India as well as in the world is very high and needs to be resolved on an emergency basis.

What is blindness?

Blindness is defined as the partial or complete loss of vision. This is precipitated by different physical and environmental factors. Existing diseases of the eye may worsen and lead to blindness in many cases. This article will discuss some of the conditions that can give rise to blindness.

Cataract

Cataract is defined as a type of vision impairment characterized by unusual blurring the eye lens causing gradual opacity of lenses and loss of clear vision.

The general causes of cataracts are as follows-

• Prolonged and unprotected exposure to Ultraviolet radiation
• Trauma due to past incidents of eye-infection or eye injury
• Certain drugs such as corticosteroids and diuretics
• After-effects of previous diseases like diabetes, eczema (skin disorder), uveitis (eye inflammation), high blood pressure, glaucoma (disease of the eye)
• Continuous exposure to toxic chemicals present in the environment
• Addictive habits like smoking and alcohol consumption
• Prolonged use of vitamin supplements (hypervitaminosis symptoms)
• Diet rich in fat and deficient in anti-oxidant vitamins

What are the main signs and symptoms of cataracts?

The warning signs of cataracts are as follows-

• Impaired vision accompanied by cloudiness or fogginess
• A gradual opacity of the pupil causing loss of clear vision
• Hypersensitivity to bright light (increased glare)
• Short-sightedness (Myopia) characterized by difficulties in distance-vision
• Double vision conditions where multiple images are perceived in one eye (diplopia)
• Difficulty recognizing color (can lead to color-blindness)
• Poor vision in bright sunlight
• Poor night vision, occasionally leading to permanent night-blindness
• Frequent change in prescriptions related to eye-glasses
• Trouble performing mundane activities like reading, recognizing people or objects, driving, watching television and walking

What are the different types of cataracts?

According to morphology, cataracts are of three types-

• Nuclear Sclerotic Cataracts
• Cortical cataracts
• Posterior sub-capsular cataracts

According to aetiology, cataracts are of four types-

• Degenerative cataract
• Congenital cataract
• Traumatic cataract
• Secondary cataracts

Macular Degeneration

Macular degeneration (MD) is the slow and painless breakdown of the eye’s macula. The macula is the central part of the retina and is predominantly made of cone cells which are the visual cells. Degeneration of the macula occurs due to loss of visual cells, cone cells, and rods cells, and thus, causes blurry vision or eventual blindness. In some rare cases, blindness can be abrupt. Since the macula degenerates overage, the disease is termed as Age-Related Macular Degeneration. If the disease is found to have a genetic linkage, it is known as juvenile macular degeneration or congenital macular degeneration. In the latter case, macular degeneration is an autosomal recessive eye disease.

What causes Macular Degeneration?

Macular degeneration is precipitated by a number of catalyzing factors. These are listed below-

• Age: The risk of being affected by AMD increases with age.
• Smoking: Smokers have to endure severe vision loss when compared to non-smokers.
• Heredity: People with close relatives affected by AMD are likely to develop AMD with age.
• Sunlight: Laboratory studies show that exposure to sunlight can affect the retinas.
• Diet: Obesity, intake of artificial fats and high cholesterol can increase the risk of being diagnosed with AMD.
• Race: AMD is largely observed in whites but it can affect other races as well.
• Drugs: Certain drugs namely, Aralen and phenothiazine can cause macular degeneration.
• Gender: Women are more likely to be affected by AMD.

Other general factors include-

• Inheritance of a faulty gene (usually dominant) from one parent
• Inheritance of a defective gene (usually recessive) from both parents
• Death of macular cells
• Abnormal growth and rupture of blood vessels within the macula

What are the signs and symptoms?

The common symptoms of macular degeneration are as follows-

• Partial or complete loss of central vision
• Gradual loss of color vision
• Photosensitivity (aversion to extremely bright light)
• Loss of night vision
• Difficulty reading the blackboard in school
• Defective perception of straight lines as curved or bent
• The appearance of dark spots in the central field of vision
• Problems in distinguishing minute details
• Difficulty performing tasks such as threading a needle, reading very small prints or reading street signs

What are the types of macular degeneration?

There are two main types-

• Dry MD: This is caused by thinning of the RPE, Retinal Pigment Epithelial cells.
• Wet MD: This is caused by thickening of the membrane underlying the retina which eventually breaks.

Glaucoma

Glaucoma is a type of eye disease that occurs due to damage and death of the optic nerve. In a majority of the cases, glaucoma results from an abnormal elevation in the intraocular pressure. Faulty drainage within the eye chambers also contributes to glaucoma in many patients. Serious cases of glaucoma lead to vision disturbance and blindness.

Causes of glaucoma

These are-

• Blockage of the drainage channels of the eye, which obstructs the drainage of the intraocular fluid
• Increase in intraocular pressure due to build up of fluids inside the eye
• Damage of the sensory optic nerve due to high pressure
• Gradual hollowing of the optic disc that forces the sensitive optic nerve fibres into a curved shape

What are the types of glaucoma?

Two primary types of glaucoma have been identified so far. These are-

• Open angle glaucoma: It occurs due to progressive clogging of the drainage paths in the eye chamber, which leads to an increased intraocular pressure.
• Closed angle glaucoma: Here, the gap between the cornea and the iris is shortened, which causes an obstruction in fluid flow.

Warning signs

These are given below-

• Partial or complete loss of peripheral vision
• Loss of central vision (in the late stage)
• Appearance of multicoloured (typically rainbow coloured) circles around bright lights
• Pain in the head and eyes
• Blurred vision
• Nausea and vomiting
• Dizziness

Diagnosis and treatment for blindness

The following diagnostic tests may be beneficial-

• Visual acuity test
• Visual field test
• Dilated eye exam
• Tonometry
• Pachymetry

Blindness in most cases is irreversible. In some cases however, surgical treatments may help restore vision.

Treatment & Prevention

Treatment of visual impairment and blindness often includes:

• If the blindness is due to nutritional deficiency, it can be addressed by bringing the required dietary changes.
• Cataract-induced blindness can be treated by cataract surgery. This restores visions in a majority of cases.
• If the cause of the blindness is an inflammation and/or infection, medications can help in reducing and controlling the symptoms. These could be taken orally or in the form of drops.
• If a scar in the cornea has caused blindness, cornea transplant surgery might help.
• However, there are certain cases such as stroke-induced optic nerve damage or chronic retinal detachment, where the vision loss is irreversible.

Prevention of blindness can be done by:

• Ensure that your diet doesn’t lack in basic nutrients such as vitamin A which are vital for developing normal eyesight.
• Early detection and treatment of glaucoma can also help prevent partial or complete vision loss.
• Monitor your blood sugar levels. Diabetes is one of the leading causes of vision loss (diabetic retinopathy). This can be checked by getting proper treatment for diabetes, having a regular exercise routine, and maintaining a healthy weight.
• Go for regular eye check-ups. This is more important for the aging population.
• If your lifestyle and/or your occupation expose you to toxic fumes, high-temperature flames, eye irritants etc make sure that you protect your eyes from these.
• Be careful about eye injuries. In case of any accidental or unintentional eye injury happens, don’t treat it lightly. Seek immediate medical attention.

References