Blindness and Vision Impairment

Universally, at least a billion or more people suffer from different forms of vision impairment globally. This is not to mention cases that are yet to be addressed.

Vision impairment and blindness affects people of all ages but is more dominant in old age. However, it is notable that most of the leading causes of blindness and vision impairment are preventable and can be treated.

What is the difference between blindness and vision impairment?

Blindness is the state of complete loss of vision, due to either illnesses or genetic conditions. Vision impairment refers to the decrease of visual ability to a certain degree that results in problems that cannot be fixed by corrective methods such as glasses or corrective surgery. There are different categories of vision Impairment and blindness. 

Older woman's eyes are being tested | © WHO

An old woman having her eyes being tested (Photo: WHO)

Types of vision impairment

Distance vision impairment

People who have this type of vision impairment can be referred to as long-sighted. The distance of an object from the eye appears farther than it is. Most people who are affected cannot see with ease something that is too far from the eye. Distance vision impairment occurs when the distance from the front to the back of the cornea is too steep.

Near vision impairment

Also termed as short-sightedness, this type of vision impairment causes one not to see objects that are far more clearly. Objects appear blurry at a distant and clearer when closer to the eye. That means that light does not focus on the light-sensitive tissue at the back of the eye; it focuses only on the front. 

Types of blindness

Total Blindness

Total blindness is when a person has a complete lack of vision. Total blindness can occur naturally as some are born without vision, but other factors cause it in some cases. 

Legal Blindness

When someone is termed legally blind, it means that they have a corrected vision of 20-200 in their best-seeing eye or less in one eye. This means that if an object is 200 meters away, you would have to stand at least 20 meters close to see it. People with a normal vision can see the same object without moving closer. 

Partial Blindness

When someone is partially blind, it means they have specific limited vision. Partially blind people may see blurry objects or have difficulties distinguishing shapes of objects. With that behind us, let’s address a frequently asked question. What are the leading causes of blindness and vision impairment?

Leading causes of blindness and vision impairment

Blindness and vision problems can occur suddenly or over time due to various causes, from illnesses, genetic problems or accidents. Interestingly, when blindness occurs naturally like in old age, there is no pain, at least most of the time.

In a nutshell, blindness and vision impairment can be attributed to a wide range of causes. However, cataracts and uncorrected refractive errors are the primary causes of sight loss. Age-related macular degeneration and glaucoma follow closely as the next most prevalent contributors to sight loss. Here we are going to look at six distinct causes.

  1. Uncorrected Refracted Errors

    Uncorrected Refractive Errors is one of the leading causes of blindness and occurs when refractive errors are not corrected or treated on time. Refractive errors include: Myopia (near-sightedness), hyperopia (far-sightedness), astigmatism (distorted vision), presbyopia (inability to focus up close, need to hold reading materials farther from the eyes) Luckily, optician-prescribed spectacles can help manage refractive errors.

  2. Glaucoma

    Glaucoma is caused by a build-up of fluid and damage in the optic nerve. The optic nerve connects eye muscles to the brain and gets damaged by too much eye pressure. This condition affects mostly older persons from the age of sixty. Different types of glaucoma can be detected through a tonometry test which measures intraocular pressure. Glaucoma is only treatable in early stages as the damages can be irreversible.

  3. Cataracts

    A cataract is a clouding in the lens of the eyes which leads to a decrease in vision. Cataracts are caused by ageing, radiation exposure and diabetes in severe cases. They occur when the lens of your eyes becomes less transparent, causing eyesight to be cloudy. The clouding is as a result of protein building up in the lens. Symptoms may also include seeing faded colours, trouble with too much light and night blindness. It is easy to diagnose cataracts, and surgery is the most effective treatment for the condition. A clear, artificial lens can also replace the cloudy eye lens through a safe, out-patient procedure.

  4. Diabetic Retinopathy

    Retinopathy is a diabetes complication that affects the eyes. It is caused by damage to the tissue at the back of the eye, due to poorly controlled blood sugar. High glucose levels cause damage to the blood vessels in the retina. Symptoms include pain in the eyes, dark areas of vision or blurry vision that gets worse with time. If detected early through screening, the condition is likely to be prevented by diabetes management. Advanced cases can be treated with surgery or laser treatment.

  5. Age-Related Macular Degeneration

    Age-related Macular degeneration is an eye disease that occurs when the small central portion of your retina, called the macula, wears down and loses function. Dry macular degeneration causes loss in the centre field of vision, while wet macular causes leaky blood vessels to grow under the retina. While it is painless, you may start to lose central vision. Age-related macular degeneration has no permanent cure because of the age factor. However, early detection can aid in managing the condition with simple adjustments like prescribed spectacles. A particular combination of vitamins and minerals can help to slow down the progression of the macular degeneration.

  6. Trachoma

    A girl drinks from a dosing cup  | © Gates Archive/Dominique Catton

    This is a bacterial infection caused by bacterium Chlamydia trachomatis and affects the eyes. The infection causes the inner surface of the eyelids to be rough. The roughening in the eyelids causes pain in the eye and a breakdown on the cornea's outer surface. The pressure in the eye eventually leads to total blindness. Trachoma is the leading preventable cause of blindness in the world and is very contagious. Symptoms begin with mild itching and irritation in the eyes and eyelids, then progress to eye pain and blurry vision. Early stages are treatable with antibiotics. Advanced stages of trachoma are treated with surgery. Proper sanitation and clean water play a vital role in the prevention of trachoma infections.