Types of Visual Impairment

Researchers estimate that 575,000 people in Australia have a visual impairment with 66,000 being blind. Of these estimates, 70% of them are over the age of 65.

Defining Blindness

A person is legally blind if they can’t see beyond six metres in front of them. A person with normal vision can see up to 60 metres in front of them. You’re also considered legally blind if your field of vision is 20 degrees in diameter or less. The Australian Government uses the terminology “legally blind” to classify a person who has sight loss to the degree that entitles them to special benefits.

A person can have low vision if they have a form of permanent vision loss that they can’t correct with glasses. It’s severe enough to interfere with their daily functioning ability. Low vision is common in people of all ages. Anyone with low vision may have trouble reading a magazine or newspaper, recognising faces, seeing road signs or dialling the telephone.

Common Types of Blindness

Several types of blindness affect people of all ages in Australia. They include but are not limited to:

• Macular Degeneration (Age-Related)– This is severe vision impairment for people over 40. You experience distorted vision, sudden decline in the ability to see things clearly, dimmed colour vision and hallucinations.
• Cataracts – Cataracts cloud the lens of your eye. Symptoms include hazy vision, blurring, halos, double vision, and feeling like you’re looking through a curtain.
• Diabetic Retinopathy – Diabetes can damage the small blood vessels in the eye, and this causes bleeding or swelling. It can cause distorted or blurred vision.
• Glaucoma – Glaucoma is a genetic eye disease that causes fluid buildup in the eye. Blurred vision, difficulty adjusting to low light, tunnel vision and blindness are possible without early correction.
• Optical Atrophy – Degeneration or damage to the optic nerve causes optic atrophy. This condition is untreatable, and it has varying severity levels.
• Stargardt’s Disease – This is a form of macular degeneration that occurs before age 20. Blurred vision, vision loss, centralised blind spot and a reduced ability to see colours are common.
• Stroke – A stroke causes a restriction of oxygen to the brain. A stroke can interfere with the field of vision, visual perception, visual acuity and eye muscles. These vision changes may be temporary or permanent.

Causes of Blindness

In Australia, as well as other developed nations, the leading blindness causes include macular degeneration, diabetes complications, traumatic injuries and glaucoma. In third-world countries, the main causes of blindness include glaucoma, cataracts, injuries and the inability to get corrective lenses.

Infectious causes of blindness in poor areas include onchocerciasis (river blindness), trachoma and leprosy. Developed nations have infectious causes of blindness too, and the most common cause is herpes simplex. A vitamin A deficiency, blood vessel diseases, stroke, retinopathy of prematurity, ocular inflammatory diseases, congenital abnormalities, primary or secondary malignancies of your eye, chemical poisoning and hereditary diseases can all cause visual impairment.

Blindness Risk Factors

Blindness risk factors include poor prenatal care, advancing age, premature birth, failure to wear safety glasses, poor nutrition, smoking, poor hygiene, ocular diseases and hereditary factors. Medical conditions can contribute to your blindness risk factor. People who have hypertension, diabetes mellitus, cardiovascular disease or cerebrovascular disease are at higher risks.

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