Vision loss - some causes explained

There are many causes of vision loss. Some of the more common eye conditions include glaucoma, cataracts, age-related macular degeneration (AMD) and diabetic retinopathy.

Glaucoma
Glaucoma is the name given to a group of eye diseases that can cause progressive damage to the optic nerve (which transmits information from the eye to the brain) resulting in permanent vision loss. Early detection and treatment of glaucoma can prevent vision loss in most cases.

The eye produces a clear liquid (aqueous humour) to nourish the inside of the front of the eye. The amount of aqueous humour in the front chamber of the eye indicates the level of pressure in the eye (intraocular pressure). The intraocular pressure is regulated by the production and drainage of the aqueous humour through various drainage channels. Glaucoma is commonly, but not always, associated with increased intraocular pressure causing damage to the optic nerve.

Glaucoma is commonly referred to as the ‘sneaky blindness’ because vision loss is often subtle and is lost in the peripheral visual field. If the effects of glaucoma progress undetected vision loss continues into the centre of the visual field creating a tunnel vision effect. Vision loss can progress further to cause complete blindness.

Cataracts
Cataract is an eye condition which occurs when the lens of the eye becomes cloudy, blocking the passage of light to the retina (the inner layer of the back of the eye containing light sensitive cells for seeing). Vision gradually becomes blurred and problems with glare may occur as the cataract develops. Most cataracts occur as a result of the ageing process. A risk factor for cataracts is high UV light exposure. Some cataracts are also present at birth.

Surgery is the only effective treatment for cataracts. The cloudy lens is removed and replaced with a plastic lens implant.

Age-related macular degeneration (AMD)
This is one of the leading causes of vision loss in Australia among older people. AMD causes the deterioration of the central vision – the area of most acute vision. Central vision is used to see the fine detail such as reading, writing, watching television and recognising faces. Central vision is distorted or affected, though peripheral (side) vision usually remains normal as long as the individual does not have other eye conditions affecting their vision.

There are two forms of AMD, dry and wet. There is no effective treatment at the moment for dry AMD. Wet AMD is where abnormal blood vessels grow in the retina that can leak fluid or bleed which can eventually damage the macula, which is responsible for central vision. For wet AMD, although there is no cure as yet, there is treatment available to try and stabilise the condition and reduce severe vision loss.

Diabetic retinopathy
Diabetic retinopathy is an eye condition that can result as a complication of diabetes. Increased blood sugar levels can damage the blood vessels in the retina (back of the eye). If the diabetic retinopathy is not treated it can cause vision loss or blindness.

If you have diabetes or have a family history of diabetes, have your eyes checked regularly by an eye care practitioner (optometrist or ophthalmologist).

Where to get help

• Your doctor
• Optometrist or ophthalmologist
• Vision Australia Tel. 1300 84 74 66

• AMD causes loss of fine vision and can affect reading and writing.
• People with diabetes should have their eyes checked regularly.
• Most cataracts occur as a result of the ageing process and can only effectively be treated by surgery.

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