The most common cause of blindness is the cataract with the majority of cases in the Third World where corrective surgery is not available. In developed countries such as Australia, most vision loss is due to age related conditions that cannot be corrected.
Not everyone who is blind or vision impaired is the same. While some blind people have very little or no vision, most vision impaired people have some useful vision. Just because someone uses a white cane or a guide dog doesn’t necessarily mean they can’t see anything. The reason not all blind and vision impaired people have the same level of vision is because blindness and vision impairment can be caused by a number of different diseases and conditions, as well as accidents. The major categories are: inherited or congenital conditions, ageing, and conditions related to disease or infections.
There are many congenital eye conditions (those present at birth) which are either inherited or caused during pregnancy or birth by other means. Some of them may cause total and irreversible blindness while others may be treatable or may leave some vision remaining.
The underlying causes of vision loss, its severity and the limitations that it imposes vary from person to person. These include the following five conditions:
- Age Related Macular Degeneration (ARM)
- Diabetic retinopathy
- Retinitis Pigmentosa
This condition damages the macula. The macula is the central part of the retina and is responsible for reading and other tasks that require the detection of fine detail. People with macular degeneration have mostly peripheral vision and blurry or no central vision
Glaucoma is usually accompanied by high internal fluid pressure in the eye. This pressure can cause damage to the optic nerve which is responsible for carrying the images we see to the brain. Symptoms are subtle loss of contrast, difficult to drive at night, loss of peripheral vision, or loss of central vision.
It is a complication of diabetes and could lead to blindness. Diabetes can damage the capillaries of the retina, causing the retina to leak fluid onto the macula and making the retina swell, and blurring vision.
A cataract is a clouding of the eye’s lens, the part of the eye responsible for focusing light and producing clear, sharp images. Most cataracts are related to aging.
Retinal diseases characterized by progressive loss of visual field and night
blindness. The visual field loss often begins as a donut like ring in mid-periphery and eventually becomes “tunnel vision”.