Low Vision

A person is said to have low vision when their eyesight is limited or impaired and cannot be corrected with conventional glasses or contact lenses

Low vision can affect people of all ages and can have an impact on many aspects of a person’s life, upsetting their ability to carry out many of the daily tasks for which vision is essential, such as recognising faces, reading the newspaper, dialling the telephone or seeing road signs.  Fortunately, with the help of magnifiers and other vision aids, the remaining vision can often be used effectively.

In our practices our optometrists can help people with vision impairment to make the best use of their remaining vision.  We keep a large selection of Low Vision aids at our Hume Street practice and we are affiliated with the Guide Dogs Queensland – Toowoomba Low Vision Clinic, where Geoff Somerville volunteers his time as a consultant.

There are many different causes of low vision including:

  • Macular Degeneration
  • Glaucoma
  • Diabetic Retinopathy

Age-related macular degeneration (AMD) affects 25 to 30 million people worldwide.  The macula, located in the centre of the retina, processes the sharp details of images creating our central vision.  As our eyes get older, the membrane separating the macula from retinal blood vessels can weaken, depriving the macula of nourishment.  Without nourishment the macula degenerates, and so too does our central vision.

AMD can seriously affect the vision in just a few months or over the course of several years. In severe cases, scar tissue from leaky blood vessels causes irreversible blind spots, however it is important to note that AMD will never cause total blindness since peripheral vision remains unaffected.  The cause and cure for AMD are unknown. However, treatments are available in a small percentage of cases. Possible risk factors include smoking, genetics, hypertension, sun exposure, far-sightedness, light skin or eye colour, and poor diet.

Glaucoma causes the gradual loss of peripheral, or side, vision. Although linked to older age, glaucoma may develop at any age, even infancy.

The cause of glaucoma is unknown, but it is important to be aware of the possibility of glaucoma, particularly if you have any of the risk factors, including age, heredity, myopia (near-sightedness), increased intraocular pressure (IOP), and systemic disease such as diabetes and hypertension.  Some prescription medications such as as cortisone (steroid) drops, have also been linked to glaucoma.

Vision loss from glaucoma is caused by diminishing nerve function from increased IOP and other influences on the optic nerve, resulting in painless loss of peripheral vision.  In the vast majority of cases, especially in the early stages, there are few signs or symptoms. In the later stages of the disease, symptoms include loss of side vision, an inability to adjust the eyes to darkened rooms, difficulty in focusing on close work, rainbow coloured rings around lights and frequent changes of prescription glasses.

Diabetic retinopathy is present in 90% of those who have had diabetes for more than 20 years and the chances of having some form of diabetic retinopathy increases the longer a person has had diabetes.  In the early stages of diabetic retinopathy, small blood vessels weaken and leak fluid or tiny amounts of blood which distort the retina.  When this happens, normal or blurred or changing vision may be experienced.  Many people with diabetes have some degree of retinopathy, however most cases do not progress to more severe problems.

In a more advanced stage, blood vessels in the retina are blocked or closed completely, and areas of the retina die. Fortunately, proliferative diabetes occurs only in a small minority of people and arises when new, abnormal blood vessels grow to replace old ones. Severe visual loss or blindness can result if the new fragile vessels or scar tissue ruptures and bleeds or tears the retina.

 

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