- Behavioural Optometry
- Behavioural Optometry
- Accommodative Dysfunction
- Adult Behavioural Optometry
- Dry Eye & Blepharitis
- Convergence Excess
- Convergence Insufficiency
- Macular Degeneration & Glaucoma
- Myopia & Myopia Control
- Tracking Problems
- Vision Development
- Evidence Based Medicine
What is macular degeneration (MD)?
Macular degeneration (MD), also known as age-related maculopathy or senile macular degeneration, is damage or breakdown of the macula. The macula is a very small part of the retina, the light-sensitive tissue of the eye, which is responsible for central vision. This is the part of the retina that is used for the finest detailed vision.
How does MD affect vision?
MD damages the part of the retina responsible for central vision and for seeing fine detail, and makes it difficult to see small details of objects. Side vision is not affected. If both eyes are affected, reading and other tasks requiring fine vision may become very difficult, but because side vision remains, people with MD can usually take care of themselves.
What causes MD?
MD is the result of ageing processes in the eye. Some of the layers of the retina thicken and waste material which is usually removed from the retina forms deposits, distorting the retina. This distortion can cause damage to the other layers of the retina. In about 10 per cent of cases, new blood vessels grow into the macula from beneath. These newly-formed (neovascular) vessels are fragile and often leak blood into the retina, where the blood causes scar tissue to form. The scarring severely blocks central vision. Other forms of macular degeneration are inherited and not associated with ageing.
How common is MD?
Macular degeneration is the major cause of vision impairment and blindness in Australia for people over the age of 50. Early MD occurs in about 14 per cent of those aged 55 to 64 years, 18 per cent of those aged 65 to 74 years, and 30 per cent of those aged over 75 years. Men and women are equally affected. MD accounts for almost 50 per cent of legal blindness and up to 70 per cent of seriously impaired vision in people over the age of 70 years.
How is MD detected and diagnosed?
People with MD may notice that they can no longer read as quickly as previously even with their reading glasses, or they may notice that their vision has deteriorated. Many patients do not realise that they have a problem until their vision becomes blurred. Optometrists perform a number of tests in an examination, which enable them to detect the presence of MD in the early stages.
The optometrist examines the macula carefully with a range of specialised instruments such as an ophthalmoscope, retinal camera or slit-lamp with a high-powered lens. These instruments allow examination of the interior of the eye, including the macula. Sometimes the optometrist may place a drop in the eye to dilate the pupil to get a better view of the internal structures. Through the ophthalmoscope the optometrist will look for changes in the macula, such as accumulation of waste material or new blood vessels.
Another test that may be used is a grid pattern known as an Amsler chart. This is a regular grid that looks like a piece of graph paper. Patients with MD often report that sections of the grid appear to be distorted or missing.
Optometrists will usually refer patients whom they suspect have MD to an ophthalmologist (eye surgeon) for confirmation of the diagnosis. The ophthalmologist may perform a test called fluorescein angiography. In this test a fluorescent dye is injected into the patient’s bloodstream and the ophthalmologist observes the progress of the dye through the blood vessels in the retina. This reveals any leaking blood vessels.
Can MD be treated?
Recent advances in treatment of the early stages of neovascular MD involve injection of anti-VEGF (vascular endothelial growth factor) substances that prevent the formation and growth of abnormal blood vessels. This is the first treatment of MD that has been shown to improve vision in some cases but complete or permanent resolution of abnormal blood vessels is not possible. The treatment needs to be repeated as part of ongoing management of the disease. Associated risks of anti-VEGF treatment include formation of cataract and ocular inflammation.
Photodynamic therapy (PDT) is a well-established treatment for vascular forms of MD. Laser surgery may be used where new blood vessels have appeared in the macula area. A focused, intense beam of laser light is used to seal leaking blood vessels and prevent new vessels growing. This treatment is most effective when it is applied in the very early stages of the disease, before extensive damage has been done.
There is little that can be done to cure MD, particularly in its more advanced stages. One study found that antioxidant vitamin and mineral supplementation assisted in halting the progression of MD in a small percentage of patients. These supplements should be taken under the supervision of a health care professional as they may be associated with harmful effects.
People with MD can be helped to continue functioning normally. Many will eventually be classified as having low vision. Help in the form of low vision devices is available from optometrists and specialist low vision clinics. Low vision devices enable patients to make the most of their vision and include miniature telescopes, high-powered reading spectacles, hand-held and stand magnifiers, closed circuit televisions and other simpler aids such as large-print books.
What should you do about MD?
For treatment of MD to be effective, it must be diagnosed as early as possible. Regular eye examinations are the key to early detection of retinal changes and other signs of disease. If you notice any change in the quality of your vision, have your eyes examined immediately. Regular examinations are particularly important for people over the age of 50 years and people whose families have a history of eye problems. Other important preventative measures include minimising exposure to UV light and cigarette smoke, both of which are associated with MD. A low-fat diet rich in green leafy vegetables, nuts and fish may be beneficial in reducing the impact of MD.
What is glaucoma?
Glaucoma is a condition in which the nerve cells which transmit information from the eye to the brain become damaged. This prevents visual information from getting from the retina in the eye to the brain. Glaucoma is often associated with a build-up of pressure in the eye. The eye is filled with fluid which is constantly being replaced. If excessive amounts of fluid are produced, or if it cannot drain away properly, the pressure inside the eye can increase. In some forms of glaucoma, the pressure inside the eye can become extremely high, but in other forms the pressure may remain normal.
What causes glaucoma?
The exact causes of glaucoma are not known. In some cases the drainage network of the eye may not be formed properly, or may become blocked by natural materials or due to injury; in other cases there is no clear cause.
Is the damage that occurs in glaucoma serious?
If untreated, glaucoma can cause blindness. As the nerve cells are progressively damaged, the ability to see objects in different parts of the visual field is lost. The damage to the nerve cells cannot be reversed although it is often possible to prevent further damage. This damage can progress until only central vision is left or until the person is completely blind. The longer the disease is left untreated, the greater is the likelihood of damage. Modern examination techniques and treatment have made glaucoma a rare cause of blindness in Australia.
How can I tell if I have glaucoma?
Often you will not be aware that you have glaucoma until it is too late. Usually there are no symptoms until permanent damage has occurred. In some cases the increased pressure in the eye will cause blurred vision, apparent coloured rings around lights, loss of side vision, and pain and redness of the eye.
How does an optometrist diagnose glaucoma?
To diagnose glaucoma the optometrist looks at the nerve fibres at the back of the eye, examines the eye’s drainage network, measures the pressure in the eye with a special instrument called a tonometer and tests the field of vision. These tests are simple and painless.
How is glaucoma treated?
Eye drops and medicine are used to treat glaucoma initially. Surgery may be necessary if the blockage in the drainage system cannot be removed in other ways. Your optometrist will refer you to an eye specialist for treatment if they consider you have glaucoma.
Can glaucoma be prevented?
No. Early detection and treatment are the best way to control glaucoma.
Who is likely to be affected by glaucoma?
People over the age of 40 years are far more likely to have glaucoma than younger people. Also, glaucoma tends to run in families. People with a blood relative who has suffered from glaucoma and people over 40 years of age are at risk and should have their eyes checked regularly by an optometrist.