Macular degeneration

Different parts of the retina perform different visual tasks. For example, the peripheral retina is useful for night vision and detecting movement and motion. The central part of the retina, the macula, is needed for fine visual tasks such as reading, writing, threading a needle, and tying fishing flies etc. In macular degeneration, degenerative processes occur which impede central vision.

Age related macular degeneration (AMD)

Age related macular degeneration is a common cause of visual impairment in adult New Zealanders.

The symptoms relate to degenerative processes that are occurring at the macula and can affect both eyes.

The macula

Normal eye Macular degeneration

The macula is that part of the retina that we use for fine visual tasks. The retina is a layer inside the eye on which light is focussed by the cornea and lens. It is rather like a film of a camera in that it responds to a focussed light and transmits signals to the brain enabling us 'to see'.

Different parts of the retina perform different visual tasks. For example, the peripheral retina is useful for night vision and detecting movement and motion. The central part of the retina, the macula, is needed for fine visual tasks such as reading, writing,
threading a needle, and tying fishing flies etc.

In macular degeneration, degenerative processes occur which impede central vision.

Types of macular degeneration

There are many categories of macular degeneration and these sub-divisions can be based on appearance, age at onset, etc. One common classification includes a subdivision of wet or dry appearance to the macula.

In early forms of macular degeneration, accumulations of waste products can be seen underneath the retina. These deposits are called drusen and can be either of small discreet types or larger confluent disturbances. Progression of this stage can be heralded by abnormalities in pigmentation or thinning of the retina. If the disease process progresses, then these changes can become more marked and can be associated with complications of macular degeneration.

Complications of macular degeneration

The thinning of the macula can become more widespread with time and lead to features of atrophic macular degeneration. This typically is a slow process with affected people becoming symptomatic in their eighties. Some patients with advanced macular degeneration can develop a more exudative reaction where there is leakage of fluid or development of abnormal blood vessels beneath the macula. This process tends to be faster and occurs at a younger age group than atrophic changes.

Prevention and therapy

There is no proven treatment or life-style change which has been shown to prevent macular degeneration. However, high blood pressure and smoking are known to increase the risk of visual loss from macular degeneration. Equally controlling high blood pressure and stopping smoking dramatically decreases that risk.

The National Eye Institute has also shown for patients with moderate or advanced forms of macular degeneration a combination of vitamins and anti-oxidants can be beneficial. In New Zealand this formulation is not funded by Pharmac and before starting treatment it is advisable to have a thorough eye examination, including photographs of the macula, to ensure the medication is going to be of benefit.

Retinal laser surgery for patients with exudative complications of macular degeneration was the treatment of choice up until quite recently. However the development of a class of drugs that can act on the abnormal leaking vessels in the eye has lead to a widespread change in practice. These drugs, such as Avastin and Lucentis are injected into the vitreous cavity within the eye and allow for better visual outcomes compared with most forms of laser treatments. Regular retinal scans (OCT) are required to monitor the effect of the treatment and repeat injections are often required to reduce the leaking vessels causing the reduction in vision.

Visual aids

Patients who lose or have defective reading vision can be helped with low visual aids such as magnifiers or closed circuit television. If the central vision is totally lost, talking books can replace the written word. More sophisticated aids with computers and talking typewriters can enable patients who lose central vision to continue to lead a normal life and occupation.

Test your eyes with the Amlser grid

• Use a bright reading light
• Wear your reading glasses if appropriate
• Sit approximately 40 cm back from the screen
• Cover one eye
• Note irregularities (wavy, size, grey, fuzzy)
• Look at centre dot
• Repeat the test with your other eye
• Contact ophthalmologist if you see any irregularities or notice any changes

Amsler Grid

Amsler grid viewed with macular degeneration

Future developments for treatment

Treatment and techniques to reduce macular degeneration will be increasingly important as it is a major cause of visual impairment in the developed world, including New Zealand. With the current promising research there may well be better treatments available for the prevention of macular degeneration in the future.

Auckland Eye is an affiliated provider to Southern Cross Healthcare for OCT measurements

For more information on macular degeneration please contact our friendly specialist team