Macular Degeneration

Macular degeneration is an important disease affecting over 25% of the Canadian population above the age of 80. It is the most common cause of registerable blindness in the senior population in North America and the incidence is increasing.

There have been two medically controllable risk factors identified:

1. Smoking
2. Hypertension

There are treatments for subretinal neovascularization which are quite well recognized and have been available for a number of years:

1. Direct photocoagulation of extrafoveal nets.
2. Ultraviolet photoactivated dye Verteporfin (Visudyne).

The results of these are helpful, but treatment is characterized by high recurrence rates and the need for recurrent assessments and treatments.

The AREDS (Age Related Eye Disease Study) trial was an effort by the National Institute of Health to look at high dose antioxidants, vitamins and age related ocular disease. Use of these agents showed no effect on development of age related cataract. However, a 25% protection from vision loss due to macular degeneration was conferred on the group taking daily the following combination of antioxidants and zinc:

• Vitamin C 500 mg.
• Vitamin E 400 IU
• Betacarotene 15 mg.
• Zinc 80 mg.

This is Level 1 evidence and a represents a major advance in the management of this disease. There are many claims made for a variety of medications but it seems to be important that agents and doses taken, be the same as those of the trial.

Smoking, of course, is a controllable risk feature, but the ingestion of betacarotene with cigarette smoking does increase the risk of lung cancer.

This treatment does not work in all eyes. Patients with minimal, i.e. less than -6 small drusen or central geographic atrophy, do not seem to be helped.

"those with extensive intermediate sized drusen, at least one large drusen, non-central geographic atrophy in one or both eyes, advanced AMD or vision loss due to AMD in one eye without contraindications such as smoking should consider taking a supplement of antioxidants plus zinc such as used in this study".

From a primary practice point of view it would be helpful to ascertain that patients on ocular antioxidants are, in fact, receiving the correct dose, have considered smoking cessation and are in optimum antihypertensive control.

- John Hamilton

Thanks to Dr. Raj Mohandas for reviewing the draft copy of this article. Dr. Mohandas is a consultant Ophthalmologist at St. Martha's Regional Hospital, Antigonish, Nova Scotia.

1. AREDS Age related Eye Disease Study Research Group, Archives of Ophthalmology 2001 October; 119(10):1417-36