Age-related macular degeneration and its possible prevention

In reply: While the published literature on dietary supplementation with the antioxidants lutein and zeaxanthin is highly encouraging, it does not yet pass the requisite standards for public endorsement provided by large-scale, independent, evidence-based medical trials. The controlled (“LAST”) trial of lutein1 cited by Cohen consisted of just 91 patients divided into three subgroups including the placebo group, who were followed for only 1 year. The measurement of visual improvement on a Snellen chart would not be accepted as “gold standard” evidence by major granting agencies and regulatory affairs bodies, who demand the higher discrimination of a logarithmic visual acuity chart. Moreover, the data were not derived from multicentre trials and independently assessed.

It is instructive to compare the methodology of the LAST trial with that of the ARED Study,2 which involved 11 centres, 3640 patients and an average follow-up of 6.3 years. For these reasons, although I mentioned lutein in an encouraging fashion, I did not endorse it to the same extent as vitamin C, vitamin E and zinc supplements.

The other reasons for giving limited recommendation of antioxidant supplements at this stage relate to the fact that it is not yet clear to what extent supplements would be beneficial over and above a diet targeted to provide these antioxidants in plentiful supply. It may yet be shown that a nutritious diet — with emphasis on brightly coloured and leafy vegetables, fresh fruits, nuts and fish, coupled with reduced processed vegetable oils (except olive oil) — can, alone, provide substantial protection. While the supplements are generally deemed to be safe, they are not without occasional serious side-effects and have not been followed long term.

Richer, one of the authors of the lutein study, 1 acknowledges commercial relationships with the supplement suppliers, and states that the study requires greater numbers and long-term follow-up to be confirmed.

Cohen cited a second article3 that refers to a 2-year study of cataract, in which a mere 17 patients were allocated to three subgroups including the placebo group. It is not usual practice to quote conclusions from such a small, and therefore potentially unreliable, trial design.

Cohen is right to point to lutein and possibly zeaxanthin supplements as an encouraging possibility for preventing blindness from macular degeneration, and I hope the evident enthusiasm and rapid marketing of lutein proves justified in the long run by forthcoming major trials.