The antioxidant vitamins C and E

Age-Related Macular Degeneration (AMD)
AMD is characterized by a progressive loss of photoreceptors and degradation of the
macula, leading to a progressive loss of central and sharp vision. As in most ocular tissues,
the retina and the macular area in particular are severely exposed to oxidative
stress due to the high consumption of oxygen and cumulative exposure to sunlight.
The presence of photosensitizers and a high content of polyunsaturated fatty acids
(PUFA) contribute to the susceptibility to photooxidative damage (32). The retina also
contains high amounts of vitamin E, protecting against retinal oxidative damage, and
vitamin E deficiency results in retinal degeneration, accumulation of lipofuscin in the
retinal pigment epithelium, and loss of PUFA (33). Early experimental studies demonstrated
protective (antioxidative) effects of vitamin E in eye tissues (34), leading to the
suggestion that vitamin E may counteract degenerative processes in the retina. Data
from animal studies, however, are lacking.
In epidemiologic studies, it was observed that AMD patients have significantly
lower blood vitamin E levels than control subjects; moreover, vitamin E levels are
inversely correlated with the severity of AMD (35). The Pathologies Oculaires Liées à
l’Age (POLA) survey, a prospective, population-based study on risk factors for AMD
and cataract (n = 2584 participants) reported an 82% risk reduction of AMD in the
highest vs. the lowest quintile of lipid-standardized blood vitamin E levels, and an
inverse association with early signs of AMD (36). In the Beaver Dam Eye Study, an
increased risk of AMD with low intake of vitamin E was observed (37) .
Clinical Trials
The role of vitamin E in the prevention of age-related eye diseases has yet to be investigated
in clinical trials. A first large-scale intervention trial on the effects of vitamin E
supplementation (500 IU/d) on the risk of AMD or cataract, the Vitamin E and
Cataract Prevention Study (VECAT) with 1205 participants, has just been completed.
However, the results of the VECAT study have not yet been reported (38).
A few clinical trials have been published providing data on the effects of mixtures
of antioxidants on age-related eye diseases. The Alpha-Tocopherol Beta
Carotene (ATBC) study with middle-aged male Finnish smokers reported that daily
supplementation with vitamin E (50 mg) and β-carotene (20 mg) for 5–8 y did not
affect incidences of cataract surgeries (39) or AMD (40). In contrast, two recently
completed clinical trials reported a benefit from antioxidant supplements on either
cataract or AMD. The Roche European American Cataract Trial (REACT) with 297
adults from the United States and the United Kingdom was a 3-y controlled trial on
the effects of antioxidant supplementation (600 IU vitamin E, 750 mg vitamin C, and
18 mg β-carotene per day) on cataract progression in patients with early cataract (41).
The results show a significantly reduced progression of cataract in participants from
the United States; however, in the UK cohort, the effect was not significant. The
AREDS study on antioxidant vitamins and AMD (trial part one) or cataract (trial part
two) is an ongoing multicenter trial (n = 4757 participants) with elderly AMD
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