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Introduction
Cataract incidence increases with age, reduces visual performance, and is responsible for about 30-50 million cases of blindness worldwide, according to the authors of a study published this month (1). Since oxidative damage is thought to play a role in initiating and promoting cataract, antioxidant nutrients may be of benefit by reducing oxidative stress in the lens. Observational studies have linked higher intake of vitamin E and lutein, as well as long-term vitamin C supplementation, with lower risk of cataracts (2-4).

Intervention trials with high-dose beta-carotene, along with vitamins C and E have produced mixed results (5,6). In contrast to beta-carotene, lutein and its isomer, zeaxanthin, are the only carotenoids detected in lens and macula. Therefore, an association between these carotenoids and cataract is biologically plausible. The aim of this study was to assess the effect of high-dose vitamin E and lutein in senile cataract.

Methods:

In this double-blind trial, seventeen volunteers with mostly posterior subcapsular and nuclear opacities, were randomized to receive one of three treatments: a) 15 mg lutein capsule (as esters, equivalent to about 7 mg free lutein); b) 100 IU vitamin E capsule OR c) placebo capsule (corn oil). The supplements were taken three times weekly. Average supplementation time was 26 months (range of 12-36 months). Visual function, tested every three months, was measured with routine static (visual acuity) and several dynamic (glare sensitivity) clinical diagnostic tests. Visual acuity at baseline was within the same range for all groups, but placebo-treated subjects showed lower levels compared to subjects in the lutein group.

Results:

Compliance was greater than 80%. Some subjects dropped out during the 3-year study, mainly in the placebo group, to undergo cataract surgery. Therefore only data from the first 24 months were used for statistical analysis. Both visual acuity and glare sensitivity improved in the lutein group, with visual acuity significantly improved over baseline (p<.005). A trend toward maintenance of visual acuity was seen in the vitamin E group, while it tended to decrease in placebo takers. Clinical examination showed that cataracts did not progress in four of five patients in the lutein group, three of five in the vitamin E group, and one of five among placebo subjects.

Figure 1. Changes in visual acuity of patients with cataracts during the supplementation study (eyes were assessed individually). Lutein group (n = 9), a-tocopherol group (n = 10), and placebo group (n = 7). CI = confidence interval.

Comments

According to the researchers, this pilot study suggests that increasing lutein intake though lutein-rich foods or supplements improves the visual performance of patients with age-related cataract. Interesting, the serum levels of lutein achieved in this study were very close to those associated with substantial increases in macular pigment density seen in other trials. These results call for larger studies to confirm the benefits of lutein in patients with cataract.

References

1. Olmedilla B et al. Lutein, but not alpha tocopherol, supplementation improves visual function in patients with age-related cataracts: A 2 year double-blind, placebo controlled pilot study. Nutrition 19:21-24, 2003
2. Taylor A et al. Long-term intake of vitamins and carotenoids and odds of early age-relate cortical and posterior subcapsular lens opacities. Am J Clin Nutr; 75:540-49, 2002
3. Lyle BJ et al. Serum carotenoids and tocopherols and incidence of age-related cataract. Am J Clin Nutr; 69:272-7, 1999
4. Chasan-Taber et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am J Clin Nutr; 70:431-2, 1999
5. The REACT Group. The Roche European American Cataract Trial (REACT): A randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract. Ophthalmic Epidemiology; 9:49-80, Feb. 2002
6. AREDS report no. 9. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E and beta carotene for age-related cataract and vision loss. Arch Ophthalmol 119(10):1439-52, 2001.