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Editors Selection IGR 13-2

Medical Treatment: Dietary supplements

Comment by Keith Martin on:

60189 A two-year follow-up of oral antioxidant supplementation in primary open-angle glaucoma: an open-label, randomized, controlled trial, Garcia-Medina JJ; Garcia-Medina M; Garrido-Fernandez P et al., Acta Ophthalmologica, 2015; 93: 546-554

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Mixed supplements containing antioxidants, vitamins and minerals have been shown to reduce progression in a subset of patients with age-related macular degeneration in the AREDS studies. In an open label, randomized controlled trials of 117 eyes of 117 patients with mild or moderate POAG, Garcia-Medina et al. explored whether similar preparations could influence structural and functional measures of glaucoma progression over two years of follow-up.

Patients were randomised to receive either daily oral supplementation with ICAPS R (n = 26), OFTAN MACULA (n = 28), or no treatment (n = 63). Humphrey 24-2 perimetry and FD-OCT scans were performed every six months for two years. No statistically significant differences were found on any structural or functional measure between treated and control groups, nor was there any difference in IOP control.

The study is of interest, not least because of a number of contradictory studies in the literature concerning the effects of antioxidants in glaucoma. Although the groups were quite small, the authors estimated they had 80% power to detect a difference in perimetric mean deviation of 0.6dB over two years between treated and control groups. Another limitation was that patients were not masked to their treatment which could potentially affect their attitude to, and thus performance of, automated visual field tests.

Nevertheless, the study suggests that there is unlikely to be a large effect of oral antioxidant supplementation with or without omega-3 fatty acids in the population studied. Given the bias in published literature towards clinical studies with positive finding, and the consequent risk that the literature is skewed as a result, it is good to see carefully performed studies with negative findings being published prominently. Strong negative findings are arguably at least as important as positive results in aiding future clinical treatment decisions.

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