In the news: Omega-3 as Adjunct in Diabetic Macular Edema Treatment; Vitamin A & Retinitis Pigmentosa in Children

Omega-3 Fatty Acids & Diabetic Eye Disease

Previously, an analysis of the PREDIMED trial found that participants with type 2 diabetes consuming at least 500 mg daily of EPA and DHA and followed for 6 years, had a 48% decreased risk of sight-threatening diabetic retinopathy (1). That study, published in JAMA Ophthalmology in 2016, increased awareness of the potential role of these long-chain omega-3 fatty acids in diabetic eye disease.

Long chain omega-3s may also favorably impact the treatment of diabetic macular edema, according to the 3-year results of a single blind, randomized controlled trial published last month in the journal Retina (2).

In this study, the effects of the anti-VEGF drug ranibizumab alone, or combined with a daily dose of DHA (1,050 mg), EPA (147 mg) and antioxidants were evaluated in patients with diabetic macular edema. Twenty-six patients (31 eyes) received the drug plus the nutritional supplement, while the drug alone was administered to 29 patients (38 eyes). In both groups, intravitreal ranibizumab (0.5 mg) was given monthly for the first 4 months, followed by a pro re nata (as needed) regimen throughout the trial. The treatment evaluator was masked to the patients’ assigned treatment.

At 36 months, there was a greater mean decrease of central subfield macular thickness (CSMT) in the supplemented group than in controls (275 vs. 310 micrometer). Between group differences in CSMT measures were significant at 25 months (p = 0.024), months 30 (p = 0.05), 33 months (p = 0.011), and 34 months (p = 0.039).

Between group differences in serum HbA1c, plasma total antioxidant capacity values, erythrocyte DHA content, and serum IL-6 levels were all significant in favor of the supplemented group at 36 months.

In short, patients receiving omega-3s and antioxidants achieved better-sustained improvement in CSMT outcome than ranibizumab alone. These results are promising, and augmenting anti-VEGF treatment with omega-3 and antioxidants deserves further study using a larger sample size and a double-blind design.

Vitamin A Associated with Slower Progression of Retinitis Pigmentosa in Children

In 1993, the results of a randomized clinical trial of 601 adults (18-46 years) with the common forms of retinitis pigmentosa treated with vitamin A and/or vitamin E for 4 to 6 years were reported (3). Vitamin A palmitate, 15,000 IU/d, on average, slowed the course of retinal degeneration, while oral vitamin E (400 IU/day, on average), appeared to hasten the course of retinal degeneration as monitored by full-field cone ERG to 30-Hz flashes.

The authors of that earlier investigation conducted a case-control study of children with common forms of retinitis pigmentosa to assess whether the mean course of the disease monitored by ERG in 55 children receiving vitamin A differed from a control cohort of 25 unsupplemented children.

The age-adjusted doses were 5,000 IU/day for ages 6 up to10 years, 10,000 IU/day for ages 10 to 15 years, and 15,000 IU/day for those 15 and older. All children taking vitamin A had normal serum liver function test results prior to supplementation.

Vitamin A supplementation was associated with a nearly 50% slower loss of cone ERG amplitude. The mean rates of decline were estimated to be 13.2% per year in the unsupplemented control cohort and 6.9% per year in the cohort taking vitamin A. The authors report finding no safety concerns linked to supplemental vitamin A.

While the findings are not definitive because of the relatively small sample and retrospective, non-randomized study design, they suggest that vitamin A is beneficial in children with retinitis pigmentosa.  

References

1. Sala-Vila A, et al. Dietary marine ω-3 fatty acids and incident sight-threatening retinopathy in middle-aged and older individuals with type 2 diabetes: prospective investigation From the PREDIMED Trial. JAMA Ophthalmol. 134:1142-49, 2016.
2. LaFuente M, et al. Three-year outcomes in a randomized single-blind controlled trial of intravitreal ranibizumab and oral supplementation with DHA and antioxidants for diabetic macular edema. Retina. 0:1–8, 2018
3. Berson EL, et al. Association of Vitamin A Supplementation with disease course in children with retinitis pigmentosa. JAMA Ophthalmol. EPub March 29, 2018