In the news: Vitamin D May Benefit Dry Eye; Omega-3s Linked to Lower AMD Risk

Vitamin D May Improve Dry Eye Signs, Symptoms

Fat-soluble vitamin D, which is involved in several processes that regulate immune and inflammatory responses, may influence the development of Dry Eye Disease (DED).

Serum vitamin D deficiency, for example, may contribute to conjunctival squamous metaplasia and ocular surface goblet cell loss, which decreases tear film quality and ocular surface wettability.

Deficiency of the vitamin also worsens the ocular inflammatory response in patients with DED, resulting in changes such as damage to Bowman’s layer and recruitment of dendritic cells – antigen-presenting cells that boost immune response.

The increase in corneal dendritic cell density may be related to the severity of DED symptoms likely due to potential effects on the eye’s network of nerves (the sub-basal nerve plexus).

Many studies have explored the relationship between serum and/or tear vitamin D levels and DED. Most, though not all, have reported that decreased vitamin D levels are associated with increased DED risk and/or increased symptoms.

To better clarify whether vitamin D supplementation improves DED, Nanjing University, Dept. of Ophthalmology researchers conducted a meta-analysis(1) of 8 published intervention studies including 439 participants with DED.

Two reviewers independently assessed the quality of the literature and extracted data to calculate standard mean differences for the Schirmer’s test (SH test), tear film break-up time (TBUT), corneal fluorescein staining scores (CFSS, Oxford Scale, 0–5), lid hyperemia, ocular surface disease index (OSDI), and visual analogue pain scale (VAS).

The duration of the intervention ranged from two weeks to six months. Vitamin D was administered orally (commonly 1000-2000 IU daily) in most of the studies, though two studies used intramuscular injections. The analysis showed a statically significant improvement in tear production and tear film stability, and reduced lid hyperemia and OSDI scores.

The authors conclude that vitamin D supplementation could be an adjuvant treatment to alleviate the signs and symptoms of dry eye but point to the need for further, high quality studies to determine the most appropriate administration and dosage.

Inadequate levels of vitamin D have also been tied to other ocular condition such as AMD, diabetic retinopathy and uveitis. It may be prudent to take a daily vitamin D-containing multivitamin, since obtaining sufficient levels from foods alone is difficult.

Omega-3s Again Linked to Lower AMD Risk

A new meta-analysis(2) from the Dept. of Ophthalmology, Jinan University, Guangzhou, China, found that a higher intake of omega-3 fatty acids was associated with a lower risk of AMD, while intake of trans fatty acids was linked to higher AMD risk.

The meta-analysis included 26 observational studies with 241,151 participants. In all but one study, dietary fat intake was assessed using food frequency questionnaires.

Compared to the lowest intakes, the highest intakes of DHA, EPA, and DHA + EPA combined were associated with 20%, 9%, and 21% lower odds of AMD respectively. Additionally, the highest total omega-3 consumption was tied to an 18% lower risk of late-stage AMD. In sub-group analyses, higher trans fatty acid intake was linked with increased risk of late-stage disease.

All studies included in the meta-analysis were of high Methodological quality.

References

1. Chen Z, et al. The efficacy of vitamin D supplementation in dry eye disease: A systematic review and meta-analysis. Cont Lens Anterior Eye. Epub July 16, 2024.
2. Lee Y, et al. Association between fatty acid intake and age-related macular degeneration: a meta-analysis. Front Nutr. 11:1403987, 2024.