Vitamin D levels and dry eye symptoms may be linked in older adults

Symptoms of dry eye may be associated with vitamin D levels, according to researchers. A recent study revealed that, in older individuals, low vitamin D levels of less than 50 nmol/l were associated with dry eye symptoms, but not in those with diagnosed dry eye. Further, vitamin D supplementation not only increased vitamin D levels, but improved dry eye symptoms, tear quality, and ocular surface conditions. Results are currently in press with Contact Lens & Anterior Eye.

Chih-Huang Yang, PhD student, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Queensland, Australia, and colleagues conducted three linked studies to assess the possible association between serum vitamin D levels and dry eye symptoms, as well as to determine whether oral vitamin D supplementation would have an impact on dry eye. They enrolled 29 older adults in the first study, 29 dry eye subjects in the second, and 32 subjects with dry eye and low serum vitamin D levels in the third.

In all three studies, they assessed all subjects using the Ocular Surface Disease Index (OSD) to measure dry eye symptoms. Additional tests included the phenol red thread test (PRT) and/or Schirmer’s test, tear meniscus height, non-invasive tear break up time (TBUT), grading ocular surface redness, and fluorescein corneal stain. Finally, Yang and colleagues collected blood samples from all patients to analyze serum vitamin D and interleukin-6 (IL-6) levels.

In older subjects, researchers found a negative correlation between vitamin D levels and dry eye symptoms or the severity of dry eye. Vitamin D levels were, however, associated with tired eye symptoms.
In subjects with a diagnosis of dry eye, vitamin D levels were not correlated with OSDI scores or IL-6 levels, but IL-6 levels were correlated with tear production.

In patients in the supplement study, vitamin D levels increased by 29 nmol/l, with significant reductions in both dry eye symptoms and grading of corneal staining. IL-6 levels exhibited no significant changes.

“The decrease in Oxford grading of corneal staining after vitamin D supplement might imply that increased vitamin D levels resulted in an improvement in tear quality and/or health of epithelial cells,” noted Yang and colleagues.

“Our study suggests that monitoring serum vitamin D levels when managing dry eye might be useful; whereby if vitamin D is low, a supplement might be of benefit. A further study with a longer treatment duration and larger participant group would be useful,” they concluded.