A recent study found that older patients with vitamin D insufficiency have a reduced macular thickness compared to those without vitamin D insufficiency.
The macula is the highly-pigmented yellowish area in the center of the retina in the eye and is the region of the greatest visual perception. Vitamin D receptors have been found on the macula, suggesting that vitamin D plays a role in macular and overall vision health.
Epidemiological studies have found associations between vitamin D levels and impaired visual acuity, as well as an association between vitamin D levels and age-related macular degeneration (AMD). AMD is a medical condition that usually results in a loss of vision in the center of the visual field due to damage of the retina and is characterized by the thinning of the macula.
There have been no randomized controlled trials that have examined the role of vitamin D supplementation in treating or preventing visual loss and/or AMD.
Recently, researchers conducted a study to determine whether vitamin D insufficiency is associated with reduced macular thickness among participants without macular pathology. This allows them to examine a more general relationship of vitamin D on macular health without the clinical impact of AMD, as AMD patients are often instructed to avoid sunlight, which worsens the condition. A collaboration of researchers from four different countries studied 62 older individuals (mean age 70.9 years) recruited for the Gait and Alzheimer Interactions Tracking (GAIT) study. The GAIT study is an observational, cross-sectional study designed to examine gait in older community-dwellers reporting subjective memory complaints.
Measurements of macular thickness and vitamin D levels were taken. Vitamin D insufficiency was defined as levels below 20 ng/ml.
Statistical analyses of the two variables revealed the following:
- The average vitamin D level was 24.4 ng/ml.
- Seventeen participants (27.4%) had vitamin D insufficiency.
- There was a significant association between vitamin D insufficiency and macular thickness.
- This association remained significant even after adjustment for all potential confounders.
- Participants with vitamin D insufficiency had 3.7 times the risk of abnormally low macular thickness compared to those with sufficient levels.
Researchers summarized the results by stating,
“The main finding of this [optical coherence tomography] study is that, irrespective of all measured potential confounders, vitamin D insufficiency was associated with a thinner central macular thickness among older adults with no patent macular dysfunction. To the best of our knowledge, this study is the first to assess and report such an association. This novel finding is consistent with the result of a recent study highlighting an association between vitamin D insufficiency and impaired visual acuity in older adults.”
This study does not establish causation but lends more evidence to the hypothesis that vitamin D plays a causative role in the progression of AMD.
There are some limitations to note in this study. The study cohort was relatively healthy older participants who might not represent the population of all seniors. The cohort was also relatively small. Lastly, a small proportion of participants had other ocular conditions, such as a history of severe myopia.
Further longitudinal, observational cohort studies are needed to validate these results in large populations before intervention trials are warranted.