A number of studies are finding that low vitamin D levels are correlated with dry eye. It seems hard to imagine that anyone could have low levels of Vitamin D in Perth given all the sun that we get. However, those with sun damaged skin are very keen to avoid any further sun exposure and this may lead to low levels of vitamin D.
If we look at a recent study Yildirim P., et al. Dry eye in vitamin D deficiency: more than an incidental association. International Journal of Rheumatic Diseases, 2015.
This looked at 2 groups of women who were premenopausal. One group had low vitamin D averaging 33 nm/L and another normal group who averaged 120nm/L of vitamin D.
They looked at 3 measures that might be used to assess dry eye: Schirmer test, tear break up time and the symptoms questionnaire the ocular surface diseases index (OSDI). On all 3 of those measures, the low vitamin D group performed badly from the perspective of dry eye.
On Schirmer’s test, 52% of the low vitamin D group were classified as dry eye vs 4% of the control group.
On the tear break up test, 74% of the low vitamin D group were classified as dry eye vs 12% of controls.
On OSDI 70% had dry eye compared to 20% of controls.
Overall, compelling results.
The authors suggest that that the effect may be due Vitamin D’s role in reducing inflammation. As we all know, inflammation plays a big role in dry eye.
This was a fairly small study with around 50 women in each group and it only shows there was a correlation rather than causation. A search on PUBMED shows more of these studies appearing adding to the strength of evidence.
So the take home message is that there is some evidence low vitamin D is implicated in dry eye. It is fairly easy to have a blood test for vitamin D and if you keep your vitamin D levels at around 125nm/L (50g/ml) you are less likely to be troubled with dry eye.