Correlation between tear fluid and serum vitamin D levels

Abstract

Background: Vitamin D deficiency is associated with a range of systemic diseases including ocular disorders. The objective of this study is to measure tear vitamin D levels and investigate the correlation between serum and tear vitamin D levels. Methods: A total of 48 healthy volunteers without any systemic and ocular disease were recruited for this observational cohort study. Serum was collected using clot activator coated Vacutainer® Plus tubes. Tear fluid was collected using Schirmer's strips. Serum and tear total 25-hydroxyvitamin D levels were measured by competitive chemiluminescent ELISA and the correlation between the levels were studied. Results: The measured serum 25-hydroxyvitamin D level ranged between 3.3 and 27.5 ng/ml (Mean ± SEM, 9.4 ± 0. 7 ng/ml; Median 8.4 ng/ml). Significantly (p < 0.0001) higher level of 25-hydroxyvitamin D was detected in the tears (Mean ± SEM, 17.0 ± 1.6 ng/ml; Range 3.2-45.8 ng/ml; Median, 16.3 ng/ml) compared to serum. An average of~2 fold (Mean ± SEM, 1.9 ± 0.2; Range 0.4-5.8; Median, 1.7) higher 25-hydroxyvitamin D was observed in tears compared to serum in the subjects. In addition, a positive correlation was observed between serum and tear 25-hydroxyvitamin D levels (r = 0.5595; p < 0.0001). Conclusions: A higher level of 25-hydroxyvitamin D was observed in the tear fluid compared to that of the serum. It would be beneficial to consider tear vitamin D levels to study its role with reference to ocular surface diseases.

Determination of vitamin D in tears of healthy individuals by the electrochemiluminescence method

“…Results here described contribute to the observation of the possibility of using the electrochemiluminescence method for the detection of vitamin D levels in both blood and tear fluid. It was observed that the mean level of vitamin D is higher in tear fluid than in the blood in this study, which was also verified in the experiment performed by Sethu et al To our knowledge, the cause of this fact and the discrepancy between vitamin D levels of the two biological materials remain unclear.…”

“…Research on vitamin D testing can be performed by various types of laboratory methods, such as chemiluminescent microparticle immunoassay (CMIA) and ELISA . Results here described contribute to the observation of the possibility of using the electrochemiluminescence method for the detection of vitamin D levels in both blood and tear fluid.…”

“…It has been found that the amount of this vitamin is higher in tear fluid than in blood in patients with eye diseases. In addition, some studies show that there are contradictions between the serum value of 25‐hydroxyvitamin D with dry eye disorder; therefore the measurement of 25‐hydroxyvitamin D in tears may be more relevant for ocular diseases, especially for ocular surface diseases …”

Dry eye disease and oxidative stress

“…Serum vitamin D levels are positively correlated to tear vitamin D levels, with tear vitamin D levels being higher than that of serum levels (Sethu et al. ). This suggests that orally supplementing the levels of systemic vitamin D may increase tear levels.…”

“…Vitamin D is a potent antioxidant, and patients with increased levels of serum vitamin D levels were found to have increased BUT and tear secretion (Jin et al 2017). Serum vitamin D levels are positively correlated to tear vitamin D levels, with tear vitamin D levels being higher than that of serum levels (Sethu et al 2016). This suggests that orally supplementing the levels of systemic vitamin D may increase tear levels.…”