Vitamin D and intraocular pressure--results from a case-control and an intervention study.

Purpose:   To study the associations between serum 25-hydroxy-vitamin D (25(OH)D) levels, vitamin D administration and intraocular pressure (IOP).

Methods:   The design of the study included a nested case-control study and a randomized controlled intervention trial. In the first part, healthy Caucasians with high or low serum 25(OH)D levels were recruited from a population-based study. IOP of the right eye was measured by the use of a rebound tonometer. In the second part, those with low serum 25(OH)D levels were randomized to receive either capsules of vitamin D3 20,000 IU twice per week or placebo for 6 months before IOP was measured again.

Results:   Intraocular pressure in the 87 participants with low serum 25(OH)D levels (mean 40.1±12.9 nm) did not differ from IOP in the 42 participants with high serum 25(OH)D levels (mean 85.1±14.0 nm) (15.9±3.3 mmHg versus 15.6±3.1 mmHg, p= 0.56, independent t-test). After intervention, IOP decreased by -0.8± 2.1 mmHg (p = 0.017, paired t-test) in the vitamin D group (n= 39) and -0.8±2.5 mmHg (p= 0.059) in the placebo group (n= 39), but the change was not significantly different between the groups (p= 0.92, independent t-test).

Conclusion:   This study in healthy participants revealed no associations between serum 25(OH)D levels and IOP, and administration of vitamin D3 to participants with low levels of 25(OH)D did not affect IOP. These results do not support a role of vitamin D in the regulation of IOP.