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 D 3 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 n m ) did not differ from IOP in the 42 participants with high serum 25(OH)D levels (mean 85.1 ± 14.0 n m ) (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 D 3 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.