Researchers show hypercapnia reduces IOP

SEATTLE – Hypercapnia, or increasing the blood concentration of carbon dioxide by rebreathing into a paper bag, causes a significant reduction in IOP, according to a poster presentation here at Optometry’s Meeting.

“This is a way to look at a possible mechanism for the reduction of IOP that results after exercise,” James LaMotte, OD, PhD, told PRIMARY CARE OPTOMETRY NEWS in an interview.

Researchers took the baseline IOP measurements of 14 young, normal patients with Goldmann tonometry and a second measurement after those same patients rebreathed into a paper bag for 10 minutes. Measurements were taken again 7 minutes later. The change of IOP from baseline after 10 minutes was not statistically significant in either the right eye (p=0.089) or the left eye (p=0.055), but the change from baseline to the final measurement was significant. The right eyes went from 14.1 mm Hg average at baseline to 13.1 mm Hg after 7 minutes of normal breathing, and the left eye dropped from a 14.2 mm Hg average to 12.9 mm Hg.

Dr. LaMotte said it is well known that moderate aerobic exercise results in a significant reduction of IOP, but the mechanisms of how that works are still not understood. It can be surmised from this research that exercise-induced hypercapnia may be involved, but “the next step would be to see how long the IOP-lowering effects would last,” he said.