You’re at the free throw line, ready to make the final shot in a basketball game with seconds on the clock. The stress you’re likely feeling is also affecting the pressure in your eyes, a study in Optometry and Vision Science reports.

Since athletes can experience high levels of anxiety during sports competitions— and intraocular pressure (IOP) often mirrors nervous system changes during mentally demanding situations—Spanish researchers tested whether different levels of induced anxiety during basketball free throw shooting altered IOP.

In this study, 18 amateur basketball players performed three experimental sessions consisting of 100 free throws each. Investigators gave three different instructions to participants regarding the score assigned to each free throw, allowing the researchers to manipulate the level of induced anxiety to low, medium or high.

Basketball players reported more perceived anxiety with higher levels of induced anxiety, and in turn, higher levels of induced anxiety provoked an acute rise in IOP. Of note, the study reported low, medium and high anxiety-induced conditions promoted an average IOP rise of 0.21%, 1.63% and 18.46%, respectively. Additionally, a trend of linear IOP rise over time was seen in the high anxiety-induced condition.

The investigators found no effect of anxiety-induced manipulation on basketball free throw performance.

“Based on these findings, IOP may be considered a promising tool for the assessment of the level of anxiety in certain sport situations. Future studies are required to explore the generalizability of these results in other scenarios with different physical and mental demands,” researchers said.

Vera J, Jiménez R, Redondo B, et al. Intraocular pressure as an indicator of the level of induced anxiety in basketball. Optom Vis Sci. 2019;96(3):64-171.