Effects of laughter exercise on intraocular pressure, Schlemm's canal and chorioretinal parameters in healthy adults

This study investigated the effects of laughter exercise on IOP, anterior and posterior segment parameters in healthy adults.

This study involved 23 healthy adults who underwent baseline and post-intervention measurements of IOP and ocular structures. Using swept-source OCT(SS-OCT), we quantified Schlemm's canal area (SCAR) and trabecular meshwork thickness across four quadrants, and assessed posterior segment parameters with a 24 × 20 mm ultra-widefield protocol. Measurements were repeated at 1, 15, 30, and 60 min after a 5-minute standardized laughter exercise to analyze longitudinal changes and IOP correlations.

IOP significantly decreased at 1, 15, and 30 min after laughter exercise (all p < 0.01), then recovered at 60 min(p = 0.131). The nasal SCAR significantly enlarged at 15 min(p < 0.001) and 30 min post-exercise(p = 0.004). Temporal SCAR only showed significant increase at 1 min post-exercise(p = 0.025). The superior SCAR significantly enlarged at 1 min(p = 0.008) and 30 min(p = 0.041) post-exercise. Inferior SCAR remained stable throughout the study period(p = 0.204). The trabecular meshwork thickness in all 4 quadrants only exhibited significant increase at 1 min post-exercise(all p < 0.01). No significant changes in chorioretinal parameters were noted (all p > 0.05). In the multivariate model, retinal superficial capillary plexus vessel density positively corelated with IOP (β=4.00, p = 0.009), whereas nasal SCAR demonstrated a negative correlation (β=-2.40, p = 0.003).

The anterior and posterior segment demonstrated distinct responses to a standardized laughter exercise. The IOP changes are associated with the expansion of Schlemm's canal. Further research is warranted to determine the efficacy of laughter exercise as a non-pharmacological adjunct for IOP control.