Effect of repeated endurance exercise on intraocular pressure in healthy subjects: a prospective pilot study based on a 500-km swim relay

Aim of the study
To investigate exercise-related changes in the intraocular pressure (IOP) in healthy participants of a 500-km swim relay.

Material and methods
A group of 12 well-trained amateur swimmers aged 13-67 years participated in a 500-km swim relay in the Warta River, Poland. Each participant underwent detailed clinical examinations, including IOP and central corneal thickness measurements, 2-3 weeks before the relay (baseline) and at peak effort (10 min after the last shift). A baseline maximal treadmill exercise test was also conducted for measurement of the maximal oxygen consumption (VO₂) and metabolic equivalent of task (MET) values.

Results
None of the athletes (12 eyes) exhibited significant changes in IOP at peak effort (mean change from 14.3 to 15.4 mmHg, p > 0.05). Six male subjects exhibited an exercise-induced mean increase in IOP at peak effort, from 15.6 to 18.5 mmHg (6 eyes, p < 0.05). In six female subjects, the peak effort was not associated with significant IOP changes; IOP mean declined slightly from 13.0 to 12.3 mmHg (6 eyes, p > 0.05). IOP parameters, including the pressure at rest, pressure at peak effort, and pressure change, showed no significant correlations with cardiorespiratory aerobic fitness determined by VO₂ and MET.

Conclusions
This pilot study did not reveal changes in IOP among well-trained amateur athletes in response to prolonged vigorous swimming. These results, as well as sex-specific differences, in IOP changes at peak effort due to the small sample size must be confirmed by examinations in a larger group.