The Effect of Dynamic and Isometric Exercise on Refractive State, Accommodation and Intra-Ocular Pressure

Abstract

Introduction: Several studies have demonstrated that an increase in the number of hours children spend outdoors is associated with reduced myopia progression One suggestion is that physical exercise could affect refractive development, either through a change in the accommodative response or IOP. This study evaluated the effect of both isotonic and isometric exercise on these ocular parameters. Methods: 20 young, healthy subjects participated in 3 trials. In the first trial, subjects spent 10 minutes exercising on a stair climbing machine while in the second session, they were required to maintain an unsupported squat position for a continuous 2 minute period. In a control condition, subjects watched television in a seated position for 10 minutes. Before and immediately after each trial, the following parameters were measured: (i) systolic and diastolic BP, (ii) heart rate, (iii) distance refractive state, (iv) accommodative response to 3, 4 and 5D stimuli and (v) IOP. In a second study, IOP was assessed both before and during (while the subject was still in the squatting position) 1 minute of isotonic exercise in 14 young, healthy subjects. Results: A significant increase of 32 mmHg in systolic BP was observed following the stair climbing exercise while significant increases in heart rate were recorded following both the stair climbing and squatting trials. However, no significant changes in IOP, distance refractive state or accommodative response were noted following any of the 3 conditions. In the second study, mean IOP before and during the squatting exercise was 14.6 and 19.1 mm Hg, respectively (p < 0.0001). Conclusions: Brief periods of exercise do not produce significant changes in refractive state, accommodation or IOP. Although a significant change in IOP was observed during the course of isometric exercise, this effect dissipated rapidly. While a cumulative effect may exist following longer or multiple exercise sessions, there is no support for the proposal that physical exercise will alter refractive development or progression.