Water drinking influences eye length and IOP in young healthy subjects

This study aimed to investigate the influence of water loading upon intraocular pressure (IOP), ocular pulse amplitude (OPA) and axial length. Twenty-one young adult subjects who were classified based on their spherical equivalent refraction as either myopes (n = 11), or emmetropes (n = 10) participated. Measures of IOP, OPA and ocular biometrics were collected before, and then 10, 15, 25 and 30 min following the ingestion of 1000 ml of water. Significant increases in both IOP and OPA were found to occur following water loading (p < 0.0001), with peaks in both parameters occurring at 10 min after water loading (mean +/- SEM increase of 2.24 +/- 0.31 mmHg in IOP and 0.46 +/- 0.06 mmHg in OPA). Axial length was found to reduce significantly following water loading (p = 0.0005), with the largest reduction in axial length evident 10 min after water drinking (mean decrease 12 +/- 3 microm). A significant time by refractive error group interaction (p = 0.048) was found in axial length, indicative of a different pattern of change in eye length following water loading between the myopic and emmetropic populations. The largest difference in axial length change was evident at 10 min after water loading with a 17 +/- 5 microm reduction in axial length evident in the myopes and only a 6 +/- 2 microm reduction in the emmetropes. These findings illustrate significant changes in ocular parameters in young adult subjects following water loading.