Effect of transient increase in intraocular pressure on anterior eye parameters

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Abstract
Transient changes in intraocular pressure (IOP) cause axial elongation and choroidal thinning; however, associated effects on anterior eye components which could be relevant to myopia remain unclear. This study aimed to investigate the impact of transient IOP changes on anterior eye and to assess the repeatability of anterior chamber measurement and segmentation. The right eye of 21 healthy adults (40 ± 16 years) was included. Baseline axial length and anterior chamber parameters including anterior chamber angle, anterior chamber depth, angle opening distance (AOD), and trabecular iris space area (TISA) were measured three times using optical coherence tomography. Participants wore modified swimming goggles to induce a transient change in IOP. The same parameters were measured 5 minutes after wearing and immediately upon removal of the swimming goggles. ANOVA was used to assess the effects of IOP change on the anterior eye. Intrasession repeatability of semi-automated segmentations was calculated using within-subject standard deviation. Swimming goggles increased IOP (2.4 ± 2.7 mmHg, p < 0.05) and axial length (16 ± 25 µm, p < 0.05). Transient increase in IOP had no effects on anterior chamber parameters (all p > 0.05); however, negative correlation was found between change in IOP and change in nasal anterior chamber angle (r = -0.47) and between age and change in anterior chamber depth (r = -0.44). Within-subject SD of three repeated scans of AOD500, AOD750, TISA500, TISA750 for nasal angle were 36μm, 63μm, 11μm2, and 21μm2 and for temporal angle were 79μm, 98μm, 27μm2, and 46µm2, respectively. Transient increase in IOP led to axial elongation but had no significant effect on anterior eye parameters. A greater increase in IOP correlated with greater narrowing of nasal anterior chamber angle. Semi-automated segmentation of the angle parameters provided repeatable measurements; however, the repeatability was worse in the temporal compared to the nasal quadrant.

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