Choroidal thickness variation in highly myopic eyes during the water drinking test

To evaluate variations in choroidal thickness (CT) during the water drinking test (WDT) in emmetropic eyes (EE) and highly myopic eyes (ME) using spectral-domain optical coherence tomography (SD-OCT).

Clinical trial performed at a tertiary care hospital comprising 30 randomly selected eyes. The WDT and SD-OCT macular scans were performed 10 and 45 min after water ingestion in 15 myopic and 15 EE of 15 healthy patients in each group. Primary study outcomes were average macular CT measured by SD-OCT and intraocular pressure (IOP) during the WDT.

The mean spherical equivalent refraction was 0.15 ± 0.24 D in emmetropic and -7.1 ± 1.75 D in ME (p<0.001). No statistical differences between EE and ME were observed during the WDT response. EE had higher CT compared with ME at the fovea (361.4 ± 55.4 vs 257.9 ± 95.3; p<0.001), 3 mm nasal to the fovea (158.0 ± 71.8 vs 122.5 ± 54.5; p =0.047), and 3 mm temporally to the fovea (310.6 ± 52.4 vs 247.6 ± 90.1; p=0.05). Regarding CT variation, significant differences in foveal CT at 10 min after water ingestion were observed in both EE and ME, with no statistically significant difference observed between groups. A moderate correlation between IOP peak during the WDT and CT was demonstrated in ME (r=0.52; p=0.04).

No statistically significant differences in CT variation during the WDT were observed between EE and ME, indicating similar behavior of the choroidal bed during the WDT in both groups. Further, CT was thinner in highly ME, with CT variation unable to explain elevations in IOP observed during the WDT.