Changes of choroidal structure and circulation after water drinking test in normal eyes

Purpose To determine whether water drinking test (WDT) alters choroidal structure using binarization of enhanced depth imaging optical coherence tomographic (EDI-OCT) images. Methods We performed a prospective study of 57 eyes of 57 normal subjects. The intraocular pressure (IOP), EDI-OCT images, and laser speckle flowgraphic images were recorded at baseline, and at 15, 30, 45, and 120 min after the WDT. The EDI-OCT images were converted to binary images using ImageJ software, and we examined luminal area, interstitial area, whole choroidal area, the ratio of luminal area to whole choroidal area (L/W ratio), subfoveal choroidal thickness (SCT), and central retinal thickness (CRT). Results The luminal area, L/W ratio, whole choroidal area, and IOP were significantly increased 30 min after water drinking; levels returned to the baseline at 120 min. No significant changes were found in the CRT and interstitial area. The fluctuations in the SCT after water intake were significantly correlated with those in the L/W ratio and luminal area but not with those of the interstitial area. The choroidal blood flow velocity was significantly decreased at 30 min. Fluctuations in the luminal area, L/W ratio, and whole choroidal area were significantly correlated with IOP fluctuations. Conclusions The changes in the SCT after water drinking were mainly due to the changes in the choroidal vascular space. Dilatations of the choroidal vessels after water drinking may lead to choroidal thickening and subsequent IOP elevation. These findings should be considered in the evaluation of choroidal structure in patients with retinal disease.