Regional macular and peripapillary vessel density changes associated with the water drinking test

Abstract

Purpose : The water drinking test (WDT) serves as a stress test for the eye and a useful tool to assess circadian peaks and instability of intraocular pressure (IOP). While it has been shown that IOP peaks during WDT may predict future visual field progression in glaucoma patients, the relationship between IOP elevations and retinal microvascular changes remains equivocal. This preliminary study examines changes in macular and peripapillary vessel densities (VD) after WDT in healthy eyes.

Methods : Seven eyes from 7 healthy subjects were included in the study (age 43 ± 5.9 years; baseline axial length 24.35 ± 1.64 mm). All subjects underwent the WDT, which involved drinking 1 liter of water in 5 minutes after 4 hours of fasting. Axial length was measured before the WDT. Intraocular pressure, 6 x 6 mm macular optical coherence tomography angiography (OCTA), and 4.5 x 4.5 mm disc OCTA were obtained at baseline before the WDT and at 15-minute intervals after water ingestion using the Triton (Topcon Healthcare, Tokyo, Japan). IOP changes and regional VD changes in the superficial macula and radial peripapillary capillary were calculated over time.

Results : A moderate positive association was observed between baseline axial length and IOP (R² = 0.40). Significant increases in IOP were detected across all eyes in the first 30 minutes of the WDT (2.7 ± 0.7 mmHg at 15-min and 1.7 ± 1.9 mmHg at 30-min; all P<0.05). In the macula, VDs decreased in the central, inferior, and temporal ETDRS subfields but were not statistically significant (all P>0.05; Figure 1). In contrast, superior VD at 15 minutes was significantly reduced compared to baseline (-1.10 ± 1.23 %; P=0.03). At the optic disc, superior, inferior, and nasal peripapillary VD trended downward while a slight increase was observed in the temporal sector at 15 minutes after water drinking (all P>0.05).

Conclusions : In healthy eyes, the WDT revealed peaks in IOP, accompanied by some observed changes in sectoral VD on both macular and peripapillary OCTA. Future studies with larger and diseased populations are warranted to further investigate IOP spikes and their impact on regional retinal and peripapillary microvascular regulation.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1. Change in regional macular VD vs. time. Significant decrease in superior VD during WDT. Trends of reduction were observed in central, inferior, and temporal macula though not statistically significant.