Illustration of eye with choroid layer and water droplets

Water Drinking Test: New Insights into Myopia and Eye Pressure

Rhea Morgan in Health & Wellness December 2025 • 4 min read.

"Uncover how the water drinking test reveals the choroid's role in intraocular pressure in myopic eyes."

Myopia, or nearsightedness, affects millions worldwide and is classified into low-to-moderate and high or pathological types. High myopia can lead to serious complications like macular atrophy and retinal detachment. These issues are often linked to the excessive elongation of the eyeball, causing a decrease in the thickness of the choroid, a vascular layer beneath the retina.

Recent advances in imaging technology, specifically spectral-domain optical coherence tomography (SD-OCT), have allowed for better visualization and measurement of the choroid. This improved imaging has opened new avenues for understanding how the choroid behaves under different conditions. One such condition is the water drinking test (WDT), typically used in glaucoma diagnostics, where patients consume a large amount of water in a short period.

While the WDT has been used to assess the eye's outflow facility reserve, its impact on choroidal thickness in myopic eyes remains less understood. A new study aims to evaluate how choroidal thickness changes during the WDT in individuals with high myopia compared to those with normal vision, shedding light on potential mechanisms affecting intraocular pressure (IOP).

How Does Choroidal Thickness Vary in Myopic Eyes During the Water Drinking Test?

Illustration of eye with choroid layer and water droplets

The study involved 30 participants, divided into two groups: those with high myopia (ME) and those with normal vision (EE). Participants underwent the WDT, and their choroidal thickness was measured using SD-OCT at baseline, 10 minutes, and 45 minutes after water ingestion. Researchers analyzed the average macular choroidal thickness and IOP changes during the test.

The findings revealed that individuals with normal vision had greater choroidal thickness compared to those with high myopia, specifically at the fovea and at points both nasal and temporal to the fovea. While choroidal thickness varied significantly in both groups 10 minutes after water ingestion, no significant differences were observed between the groups. Additionally, a moderate correlation was found between the peak IOP during the WDT and choroidal thickness in myopic eyes.

Choroidal Thickness: Emmetropic eyes (EE) exhibited greater choroidal thickness compared to myopic eyes (ME) at baseline measurements.
Water Drinking Test Response: Both EE and ME groups experienced significant changes in choroidal thickness, particularly at the fovea 10 minutes post-water ingestion.
Intraocular Pressure Correlation: A moderate correlation was observed between IOP peaks during the WDT and choroidal thickness in ME.

These results suggest that the choroidal bed behaves similarly in both myopic and non-myopic eyes during the WDT. However, the study confirms that individuals with high myopia have thinner choroids, and choroidal thickness variation may not fully explain the IOP elevations observed during the WDT. This indicates that other factors, such as aqueous humor dynamics and outflow facility, may play a more significant role in IOP regulation during the WDT.

Implications and Future Directions

The study's findings contribute to a better understanding of the relationship between myopia, choroidal thickness, and intraocular pressure. While choroidal thickness variations do not fully explain IOP elevations during the WDT, the study underscores the importance of considering choroidal characteristics in myopic eyes.

Future research should explore other factors influencing IOP during the WDT, such as aqueous humor dynamics and outflow facility, to provide a more comprehensive understanding of IOP regulation in myopic eyes. Additionally, longitudinal studies could investigate the long-term effects of choroidal thickness changes on visual outcomes in individuals with high myopia.

By continuing to investigate the complex interplay between myopia, choroidal health, and intraocular pressure, researchers can develop targeted interventions to prevent vision-threatening complications and improve the quality of life for individuals with myopia.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.5935/0004-2749.20160062, Alternate LINK

Title: Choroidal Thickness Variation In Highly Myopic Eyes During The Water Drinking Test

Subject: Ophthalmology

Journal: Arquivos Brasileiros de Oftalmologia

Publisher: GN1 Genesis Network

Authors: Renato Antunes Schiave Germano, Marcelo Hatanaka, Remo Susanna Junior

Published: 2016-01-01

Everything You Need To Know

What does the water drinking test involve, and what is it primarily used to assess?

The water drinking test (WDT) involves consuming a large amount of water in a short time, typically used in glaucoma diagnostics. While the study focuses on choroidal thickness, the WDT is more broadly used to assess the eye's outflow facility reserve. The intraocular pressure (IOP) is measured before and after water consumption to observe how the eye regulates pressure, helping to identify potential issues with aqueous humor drainage.

How does spectral-domain optical coherence tomography contribute to understanding the choroid's role in eye conditions?

Spectral-domain optical coherence tomography (SD-OCT) is an advanced imaging technology that allows for detailed visualization and measurement of the choroid. SD-OCT enables researchers to observe the choroid's structure and thickness under different conditions, such as during the water drinking test (WDT). This technology has significantly enhanced our understanding of the choroid's role in various eye conditions, including myopia.

How does choroidal thickness change in myopic versus normal eyes during the water drinking test?

During the water drinking test (WDT), choroidal thickness changes significantly in both myopic eyes (ME) and emmetropic eyes (EE) 10 minutes after water ingestion, particularly at the fovea. While individuals with normal vision had greater choroidal thickness compared to those with high myopia at baseline, the variation in choroidal thickness does not fully explain the intraocular pressure (IOP) elevations observed during the WDT. This suggests other factors, such as aqueous humor dynamics, are involved in IOP regulation.

Is there any relationship between intraocular pressure and choroidal thickness during the water drinking test in myopic eyes?

The study revealed a moderate correlation between peak intraocular pressure (IOP) during the water drinking test (WDT) and choroidal thickness in myopic eyes (ME). This suggests a relationship between choroidal characteristics and IOP in myopic individuals. However, the choroidal thickness variation does not fully explain the IOP elevations, indicating that other factors like aqueous humor dynamics and outflow facility are also at play.

What are the broader implications of these findings on choroidal thickness and intraocular pressure, and what further research could be conducted?

This research suggests that the characteristics of the choroid are important in myopic eyes, even though changes in the choroid's thickness don't fully explain the pressure changes in the eye during the water drinking test. Further research could explore how the choroid interacts with other eye structures and fluids, like the aqueous humor, to influence intraocular pressure and overall eye health in people with myopia. Further insights may come from longitudinal studies, which would track choroidal changes over time.