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

Abstract

Purpose: 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). Methods: 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. Results: 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). Conclusions: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.

Water-drinking Test in Normal Tension Glaucoma Patients with and without High Myopia

“…Ren et al suggest that myopic severity affects NTG as a result of mechanical stretching of the optic nerve and lamina cribosa in relation to axial length 24 . The stretched sclera in myopic eyes may have subsequently causes thinning of the choroid, mechanical stretching of the optic neurons, and damaging of the lamina cribosa 25,26 . Riva et al also suggested that axial length elongation in myopic NTG causes narrowing of the posterior ciliary arteries, whereby reduces the choroidal circulation and blood ow to the lamina cribosa, resulting in choroidal thinning 26 .…”

“…Mansouri et al demonstrated that in healthy subjects following WDT, macular choroidal thickness and choroidal volume increased by 5.7% and 6.4%, respectively 22 , but no positive correlation was observed between IOP and choroidal thickness. Germano et al further studied healthy subjects with and without high myopia and was unable to identify the association between choroidal thickness and IOP elevation 25 . Regarding myopic severity, Sohn et al showed that myopia does not correlate with the progression rate in NTG patients 7 .…”

IMI—The Dynamic Choroid: New Insights, Challenges, and Potential Significance for Human Myopia

“… 156 Another more recent study evaluated the choroidal responses of highly myopic and emmetropic eyes to the water drinking test and found no statistically significant changes related to the water drinking test in either group, although as expected, the choroids of highly myopic eyes were significantly thinner than those of emmetropic eyes. 172 …”

The Effect of Glycemia on Choroidal Thickness in Different Stages of Diabetic Retinopathy

“…However, evaluating the choroid is challenging because there are several ocular and systemic factors that influence the choroid, and thus choroidal thickness (CT), such as choroidal diurnal variation [3], age [4], refractive error, axial length [5], intraocular pressure, ocular perfusion pressure [6], ingestions of water after the water drinking test [7], intraocular anti-vascular endothelial growth factor (anti-VEGF) injection [8], intraocular steroid injection [9], retinal photocoagulation [10], and presence of other retinal or choroidal diseases. Other factors less known to affect the choroid are nicotine use [11], caffeine use [12], presence of autoimmune disease such as Cushing syndrome [13, 14], conditions that affect hemodynamics (e.g., arrhythmia), blood pressure, heart rate [15], and hypercholesterolemia [16].…”