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

Comparison of intraocular pressure profiles during the water drinking test and the modified diurnal tension curve

OBJECTIVES

To compare intraocular pressure (IOP) during the water drinking test (WDT) and modified diurnal tension curve (mDTC) in open-angle glaucoma (OAG) patients, using multimodal, observer-masked tonometry.

METHODS

Open-angle glaucoma subjects were prospectively enroled, excluding those who had undergone glaucoma filtration or laser surgery. Two-hourly mDTC Goldmann applanation (GAT) and rebound tonometry (RT) was performed between 8:00 and 16:00, and every 15 min for 45 min after ingestion of 800mls of water. Blood pressure, heart rate, pupillometry measurements, and optical coherence tomography (AS-OCT) were also recorded.

RESULTS

Forty-two subjects' right eyes were included. 48% were using topical glaucoma medication. Mean baseline IOP was 14.9 ± 4.52 mmHg, with mean visual field mean deviation (±SD) -5.05 ± 5.45 dB. Strong association was found between maximum IOP during mDTC and WDT (r = 0.90, 95% CI 0.82-0.95 p < 0.0001) with agreement (mDTC-WDT) bias -0.82 mmHg, 95% LoA -1.46 to -0.18. During the WDT, mean systolic blood pressure (±SD) increased from 140.0 ± 20.0 to 153.3 ± 24.0 mmHg (p < 0.0001), mean heart rate ( ± SD) reduced from 69.5 ± 11.3 bpm to 63.6 ± 10.0 bpm (p < 0.0001), and temporal iridocorneal angle increased from 29.2 ± 6.0° to 29.6 ± 5.2° (p = 0.04).

CONCLUSION

This study presents repeated, observer-masked IOP data showing strong correlation between maximum IOP during mDTC and WDT using multimodal tonometry. This supports WDT as a meaningful alternative to mDTC when investigating diurnal IOP characteristics in clinic, with reduced time requirements and associated costs.

Relationship between vitreous interleukin-6 levels and vitreous particles findings on widefield optical coherence tomography in posterior uveitis

PURPOSE

To investigate relationship between vitreous interleukin-6 levels and vitreous particles findings on widefield optical coherence tomography in posterior uveitis.

METHODS

This retrospective study examined vitreous inflammatory cells (hyperreflective particles) of posterior uveitis on widefield optical coherence tomography (WOCT). We examined the number of hyperreflective particles (possibility of vitreous inflammatory cells) observed on WOCT and the correlations with interleukin-6 (IL-6) levels. The relationship between vitreous IL-6 levels and image findings from WOCT from 37 eyes (34 patients) with posterior uveitis were analyzed. Mean patient age was 63.4±15.7 years. (Mean± standard deviation) IL-6 concentration in vitreous humor was 79.9±7380.9 pg/mL Uveitis was infectious in 9 cases and non-infectious in 28 cases with multiplex polymerase chain reaction system. We measured the number and size of vitreous cells in the posterior vitreous, defined as the space between the upper vitreous and the internal limiting membrane on WOCT at the macular, upper, and lower regions. Image analysis software was also used for cell counting.

RESULTS

A strong correlation was seen between human and software counts. Pearson's correlation coefficient (PCC) was performed to compare categorial variables (on macular +0.866; upper cavity +0.713; lower cavity +0.568; total vitreous cavity +0.834; P<0.001 each). IL-6 levels correlated with both vitreous cell counts and cell counts observed on macular WOCT (human-counted group +0.339, P = 0.04; software-counted group +0.349, P = 0.03). Infectious uveitis showed higher IL-6 levels (P = 0.016) and high cell counts compared with non-infectious uveitis (P = 0.04).

CONCLUSIONS

Vitreous number of hyperreflective particles (cells) findings on WOCTcorrelated well with human and software cell counts. Vitreous cells findings on WOCT also correlated with IL-6 concentrations on macular.

Alterations in choroidal vascular structures due to serum levels of vascular endothelial growth factor in patients with POEMS syndrome

A higher serum vascular endothelial growth factor (VEGF) level can cause choroidal thickening in the choroid of patients with polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes (POEMS) syndrome. We aimed to determine whether fluctuations in serum VEGF levels affect choroidal vascular structures in patients with POEMS syndrome. This retrospective observational case series examined 17 left eyes of 17 patients with POEMS syndrome. Enhanced depth imaging optical coherence tomography (EDI-OCT) images were obtained, and serum VEGF levels were measured at baseline and 6 months after transplantation with dexamethasone (n = 6), thalidomide (n = 8), or lenalidomide (n = 3). EDI-OCT images were binarized using ImageJ software, and we calculated the areas of the whole choroid and the luminal and stromal areas. Subsequently, we determined whether the choroidal vascular structure had changed significantly between baseline and 6 months after treatment. Six months after treatment, serum VEGF levels and the whole choroid, luminal, and stromal areas had decreased significantly compared to the baseline values (all, P < 0.001). The mean luminal area to the whole choroidal area ratio at 6 months after treatment was 0.70 ± 0.03, which was significantly smaller than the ratio at baseline (0.72 ± 0.03; P < 0.001). Whole choroid and luminal area fluctuations were significantly positively correlated with fluctuations in serum VEGF levels (r = 0.626, P = 0.007 and r = 0.585, P = 0.014, respectively). Choroidal thickening induced by VEGF might be caused by increases in the choroidal vessel lumen area. These results may offer insights into the pathogenesis of POEMS syndrome and the role of serum VEGF in choroidal vascular structure, which may apply to other ocular diseases.

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

The choroid is the richly vascular layer of the eye located between the sclera and Bruch's membrane. Early studies in animals, as well as more recent studies in humans, have demonstrated that the choroid is a dynamic, multifunctional structure, with its thickness directly and indirectly subject to modulation by a variety of physiologic and visual stimuli. In this review, the anatomy and function of the choroid are summarized and links between the choroid, eye growth regulation, and myopia, as demonstrated in animal models, discussed. Methods for quantifying choroidal thickness in the human eye and associated challenges are described, the literature examining choroidal changes in response to various visual stimuli and refractive error-related differences are summarized, and the potential implications of the latter for myopia are considered. This review also allowed for the reexamination of the hypothesis that short-term changes in choroidal thickness induced by pharmacologic, optical, or environmental stimuli are predictive of future long-term changes in axial elongation, and the speculation that short-term choroidal thickening can be used as a biomarker of treatment efficacy for myopia control therapies, with the general conclusion that current evidence is not sufficient.

The Effect of the Water Drinking Test on Ocular Parameters and Choroidal Thickness in Glaucoma Suspects

Background and objectives: We aimed to evaluate the effects of the water drinking test (WDT) on several systemic and ocular parameters, including choroidal thickness, which was assessed through optical coherence tomography angiography (OCTA), in glaucoma suspects. Materials and Methods: A total of 40 eyes from 20 glaucoma suspects without any systemic or ocular diseases were included in this prospective observational study. All the participants undertook the WDT, which required the drinking of 1 L of table water in 5 min. The outcome measures included IOP, systolic and diastolic blood pressure (SBP and DBP), mean arterial pressure (MAP), mean ocular perfusion pressure (MOPP), ocular pulse amplitude (OPA), and subfoveal and peripapillary choroidal thickness, which were assessed at baseline and at four 15 min intervals after the WDT. Generalized least squares models and mixed model analyses that take into account repeated measurements were used to assess the changes over time of these parameters. Results: All the ocular and systemic parameters showed statistically significant changes at all time points compared to baseline apart from choroidal thickness. The peak changes were an IOP of 20.1 mmHg versus 17.3 mmHg at 45 min, an SBP of 137.6 mmHg versus 125 mmHg at 30 min, a DBP of 95.9 mmHg versus 85.7 mmHg at 15 min, and an MOP of 53.51 mmHg versus 48.89 mmHg at 15 min. Conclusions: Despite elevations in IOP and significant changes in all the assessed systemic parameters, the WDT was not associated with changes in choroidal thickness in glaucoma suspects.

Investigation of the short-term effects of water drinking test on the eye using Optical Coherence Tomography Angiography in young healthy male subjects

PURPOSE

To evaluate the acute effects of the water drinking test (WDT) on the eye using optical coherence tomography angiography (OCTA) on healthy young male subjects.

METHODS

The study included 25 eyes of 25 male subjects. Selected parameters of the retinal vasculature were measured, including macular flow indices, foveal avascular zone, and vessel densities (VDs) of the macula using OCTA. The measurements were taken on the first day without drinking water at 0 min, 30 min and 60 min, then repeated on the second day before drinking water at 0 min, and after drinking water at 30 min and 60 min. The Paired Samples t-test and repeated measures One-way analysis of variance test were used in the statistical analyses.

RESULTS

The repeated measures analysis of variance test using Bonferroni adjustment demonstrated a significant increase in superficial and deep foveal VD following WDT (p <0.001 for both). Intraocular pressure, retinal nerve fiber layer thickness, foveal avascular zone, flow area of choriocapillaris, flow area of outer retina, foveal non-flow area of superficial layer, and retinal thickness measurements showed no significant changes following WDT.

CONCLUSIONS

WDT is associated with temporary flow modifications in superficial and deep foveal vascular plexus in young male subjects.

Hemoglobin Video Imaging Detects Differences in Aqueous Outflow Between Eyes With and Without Glaucoma During the Water Drinking Test

PRCIS

Hemoglobin video imaging (HVI) demonstrates increased aqueous outflow (AO) in response to the water drinking test (WDT) in patients with and without glaucoma. In glaucomatous eyes, increased AO was not sustained, and characteristic flow patterns were seen.

PURPOSE

To observe how variations in intraocular pressure (IOP) correlate with the flow of aqueous in episcleral veins.

DESIGN

Prospective observational cohort study.

PARTICIPANTS

The WDT increased AO into the episcleral venous system in 30 eyes recruited from Sydney Eye Hospital. A comparison was made between glaucomatous (n=20) and nonglaucomatous eyes (n=10).

METHODS

Each patient had baseline IOP and HVI before drinking 10 mL/kg body weight of water. IOP and HVI were then repeated every 15 minutes for 1 hour. Aqueous column cross-sectional area (AqCA) of the most prominent nasal and temporal aqueous veins was used to semi-quantify conventional AO.

MAIN OUTCOME MEASURES

Change in IOP and AqCA from baseline during the WDT. Aqueous flow characteristics were also observed.

RESULTS

Peak IOP elevation above baseline was significantly higher in the glaucoma group, with an average IOP rise of 39.7% on 1.6 1.1 medications, compared with 22.9% in the control group ( P =0.04). AqCA significantly increased for glaucomatous and nonglaucomatous eyes in response to water ingestion ( P <0.05). AqCA fell by 50% in glaucomatous eyes ( P =0.003) and 33% in nonglaucomatous eyes ( P =0.08) at study completion compared with the peak measurement. IOP remained >30% elevated in 8 glaucomatous eyes (40%) after 60 minutes and no control eyes. Variations in qualitative aqueous flow patterns were observed in glaucomatous eyes but not in controls.

CONCLUSIONS

AO volume, estimated by AqCA, increases in response to IOP elevation induced by an ingested water bolus in patients with and without glaucoma. The increase in aqueous drainage was not sustained in glaucomatous eyes and may have led to incomplete recovery of IOP. Using HVI in combination with the WDT may assist with clinical decision-making and facilitate the monitoring of responses to treatment.

CHOROIDAL CHANGES DUE TO LONG-TERM USE OF N95 FACE MASKS

PURPOSE

We aimed to examine the changes in choroidal stroma and vascular system due to long-term use of N95 mask in healthcare workers.

METHOD

The healthcare workers included in the study were between the ages of 18-50, with best corrected visual acuity (BCVA) 10/10, spherical and cylindrical refractive errors less than 3 diopters, intraocular pressures (IOP) within normal limits, and axial lengths (AL) less than 25 mm. The choroid was imaged with enhanced depth imaging (EDI) techniques using SD-OCT. The choroidal vascularity index (CVI), total choroidal area (TA), luminal area (LA), and stromal area (SA) were measured in the subfoveal 2 mm area. Measurements were first made after wearing the N95 mask for at least 2 hours without removing it and repeated 1hour after removing, while doing office working.

RESULTS

The study included 62 eyes from 62 participants (32 women [%51.61]; 30 men [%48.39]). The mean age of patients was 33.81± 8.88 years (20-50 years). The differences in subfoveal TA, LA, SA between 2 hours of N95 mask use and 1 hour after removal of the mask were statistically significant (p<0.05 for each). However, the difference in CVI between the mask use and removal of the mask was not statically significant (p=0.537) CONCLUSION: Due to CO2 retention and hemodynamıc changes, choroidal vascular flow, the choroidal vascular area, and the choroidal stromal area may be affected by prolonged use of masks.

Retinal microvascular density modifications during the water drinking test

PURPOSE

The water drinking test (WDT) is a well-known stress test that increases intraocular pressure (IOP) momentarily and can indicate risk of glaucoma progression. This study focuses on correlating changes in the retinal microvascular plexus with the WDT in young healthy subjects.

METHODS

A total of 20 eyes of 20 healthy young subjects (mean age 24.37 ± 2.17 years) were included in this study. In our protocol, WDT consisted of drinking 1 L of water within 5 min. Outcome measures in this prospective observational study were mean arterial pressure (MAP), heart rate (HR), IOP, and retinal vessel density of both superficial and deep macular retina using optical coherence tomography angiography (OCTA), which were assessed before water ingestion and four times after at 15-min intervals. OCTA images were later quantified by fractal analysis (box counting [D_box]). One-way repeated measures analysis of variance (ANOVA) was used to assess the effects of WDT on each of the parameters.

RESULTS

The WDT resulted in significant peak changes of the following parameters compared to baseline: IOP: 15.63 ± 3.37 versus 18.38 ± 4.53 mmHg at 30 min, p < 0.001; HR: 75.74 ± 12.23 versus 64.95 ± 11.37 bpm at 15 min, p < 0.001; deep retinal vessel density 1.758 ± 0.14 versus 1.749 ± 0.16 at 15 min, p = 0.040.

CONCLUSIONS

Besides IOP elevation and systemic effects in HR, WDT is associated with temporary modifications of the deep vascular plexus in young healthy subjects.

Study of choroidal thickness variations after ingestion of a taurine and caffeine-containing energy drink

BACKGROUND & AIMS

Choroidal thickness can undergo considerable variations in response to different substances. The aim of this study was to assess the change in choroidal thickness after the ingestion of taurine and caffeine contained in the Red Bull energy drink.

METHODS

Enhanced Depth Imaging - Spectral Domain Optical Coherence Tomography was used to measure subfoveal choroidal thickness (SFCT) variations in healthy volunteers at several time points after drinking a Red Bull can (25 cl).

RESULTS

Forty eyes of 20 volunteers were enrolled. A significant reduction in SFCT (-14 μm, p < 0.0001) occurred at 1 h after the Red Bull intake, and was even more important (-20.14 μm, p < 0.0001) in eyes with particularly thick choroids (≥ 395 μm). SFCT measurements at 4 h were comparable to baseline.

CONCLUSIONS

A concomitant ingestion of caffeine and taurine can induce a transient choroidal thinning that is more marked in eyes with thick choroids.

REGISTRATION NUMBER OF CLINICAL TRIAL

NCT02856256.

Changes in Choroidal Component Ratio and Circulation After Coffee Intake in Healthy Subjects

Purpose

The effects of coffee intake on the ratio of stromal and luminal components in the choroid and the underlying mechanism remain unclear. This prospective cross-sectional study aimed to explore how coffee intake affects the choroidal component ratio and circulation.

Methods

Forty-nine right eyes of healthy adult volunteers were evaluated as the coffee intake group. Thirty-two right eyes of healthy volunteers served as the control group. The participants consumed 185 mL of coffee or water, respectively, and the systemic hemodynamics, enhanced-depth imaging optical coherence tomographic (EDI-OCT) images, and foveal mean blur rate (MBR), an indicator of blood flow velocity, were recorded at baseline and after coffee or water intake. The EDI-OCT images were binarized using ImageJ software, and subfoveal choroidal thickness (SCT) and whole, luminal, and stromal choroidal areas were calculated.

Results

In the coffee intake group, significant decreases in SCT and luminal area peaked at 60 minutes after intake (both P < 0.001), whereas a significant increase in MBR peaked at 30 minutes (P < 0.001). No significant stromal area fluctuations were observed. SCT and luminal area fluctuations exhibited a significant positive correlation (r = 0.978, P < 0.001). Significant negative correlations of luminal area fluctuations with MBR fluctuations were observed by stepwise regression analysis (r = -0.220, P < 0.001). The control group exhibited no significant fluctuations.

Conclusions

Coffee-induced choroidal thinning may result mainly from a reduction in the choroidal vessel lumen, and this vessel lumen reduction correlated with an increased choroidal blood flow velocity after coffee intake. These coffee-induced changes in choroidal component ratio and circulation should be considered when evaluating choroids.

The effect of religious fasting and dehydration at Ramadan on choroidal thickness and Retinal vessel densities, measured with optical coherence tomography angiography

AIM

To investigate the effect of religious fasting and dehydration at Ramadan on choroidal thickness and vessel density in the superficial and deep vascular plexuses with OCTA.

METHODS

The choroidal thickness, and superficial and deep vessel density indices of fasting healthy subjects were measured with an OCTA device, and compared with non-fasting measurements.

RESULTS

The study included 70 eyes of 35 healthy subjects with a mean age of 42.86 ± 8.3 years. The measured choroidal thickness, superficial vessel density index and deep vessel density index were 288.89 ± 67 µm, 40.56% and 41.43%, respectively when measured in the fasting period, compared to 284.62 ± 65 µm, 40.41% and 41.41%, respectively when measured in the non-fasting period. The choroidal thickness under the fovea center was found to be significantly higher in the fasting period than in the non-fasting period (p = 0.014). The mean total choroidal thickness was found to be reduced in the non-fasting period, although not to a statistically significant degree (p > 0.05). An analysis of the mean total superficial and deep vascular plexuses revealed no statistically significant difference (p = 0.368, p = 0.938 respectively).

CONCLUSION

Although a significant increase was noted in central choroidal thickness in the fasting period, no significant change due to fasting was observed in the superficial and deep capillary plexuses. The choroidal layer may vary in thickness due to fasting-related metabolic factors, while retinal vessels are more stable against such effects.

Changes in choroidal structure following intravitreal aflibercept therapy for retinal vein occlusion

AIMS

To examine the choroidal change accompanying retinal vein occlusion (RVO) in detail, we measured changes in choroidal structure after intravitreal aflibercept (IVA) injections for RVO using binarisation of enhanced depth imaging optical coherence tomographic (EDI-OCT) images and assessed associations with clinical outcome.

METHODS

Retrospective, observational case series. Forty treatment-naïve patients (10 central, 18 major branch and 12 macular branch RVO) were examined by EDI-OCT before and 1, 3 and 6 months after IVA injections. EDI-OCT images were binarised using ImageJ. Subfoveal cross-sectional areas of the luminal, stromal and total choroid over a 1500 µm span were measured and the stromal area to total choroidal area (S/C) ratio was calculated.

RESULTS

Compared to normal contralateral eyes, afflicted eyes at baseline exhibited significantly greater stromal area (p<0.001), total choroidal area (p=0.001) and S/C ratio (p<0.001), but no difference in luminal area (p=0.083). The stromal area, S/C ratio and total choroidal area were significantly reduced in afflicted eyes at 1, 3 and 6 months after IVA (all p<0.006). Baseline S/C ratio was significantly correlated with baseline visual acuity (VA), baseline central retinal thickness (CRT) and VA and CRT improvement at 1, 3 and 6 months post-treatment even after adjusting for the axial length, age and sex (all p<0.012).

CONCLUSION

RVO induces substantial oedema of the choroidal stromal area that is detectable by binarisation of EDI-OCT images. This stromal oedema likely stems from high intraocular vascular endothelial growth factor levels. Changes in choroidal structure may be used to assess severity and prognosis of RVO.

Choroidal Vascularity Index: An In-Depth Analysis of This Novel Optical Coherence Tomography Parameter

Remarkable improvements in optical coherence tomography (OCT) technology have resulted in highly sophisticated, noninvasive machines allowing detailed and advanced morphological evaluation of all retinal and choroidal layers. Postproduction semiautomated imaging analysis with dedicated public-domain software allows precise quantitative analysis of binarized OCT images. In this regard, the choroidal vascularity index (CVI) is emerging as a new imaging tool for the measurement and analysis of the choroidal vascular system by quantifying both luminal and stromal choroidal components. Numerous reports have been published so far regarding CVI and its potential applications in healthy eyes as well as in the evaluation and management of several chorioretinal diseases. Current literature suggests that CVI has a lesser variability and is influenced by fewer physiologic factors as compared to choroidal thickness. It can be considered a relatively stable parameter for evaluating the changes in the choroidal vasculature. In this review, the principles and the applications of this advanced imaging modality for studying and understanding the contributing role of choroid in retinal and optic nerve diseases are discussed. Potential advances that may allow the widespread adoption of this tool in the routine clinical practice are also presented.