Reproducibility of intraocular pressure peak and fluctuation of the water-drinking test

The relationship between intraocular pressure and glaucoma: An evolving concept

Intraocular pressure (IOP) is the most important modifiable risk factor for glaucoma and fluctuates considerably within patients over short and long time periods. Our field's understanding of IOP has evolved considerably in recent years, driven by tonometric technologies with increasing accuracy, reproducibility, and temporal resolution that have refined our knowledge regarding the relationship between IOP and glaucoma risk and pathogenesis. The goal of this article is to review the published literature pertinent to the following points: 1) the factors that determine IOP in physiologic and pathologic states; 2) technologies for measuring IOP; 3) scientific and clinical rationale for measuring diverse IOP metrics in patients with glaucoma; 4) the impact and shortcomings of current standard-of-care IOP monitoring approaches; 5) recommendations for approaches to IOP monitoring that could improve patient outcomes; and 6) research questions that must be answered to improve our understanding of how IOP contributes to disease progression. Retrospective and prospective data, including that from landmark clinical trials, document greater IOP fluctuations in glaucomatous than healthy eyes, tendencies for maximal daily IOP to occur outside of office hours, and, in addition to mean and maximal IOP, an association between IOP fluctuation and glaucoma progression that is independent of mean in-office IOP. Ambulatory IOP monitoring, measuring IOP outside of office hours and at different times of day and night, provides clinicians with discrete data that could improve patient outcomes. Eye care clinicians treating glaucoma based on isolated in-office IOP measurements may make treatment decisions without fully capturing the entire IOP profile of an individual. Data linking home blood pressure monitors and home glucose sensors to dramatically improved outcomes for patients with systemic hypertension and diabetes and will be reviewed as they pertain to the question of whether ambulatory tonometry is positioned to do the same for glaucoma management. Prospective randomized controlled studies are warranted to determine whether remote tonometry-based glaucoma management might reduce vision loss and improve patient outcomes.

Association of Long-Term Intraocular Pressure Variability and Rate of Ganglion Complex Thinning in Patients With Glaucoma

PURPOSE

To evaluate the association of mean intraocular pressure (IOP) and IOP variability (IOP fluctuation [SD of IOP] and the IOP range) with the rate of ganglion cell complex (GCC) layer thinning over time in patients with glaucoma.

DESIGN

Prospective cohort study.

METHODS

Participants with at least 4 visits and 2 years of follow-up of optical coherence tomography tests were included. A linear mixed-effect model was used to investigate the association of IOP parameters with the rates of GCC thinning. Subgroup analyses were conducted for eyes with early (MD ≥ -6 dB), and moderate to advanced stage (MD < -6 dB) at baseline.

RESULTS

The cohort consisted of 369 eyes of 249 glaucoma patients (282 early glaucoma and 87 moderate to advanced glaucoma) with mean (standard deviation [SD]) age of 68.2 (10.7) years over 5.1 years of follow-up. The mean rate of GCC change was -0.59 (95% confidence interval [CI], -0.67 to -0.52) µm per year. In multivariable models, faster annual rate of GCC thinning was associated with a higher IOP fluctuation (-0.17 [95% CI, -0.23 to -0.11] µm per 1-mmHg higher, P < .001) or higher IOP range (-0.07 [95% CI, -0.09 to -0.05] µm per 1-mmHg higher, P < .001) after adjustment for mean IOP and other confounding factors. Similar results were found for early and moderate to advanced stages of glaucoma.

CONCLUSIONS

IOP variability showed an independent association with macular change in patients with glaucoma regardless of severity at baseline, even after adjustment for mean IOP, supporting its potential value as a therapeutic target for clinical decision-making.

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.

Imaging of aqueous outflow in health and glaucoma. Justifying the re-direction of aqueous

A wave of less invasive surgical options that target or bypass the conventional aqueous outflow system has been incorporated into routine clinical practice to mitigate surgical risks associated with traditional glaucoma drainage surgery. A blanket surgical approach for open-angle glaucoma is unlikely to achieve the desired IOP reduction in an efficient or economical way. Developing a precise approach to selecting the most appropriate surgical tool for each patient is dependent upon understanding the complexities of the aqueous outflow system and how devices influence aqueous drainage. However, homoeostatic control of aqueous outflow in health and glaucoma remains poorly understood. Emerging imaging techniques have provided an opportunity to study aqueous outflow responses non-invasively in clinic settings. Haemoglobin Video Imaging (HVI) studies have demonstrated different patterns of aqueous outflow within the episcleral venous system in normal and glaucomatous eyes, as well as perioperatively after trabecular bypass surgery. Explanations for aqueous outflow patterns remain speculative until direct correlation with findings from Schlemm's canal and the trabecular meshwork are possible. The redirection of aqueous via targeted stent placement may only be justifiable once the role of the aqueous outflow system in IOP homoeostasis has been defined.

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.

Intraocular Peak Pressure in Patients under Treatment with Fixed Combination of Bimatoprost/ Timolol/ Brimonidine once Daily versus Twice Daily

PRECIS

We investigate the efficacy of triple-fixed-combination of Bimatoprost/Brimonidine/Timolol once and twice a day, demonstrating higher intraocular pressure reduction with once-a-day use, and discuss possible implications based on previous literature.

PURPOSE

To compare the efficacy of fixed combination bimatoprost-timolol-brimonidine (Triplenex ®) instilled once-daily with twice-daily in primary open-angle glaucoma.

PATIENTS AND METHODS

Randomized clinical trial at a public eye care institution. Thirty patients with primary open-angle glaucoma were followed-up for three-months. The right and left eyes of these patients were randomly assigned to once-daily, (10:00 PM) or twice-daily, (10:00 AM; 10:00 PM) regimens of fixed combination bimatoprost-timolol-brimonidine. Intraocular pressure peaks were obtained with the water drinking test before the introduction of this medication (basal WDT0), one month (WDT 1), 2 months (WDT2) and 3 months (WDT3) after starting the use of the fixed combination of Bimatoprost/ Timolol/ Brimonidine (Triplenex®). Variation from peak intraocular pressure at WDT3 to peak at WDT0 was compared within groups of two versus once daily regimen.

RESULTS

Sixty eyes of 30 patients (age 70.67±9.70▒y) were included in this study. Baseline clinical characteristics were comparable between groups. Mean reduction in peak intraocular pressure from WDT0 to WDT3 was 6.1±6.1▒mmHg (30.5%) in the eyes receiving one drop per day and 4.3 ±5.7▒mmHg (21.5%) in the eyes receiving two drops per day (P=0.023). Mean reduction in peak intraocular pressure considering all WDT was also higher in the group with once-a-day treatment (5.90±6.03▒mmHg vs. 4.46±4.28▒mmHg, P=0.006).

CONCLUSION

Fixed combination of bimatoprost 0.01%, brimonidine tartrate 0.15% and timolol maleate 0.5% once-a-day is more effective in reducing peak intraocular pressure as measured by the WDT than twice-a-day dosing.

Effects of water drinking on corneal biomechanics: The association with intraocular pressure changes

Purpose:

We aimed to assess the impact of drinking water (500 and 1000 mL) on corneal biomechanics and determine the level of association between changes in intraocular pressure and variations in the different biomechanical properties of the cornea.

Methods:

A total of 39 healthy young adults ingested either 1000 mL (n = 21) or 500 mL (n = 18) of tap water in 5 min. The CorVis ST system was used to assess corneal biomechanics at baseline and at 15, 30, and 45 min after water ingestion.

Results:

Water drinking induced statistically significant changes in the deformation amplitude (P < 0.001, η² = 0.166), highest concavity time (P = 0.012, η² = 0.093), peak distance (P < 0.001, η² = 0.171), time and velocity of the first applanation (P < 0.001, η² = 0.288 and P = 0.016, η² = 0.087, respectively), and time and velocity of the second applanation (P = 0.030, η² = 0.074 and P = 0.001, η² = 0.132, respectively), being independent of the amount of water ingested (P > 0.05 in all cases). There were significant associations between changes in intraocular pressure and some parameters of corneal biomechanics

Conclusion:

Small variations in whole-body hydration status alter different biomechanical properties of the cornea, with these changes being associated with intraocular pressure levels. These findings indicate that whole-body hydration status can be considered for the diagnosis and management of different ocular conditions.

Duration of the hypotensive effect of prostaglandin analogues measured with the water drinking test in glaucoma patients

OBJECTIVE

To measure the magnitude and duration of the hypotensive effect of two prostaglandin analogues in glaucoma patients using the water drinking test (WDT).

METHODS

Patients received latanoprost or travoprost every 24 h and then every 48 h. Untreated WDT were performed at 7 am and with treatment 12, 36 and 44 h after the last dose; intraocular pressure (IOP) peak, fluctuation and the difference between peak and isolated IOP measurements at consultation times were calculated.

RESULTS

Forty-one eyes of 21 patients with primary open-angle glaucoma were included; 22 eyes received latanoprost, and 19 received travoprost. Mean untreated isolated IOP was 17.20 standard deviation (S.D.) 3.73 and 16.95 S.D. 2.61 mmHg and peak pressure 22.45 S.D. 2.91 and 21.58 S.D. 3.79 mmHg, for the latanoprost and travoprost groups, respectively. With treatment, peak pressure was reduced by 22.64% and 20.29% at 12 h, 18.44% and 14.64% at 36 h and 16.17% and 14.46% at 44 h, respectively. The fluctuation without treatment was 4.36 and 5.11 mmHg, and with treatment at 12 h was reduced to 2.77 and 2.89 mmHg, increasing again at 36 and 44 h.

CONCLUSIONS

A hypotensive effect was evident up to 44 h after the last dose of latanoprost and travoprost, similar for the two drugs and decreasing over time. IOP fluctuation was only reduced at 12 h.

Peak Intraocular Pressure Time during Water Drinking Test and Its Relationship with Glaucoma Severity

Purpose

To investigate the association between the time of occurrence of intraocular pressure (IOP) peaks during the water-drinking test (WDT) and visual field damage in a cohort of primary open-angle glaucoma (POAG) patients.

Methods

In this retrospective, cross-sectional study, 98 eyes from 49 consecutive POAG patients were followed in a referral clinical practice. The relationship between the time when IOP peaks occurred during the WDT and the visual field mean deviation (MD) assessed with 24-2 visual field was tested with mixed-effects models.

Results

MD value was significantly associated with the time of IOP peak occurrence (P = 0.020) when adjusting for the number of medications, but not with the IOP peak values (P = 0.238).

Conclusion

The time of IOP peaks occurrence during the WDT was associated with glaucoma severity among treated POAG patients.

Comparison of intraocular pressure peak and fluctuations among Filipino patients with non-glaucomatous eyes and glaucoma suspects using water drinking test and diurnal intraocular pressure

AIM

To compare the intraocular pressure (IOP) peaks and fluctuations using water drinking tests (WDTs) and mean diurnal IOP among Filipino patients with normal eyes and glaucoma suspects.

METHODS

This prospective study included normal and glaucoma suspect patients. Each patient underwent both WDT and mean diurnal examination on separate visits. For mean diurnal examination, IOP was recorded every 2h for 8h while in WDT, IOP was recorded prior to WDT, and post-WDT at 5, 15, 30, 45, and 60min. IOP peak was recorded as the highest IOP for both methods, and IOP fluctuation was recorded as highest IOP minus lowest IOP.

RESULTS

With the comparison of diagnostic tests, both normal eyes and glaucoma suspect groups, the peak IOP was caught at 15min. Comparative analysis of both groups also showed that the peak IOP measurements were statistically higher for the WDT compared to mean diurnal IOP (P=0.039, P=0.048 under normal group and P=0.032 and P=0.031 under glaucoma suspect group). Similarly, the WDT had a statistically higher mean IOP fluctuation score than the mean diurnal IOP method in both groups (P=0.003, P=0.011 under normal group; P=0.002 and P=0.005 under glaucoma suspect group).

CONCLUSION

This study shows that WDT is a comparable diagnostic exam in predicting IOP fluctuations than mean diurnal measurement. WDT is a promising diagnostic procedure for risk assessment in glaucoma.

Comparison of intraocular pressure variability detected by day diurnal variation to that evoked by water drinking

Purpose

To determine correlation and agreement between intraocular pressure (IOP) peak and fluctuations detected by day diurnal variation (day DVT) to that after the water-drinking test (WDT).

Methods

Patients (18-80 years) with glaucoma, suspects, and ocular hypertension (OHT) were enrolled. IOP readings were taken on applanation tonometer, at 2-h intervals, from 8 AM to 3 PM (DVT). 3 PM IOP served as WDT baseline. Patients consumed water (10 mL/kg) in 5-15 min, at 3 PM, after they fluid fasted for 2 h. IOP was recorded every 15 min, from 3.30 to 4.30 PM.

Results

A total of 200 eyes (100 patients) were included. 58.5% were established glaucoma, 32% suspects, 9.5% OHT. Correlation between mean and peak IOP by WDT and day DVT was strong and significant (r = 0.89, P < 0.00; r = 0.73, P < 0.00) while it was weak for fluctuation (r = 0.12, P < 0.07). Agreement on Bland and Altman plots was limited for mean IOP and poor for peak and fluctuations.

Conclusion

An exaggerated WDT response may indicate a compromised outflow facility and warrant close patient monitoring but the WDT cannot substitute day DVT in our clinical practice.

Correlation between intraocular pressure obtained with water drinking test versus modified diurnal tension curve measurement in pseudoexfoliation glaucoma

PURPOSE

The aim of this paper was to study the correlation and agreement between the intraocular pressure (IOP) peak value and fluctuations detected with the modified diurnal tension curve (mDTC) and the water drinking test (WDT) in pseudoexfoliation glaucoma (XFG) patients.

METHODS

This prospective observational study enrolled 42 eyes of 42 XFG patients. The IOPs were measured at 2-h intervals from 8 am to 4 pm with a Goldmann applanation tonometer by a single observer to establish the mDTC. The WDT was then performed between 4 and 5 pm on the same day and the IOP was measured 4 times at 15-min intervals after water ingestion. The IOP_peak, IOP_mean, IO _min, and IOP_fluctuation were measured with both the mDTC and WDT. The paired sample t test, Spearman's correlation coefficient and Bland-Altman plots were used for statistical analysis.

RESULTS

The mean age of the 42 patients consisting of 24 females and 18 males was 66.9 ± 6.8 years, and the mean central corneal thickness was 517.7 ± 29.1 µm. The mean values with the mDTC and WDT measurements were 15.05 ± 2.75 mmHg and 17.17 ± 3.25 mmHg (p ≤ 0.0001, r = 0.884) for IOP_mean, 16.76 ± 3.45 mmHg and 18.92 ± 3.94 mmHg (p ≤ 0.0001, r=0.787) for IOP_peak, and 13.61 ± 2.56 mmHg and 15.11 ± 2.84 mmHg (p ≤ 0.0001, r=0.824) for IOP_min, respectively, and a positive correlation was present between these values.

CONCLUSION

There was a positive correlation between the peak, minimum, and mean IOP values determined using the mDTC and WDT in treated XFG patients. WDT can be used as an alternative in the assessment of the IOP in these patients as a more practical method.

Correlation and Agreement Between Water Drinking Test and Modified Diurnal Tension Curve in Untreated Glaucoma Patients in Nigeria

PURPOSE

To determine the correlation and agreement between intraocular pressure (IOP) parameters evaluated by the modified diurnal tension curve (mDTC) and the water drinking test (WDT) in primary open-angle glaucoma (POAG) in an indigenous African population.

MATERIALS AND METHODS

This was a prospective, interventional, comparative study of 50 newly diagnosed, previously untreated primary open-angle glaucoma patients at the out-patient clinic of the Eleta Eye Institute, Ibadan. A series of IOP measurements were taken 2 hourly (from 7:00 AM to 3:00 PM) for the mDTC, using Goldmann applanation tonometer. The WDT was performed thereafter. The patients drank 800 mL of water within 5 minutes, and another series of IOP measurements were taken every 15 minutes for a duration of 1 hour from the moment water was fully ingested. Both the mDTC and the WDT were performed on the same day. IOP peak, mean, and IOP fluctuations were estimated from the data collected. Comparison between the mDTC and the WDT was performed using the paired Student T test for means, Pearson correlation analysis for correlation, and Bland-Altman analysis for agreement.

RESULTS

Estimated IOP parameters were significantly higher for the WDT than for the mDTC. The average peak IOP was 27.8±4.0 mm Hg during the WDT and 24.9±3.1 mm Hg during the mDTC (P<0.001). The average mean IOP was 25.8±3.6 mm Hg during the WDT and 22.3±2.4 mm Hg during the mDTC (P<0.001). The average IOP fluctuation was higher (6.6±2.9 mm Hg) during the WDT compared with 4.7±2.0 mm Hg during the mDTC. The mean and peak IOPs were strongly correlated between the mDTC (r=0.729, P<0.001) and the WDT (r=0.658, P<0.001). IOP fluctuation, however, showed weak correlation between the mDTC and the WDT (r=0.258, P=0.709).

CONCLUSIONS

There is a strong positive correlation between IOP parameters (peak and mean IOP) estimated from the WDT and the mDTC. The peak and mean IOP can be estimated from the WDT, which is quicker, compared with the mDTC. This is more relevant in low resource settings with limited personnel, time, and resource constraints. In addition, higher IOP values were obtained from the WDT compared with the mDTC, and therefore could serve as a useful practical way to determine target peak in order to optimize IOP control in glaucoma patients.

Role of the water-drinking test in medically treated primary open angle glaucoma patients

PURPOSE

The water-drinking test (WDT) has recently re-emerged as a possible way to determine the competency of the trabecular meshwork. We performed a prospective interventional study to test the hypothesis that the WDT could be useful in assessing fluctuations in patients undergoing treatment for primary open angle glaucoma (POAG).

METHODS

We included 122 patients; 62 on medical treatment for POAG (n=123 eyes) and 60 controls (n=120 eyes). The study group had been on intraocular pressures (IOP) lowering treatment continuously for at least 3months with stable IOP. The WDT was performed during fasting and was considered positive if it fluctuated ≥6mmHg.

RESULTS

The patients on medical treatment had a mean age of 50.56±18.45 years vs. 51.35±11.22 for the controls (P=0.34); with 71% being female in the study group and 77% in the control group. In the study group; 52% were on beta blockers (n=64), 27% combination of two or more medications (n=33), 19% prostaglandin analogues (n=24) and 2% alpha agonists (n=2). The WDT was positive in 17.07% (n=21) in the study group and 2.5% (n=3) in the control group (P=0.0001). The mean fluctuation was 7.14±2.15mmHg in the study group and 6.00±0mmHg in the controls (P=0.33). A positive WDT was found in 33.33% (n=11) of those on combination therapy; 12.5% (n=3) prostaglandin analogues and 10.94% (n=7) beta blockers (P=0.03). Combination therapy had the highest positive WDT fluctuation (7.54±2.87) followed by prostaglandin analogues (7.00±1.00) and beta blockers (6.57±0.78) with a P value of 0.44.

CONCLUSIONS

The WDT can identify significant fluctuations in eyes with POAG that are medically treated.

Results for Water-drinking Test, before and after Laser Iridotomy, in Primary Angle-closure Suspects

SIGNIFICANCE

Intraocular pressure and ocular biometric changes were similar before and after laser iridotomy in response to the water-drinking test in a cohort of patients at risk of angle closure. The water-drinking test does not seem to be a good provocative test to determine which eyes would benefit from a laser iridotomy. Our data call into question the preoperative predictive value of this test.

PURPOSE

The aim of this study was to evaluate the effect of water-drinking test on intraocular pressure and ocular biometric parameters, before and after laser peripheral iridotomy, in patients with an occludable angle.

METHODS

Twenty-seven patients, who met the inclusion criteria and had at least 180 degrees of iridotrabecular apposition, underwent a complete eye examination followed by the measurement of ocular biometric (using LenStar LS-900; Haag-Streit AG, Koeniz, Switzerland) and anterior chamber parameters (using Pentacam HR; Oculus Optikgerate GmbH, Wetzlar, Germany). All the measurements were repeated 30 minutes after the water-drinking test. Two weeks after laser peripheral iridotomy, all the measurements were repeated both before and after the water-drinking test.

RESULTS

The mean ± SD of the age of the participants was 57 ± 9 years, and 23 (85.2%) were male. Intraocular pressure increased after the water-drinking test in both pre-laser peripheral iridotomy (17.0 vs. 19.3 mmHg, P < .001) and post-laser peripheral iridotomy (15.6 vs. 18.6 mmHg, P < .001) conditions. The thickness values of central cornea increased slightly after the water-drinking test in pre-laser peripheral iridotomy (535 vs. 538 μm, P = .001) compared with post-laser peripheral iridotomy (532 vs. 536 μm, P = .003). The water-drinking test had no significant effect on other biometric or anterior chamber parameters, before or after laser peripheral iridotomy.

CONCLUSIONS

The water-drinking test increased intraocular pressure, both before and after laser peripheral iridotomy. Laser peripheral iridotomy had no significant effect on the amount of intraocular pressure change after the water-drinking test. The water-drinking test has no effect on other biometric or anterior chamber parameters.

Applications of the water drinking test in glaucoma management

Intraocular pressure (IOP) peaks and means have been considered important factors for glaucoma onset and progression. However, peak IOP detection depends only on appropriated IOP checks at office visits, whereas the mean IOP requires longitudinal IOP data collection and may be affected by the interval between visits. Also, IOP peak assessment is necessary to verify if the peak pressure of a given patient is in target range, to evaluate glaucoma suspect risk, the efficacy of hypotensive drugs and to detect early loss of IOP control. The water-drinking test has gained significant attention in recent years as an important tool to evaluate IOP peaks and instability. The main objective of this review was to present new findings and to discuss the applicability of the water-drinking test in glaucoma management.

Reproducibility of the water-drinking test in patients with exfoliation syndrome and exfoliative glaucoma

PURPOSE

To evaluate the reproducibility of intraocular pressure (IOP) peaks and fluctuations detected during the water-drinking test (WDT) in patients with exfoliation syndrome (XFS) and exfoliative glaucoma (XFG).

METHODS

This prospective study included 34 XFS and 30 XFG patients. Each patient was evaluated twice, with the two WDTs performed on a 30-day interval. We recorded IOP peak (highest IOP during the WDT) and IOP fluctuation (IOP peak minus IOP before the test). Bland-Altman analysis was applied to assess the agreement of IOP peaks and fluctuations between the two consecutive visits. We defined reproducible as within 4 mmHg for IOP peak and within 2 mmHg for IOP fluctuation.

RESULTS

There were no significant differences in IOP values, IOP peaks and IOP fluctuations between the two visits for both XFS and XFG patients (p > 0.05, for all). The coefficient of repeatability for IOP peak was 2.5 mmHg and 3.5 mmHg in XFS and XFG patients respectively and for IOP fluctuation, it was 2.1 mmHg and 2.2 mmHg. None of the XFS or XFG patients had an IOP peak difference higher than 4 mmHg. Intraocular pressure (IOP) fluctuation differences above 2.0 mmHg were found in 8.8% of XFS patients and 16.6% of XFG patients.

CONCLUSIONS

Intraocular pressure (IOP) peak and IOP fluctuation have a reproducibility, both in XFS and in XFG.

Intraocular pressure dynamics with prostaglandin analogs: a clinical application of the water-drinking test

AIM

To evaluate the clinical applicability of the water-drinking test in treatment-naive primary open-angle glaucoma patients.

METHODS

Twenty newly diagnosed primary open-angle glaucoma patients and 20 healthy controls were enrolled in this prospective study. The water-drinking test was performed at baseline and 6 weeks and 3 months after prostaglandin analog treatment. Peak and fluctuation of intraocular pressure (IOP) measurements obtained with the water-drinking test during follow-up were analyzed. Analysis of variance for repeated measures and paired and unpaired t-tests were used for statistical analysis.

RESULTS

The mean baseline IOP values in patients with primary open-angle glaucoma were 25.1±4.6 mmHg before prostaglandin analog treatment, 19.8±3.7 mmHg at week 6, and 17.9±2.2 mmHg at month 3 after treatment. The difference in mean baseline IOP of the water-drinking tests was statistically significant (P<0.001). At 6 weeks of prostaglandin analog treatment, two patients had high peak and fluctuation of IOP measurements despite a reduction in baseline IOP. After modifying treatment, patients had lower peak and fluctuation of IOP values at month 3 of the study.

CONCLUSION

Peak and fluctuation of IOP in response to the water-drinking test were lower with prostaglandin analogs compared with before medication. The water-drinking test can represent an additional benefit in the management of glaucoma patients, especially by detecting higher peak and fluctuation of IOP values despite a reduced mean IOP. Therefore, it could be helpful as a supplementary method in monitoring IOP in the clinical practice.

Selective Laser Trabeculoplasty Reduces Intraocular Pressure Peak in Response to the Water Drinking Test

PURPOSE

To determine the effect of selective laser trabeculoplasty (SLT) on intraocular pressure (IOP) peak and fluctuation induced by the water drinking test (WDT) in patients with open-angle glaucoma and ocular hypertension.

METHODS

Patients with open-angle glaucoma or ocular hypertension underwent the WDT before and after SLT within a 12-month period. No other changes to therapeutic regimen were permitted. IOP was measured with a Goldmann applanation tonometer at baseline and every 15 minutes for 45 minutes following a fluid challenge of 800 mL over 15 minutes. Baseline, peak, and percentage fluctuation in IOP from baseline were compared using a repeated measures analysis of variance with Bonferroni adjustment.

RESULTS

Twenty eyes from 20 patients were included in this study. The median patient age was 73±15 years (interquartile range) and 70% of patients were female. Ten eyes (50%) had a diagnosis of primary open-angle glaucoma and 10 eyes had ocular hypertension. Following SLT there was a statistically significant reduction in mean baseline IOP from 16.9±2.4 to 14.2±2.3 mm Hg (P<0.001), peak IOP from 21.9±3.7 to 16.9±3.1 mm Hg (P<0.001).

CONCLUSIONS

Patients with open-angle glaucoma and ocular hypertension treated with SLT have significantly reduced peak IOPs and fluctuation in IOP in response to the WDT.

Reproducibility of the water drinking test in treated glaucomatous patients

BACKGROUND

To evaluate the reproducibility of intraocular pressure peaks and fluctuation elicited during the water drinking test in treated glaucomatous patients with a long follow-up interval.

DESIGN

Retrospective cohort study in a tertiary care practice.

PARTICIPANTS

Thirty-four treated primary open-angle glaucoma patients.

METHODS

All patients underwent the water drinking test performed in two consecutive visits without any change in the therapeutic regimen. The mean interval between tests was 4.85 (range: 3-6) months. Reproducibility of peak and fluctuation during the water drinking test was assessed using intraclass correlation coefficients. Bland-Altman analysis was used to assess the agreement of intraocular pressure peaks and fluctuation measured between two consecutive tests.

MAIN OUTCOME MEASURES

Intraclass correlation and agreement of intraocular pressure peaks and fluctuation between visits.

RESULTS

There were no significant differences in baseline intraocular pressure values (mean ± standard deviation, 11.73 ± 2.36 and 11.61 ± 2.71 mmHg; P = 0.72) and peaks (14.55 ± 3.41 and 15.02 ± 3.66 mmHg, respectively; P = 0.163) detected during the water drinking test between the first and second visits. There was also no significant difference between the average intraocular pressure fluctuation values (2.82 ± 1.99 and 3.41 ± 2.54 mmHg, respectively; P = 0.135). Intraocular pressure peaks and fluctuation presented intraclass correlation coefficients of 0.85 (P < 0.001) and 0.50 (P < 0.001), respectively.

CONCLUSIONS

Our results demonstrate excellent reproducibility of intraocular pressure peaks during the water drinking test. Intraocular pressure fluctuation did not reveal good reproducibility, though. These results emphasize the applicability of this test to assess treatment efficacy in daily practice and interventional studies.