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Editors Selection IGR 16-4
Clinical Examination Methods: Provocative tests
Comment by Remo Susanna Jr on:
55457 Rise of intraocular pressure in a caffeine test versus the water drinking test in patients with glaucoma, Tran T; Niyadurupola N; O'Connor J et al., Clinical and Experimental Ophthalmology, 2014; 42: 427-432
It is well-established that a significant proportion of glaucoma patients continue to develop progressive optic nerve damage and visual field loss despite apparent adequate control of IOP. This is thought to be due to IOP variations and IOP peaks not detected during routine clinical practice. There is a need to find tests that can detect IOP spikes not detected during clinical practice.The current study by Tran et al. is prospective, observermasked, cross-over and the aim is to verify if in cases where the WDT may not be tolerated or appropriate, such as in renal impairment or congestive heart failure, this test could be replaced by the caffeine test. Both tests increase the IOP, however, raising IOP is not sufficient for a test be applied into clinical practice.
To be clinically relevant a test must have some characteristics. The IOP peak elicited by WDT correlates with the magnitude of the damage and evaluates the ability of the eye to recover from IOP elevation.1 It correlates with visual field progression in glaucoma,2 and with clinical IOP measurements.3-5 Also it is reproducible.
The authors point out that when comparing the effect of IOP between the WDT and the CT at corresponding time points there was no statistically significant difference in IOP at baseline, 15 min and 30 min although the IOP elevation during the WDT in this period was twice greater than the IOP elevation during the CT. The authors should comment if the power of the sample would allow detecting such difference (only 14 eyes). However, at 45 min, the WDT had a statistically significant greater IOP increase (mean 3,2 mmHg) compared with the CT as the peak of the WDT did occur at that period of time. It is important to notice that the WDT has also been shown to detect more IOP peaks and with higher levels than modified diurnal tension curve, as stated by the authors. Although the IOP peaks in the WDT had a significant positive correlation with IOP peaks measured with those seen in the 24 h IOP this correlation was only fair, as the IOP peaks measured during 24-H in supine position was higher than the IOP peak elicited by the WDT.7
Finally, it has been suggested that expansion of choroidal volume may have a large contribution in IOP elevation during the WDT. Two recent studies evaluated CT changes during the WDT using OCT: Arora et al.8 studied CT changes in a group of patients with openangle and angle-closure glaucoma and Mansouri et al.9 evaluated the choroidal thickness changes after the WDT in healthy individuals. According to these authors, the fact that IOP increases without a commensurate choroidal thickness increase in open angle glaucoma supports the hypothesis that increased outflow resistance is the general mechanism of IOP rise after WDT.
The authors should be congratulated by this well-written study with the aim to find a substitute test for detecting IOP spikes out of office hours that has been shown important in the progression of glaucoma.
References
- Malerbi FK, Hatanaka M, Vessani RM, Susanna R, Jr. Intraocular pressure variability in patients who reached target intraocular pressure. Br J Ophthalmol 2005;89(5):540-542. Evaluate the ability of recovery from IOP elevation.
- Susanna Jr. R, Vessani RM, Hatanaka M, et al. The relationship between IOP peak in the Water Drinking Test and Visual Field Progression in Glaucoma. Brit J Ophthalmol 2005;89:1298-1301.
- De Moraes CG, Furlanetto RL, Reis AS, Vegini F, Cavalcanti NF, Susanna R, Jr. Agreement between stress intraocular pressure and long-term intraocular pressure measurements in primary open angle glaucoma. Clin Exper Ophthalmol 2009;37(3):270-274.
- Kumar RS. Does peak intraocular pressure measured by water drinking test reflect peak circadian levels? Clin Exper Ophthalmol 2008;36:312-315.
- Vasconcelos-Moraes CG, Susanna R, Jr. Correlation between the water drinking test and modified diurnal tension curve in untreated glaucomatous eyes. Clinics (Sao Paulo. 2008;63(4):433-436.
- Hatanaka M, Alencar LM, De Moraes CG, Susanna R. Reproducibility of intraocular pressure peak and fluctuation of the water drinking test. Clin Exper Ophthalmol. 2012.
- Sakata R, Aihara M, Murata H, et al. Intraocular pressure change over a habitual 24-hourperiod after changing posture or drinking water and related factors in normal tension glaucoma. Invest Ophthlmol Vis Sci 2013;54:5313-5320.
- Arora KS, Jefferys JL, Maul EA, Quigley HA. Choroidal thickness change after water drinking is greater in angle closure than in open angle eyes. Invest Ophthalmol Vis Sci 2012;53:6393-6402.
- Mansouri K, Medeiros FA, Marchase N, Tatham AJ, Auerbach D, Weinreb RN. Assessment of choroidal thickness and volume during the water drinking test by swept-source optical coherence tomography. Ophthalmology 2013;120(12):2508-2516.
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