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Giacomo Calzetti, Nicola Ungaro, Luigi Varano, Giulia Gennari, Claudio Macaluso, Stefano A Gandolfi; Steady-state PERG after water drinking test in open angle glaucoma and normal subjects. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6406.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of water drinking test (WDT) on steady-state pattern electroretinogram (PERG) in open angle glaucoma (OAG) and in healthy subjects.Our initial hypothesis was that WDT could affect negatively PERG in glaucomatous patients.
Observational case-control study. 12 eyes of 8 OAG patients scheduled for a routine WDT and PERG evaluation with a visual field defect within stage 2 of the Glaucoma Staging System 2 (mean Standard Automated Perimetry-MD -1,62 ± 1,38 dB) and/or glaucomatous alteration of macular ganglion cell layer + inner plexiform layer thickness measured by Spectral Domain OCT, no prior ocular surgery or laser and no ocular disease besides OAG and 11 eyes of 6 age-matched normal controls (first-degree relatives of glaucomatous subjects undergoing a full list of examinations within a frame of a case-finding program) have been included. All of the subjects underwent PERG and intraocular pressure (IOP - by means of Goldmann applanation tonometry) recording before and 30 minutes after a WDT (1 liter of water in 10 minutes).PERG amplitudes and IOP before and after water intake were compared by means of Wilcoxon matched pairs test and paired Student t test, respectively, in both glaucomatous and controls.Changes in PERG amplitude and in IOP were correlated by means of Spearman rank correlation test, in both groups.
Mean baseline IOP values were 14,41 ± 2,53 mmHg in the OAG cohort and 12,45 ± 2,29 mmHg in the control cohort. After WDT mean IOP values were 19,25 ± 4,07 mmHg and 14,36 ± 2,54 mmHg, with statistically significant increase in both groups (P<0,0001 and P=0,0003, respectively).PERG amplitude showed a trend towards increase after WDT only in the OAG group (P=0,059 - median of amplitude values was 2,71 μV at baseline and 3,78 μV after WDT).A positive correlation between IOP changes and PERG amplitude changes was found in glaucomatous patients (r =0,9183, P<0,0001), while no correlation was found in healthy subjects.
Unexpectedly, we found a trend towards increase of PERG amplitude after WDT in patients with OAG. The most interesting finding is the positive correlation between changes in IOP and in PERG amplitude after water intake found in patients with OAG, but not in healthy subjects.We hypothesize that a common unknown factor, possibly vascular and linked to water intake, could cause both IOP and PERG amplitude increase in patients with OAG.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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