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Monika Ewa Danielewska, Aleksandra Kicinska, Michal Marcin Placek, Katarzyna Lewczuk, Marek Rekas; Evaluation of spectral changes in corneal pulse signal following canaloplasty. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6202.
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© ARVO (1962-2015); The Authors (2016-present)
To ascertain whether spectral analysis of the corneal pulse (CP) signal provides supporting information for evaluating corneal biomechanics after canaloplasty.
Fifteen primary open-angle glaucoma (POAG) patients who underwent canaloplasty and phacoemulsification were enrolled in this study. Standard ophthalmological examination was performed before washout from antiglaucoma medications, at pre-operative stage (the day of surgery), 3, 6, and 12 months after surgery, including intraocular pressure measurement (IOP, Goldman). In addition, non-contact measurements of the CP signal were performed using an ultrasonic transducer. Raw CP signal was preprocessed and then amplitudes of its first three harmonics associated with the heart rate (ACP1, ACP2, ACP3) were estimated. Next, ACP2 and ACP3 were normalized to ACP1, giving ACP2n and ACP3n, respectively. Temporal changes of the considered parameters were tested using Wilcoxon signed rank test with Bonferroni corrected α = 0.005.
A decrease in ACP1 and an increase in ACP3n were observed between the pre-washout and the pre-operative stage (p = 0.0031 and p = 0.0038, respectively); see Fig.1. This corresponds to the increase in IOP values between those two stages, from 16.8 ± 2.7 mmHg (mean ± SD) to 22.1 ± 4.5 mmHg (p = 0.0044). After surgery, ACP3n reaches the highest value at 3 months post-operatively compared to the level recorded at pre-washout (p = 0.0045), and then significantly decreases at 12 months (p = 0.0045). At 12-month follow-up no patient required glaucoma medication.
Our study revealed that the spectral content of the CP signal carries, in an indirect way, information about both IOP variations and changes in corneal biomechanics after canaloplasty. Changes in ACP3n can reflect alterations in corneoscleral stiffness caused by surgery. In this sense, ACP3n can be viewed as an indirect supporting indicator for monitoring postoperative corneal biomechanical behavior and estimating the time at which measures of IOP will no longer be biased by the changed cornea boundary conditions caused by canaloplasty.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Boxplots of IOP (A), ACP1 (B), and ACP3n (C) at consecutive measurement stages; * indicates p < 0.005.
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