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Alberto Diniz-Filho, Fabio B Daga, Linda M Zangwill, Nara G. Ogata, Robert N Weinreb, Felipe Medeiros; Signal-to-Noise Ratio for Detection of Glaucoma Progression Using a Combined Index of Structure and Function. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5835.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the ability of a combined index of structure and function (RGC index) for detecting progression in glaucoma using a signal-to-noise ratio approach.
This was a prospective observational cohort study involving 642 eyes of 369 patients followed for an average period of 4.6 ± 1.0 years. Four hundred and seventy-five (74.0%) had a diagnosis of glaucoma and 167 (26.0%) were suspected of having the disease. All eyes underwent imaging using optical coherence tomography (OCT) along standard automated perimetry (SAP) with an average of 8.9 ± 2.5 tests. The RGC index combined OCT and SAP information and provided output on the estimated number of retinal ganglion cells in the eye. For each eye, ordinary least squares (OLS) linear regression models were used to regress SAP mean deviation (MD), spectral domain OCT global retinal nerve fiber layer (RNFL) thickness, and RGC index over time. The slopes of regression represented the signal. Standard deviations of residuals (SDres) were extracted from OLS linear regression to represent the expected variability estimates (‘noise’). The resulting signal-to-noise ratios were calculated for each eye by dividing the slope by SDres values for each eye and each parameter.
Average SAP MD at baseline was -3.1 ± 5.6 dB, whereas average OCT global RNFL thickness was 81.0 ± 16.8 μm. Average RGC index at baseline was 727,944 ± 244,044 cells. Average rates of change were -0.16 ± 0.53 dB/year, -0.46 ± 1.27 μm/year, and -13,211 ± 19,768 cells/year, respectively for SAP MD, OCT global RNFL thickness, and RGC index. Individual signal-to-noise ratios were significantly better for the RGC index (-0.49 year-1) as compared to SAP MD (-0.19 year-1; P<0.001) and OCT global RNFL thickness (-0.40 year-1; P<0.001).
Analysis of longitudinal signal-to-noise ratios demonstrated that a combined index of structure and function (RGC index) performed better than isolated global SAP and OCT parameters for detection of progression in glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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