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Pui-Yi Boey, Hongli Yang, Juan Reynaud, Stuart Keith Gardiner, Shaban Demirel, Brad Fortune, Christy A Hardin, Camila Zangalli, Claude Burgoyne; Optic Nerve Head (ONH) Neuroretinal Rim vs Retinal Nerve Fibre Layer Thickness (RNFLT) Change in Eyes with Glaucomatous Visual Field Change. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4025.
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© ARVO (1962-2015); The Authors (2016-present)
To compare spectral-domain optical coherence tomography (SDOCT) minimum rim width (MRW), minimum rim area (MRA) and RNFL thickness (RNFLT) rates of change in 71 subjects with evidence of glaucomatous visual field progression, using longitudinal signal-to-noise ratio (SNR) analysis.
Longitudinal (every 6 months for at least 6 scans) SDOCT (870 nm, Spectralis, Heidelberg Engineering) ONH (24 radial Bscans) and RNFLT circle scans from one eye each of 71 subjects were analyzed (from 227 within the Portland Progression Project) after being identified as the fastest visual field progressors (MD change; -2.23 to -0.04 dB/yr) over the same period. Within the ONH Bscans, Bruch’s membrane opening (BMO) and the internal limiting membrane (ILM) were segmented using Spectralis software, then hand corrected, allowing global MRW and MRA to be generated (Gardiner et al, AJO 2013, Epub). Circle scans were separately hand corrected before RNFLT was generated. Longitudinal SNRs, defined as the rate of change divided by the standard deviation of residuals from the trendline (Gardiner et al, TVST 2013), were calculated for MRW, MRA and RNFLT for each eye, assuming linear change over time.
Mean rates of change in these 71 eyes were -2.45 μm/yr for MRW, -10,027 μm2/yr for MRA, and -1.33 µm/yr for RNFLT. The 90th percentiles of the absolute rate of change were used, and longitudinal SNRs were -1.51/yr, -1.39/yr and -1.55/yr for MRW, MRA and RNFLT respectively. Longitudinal SNRs for MRA and RNFLT were significantly different (p=0.014, Wilcoxon rank sum test), whereas differences between MRW and MRA (p=0.42) or RNFLT (p=0.13) were not significant.
Among eyes showing visual field change, MRW and RNFLT demonstrate better longitudinal SNRs than MRA. SNR analysis may be useful in comparing ONH neuroretinal rim parameters and RNFLT change, as it overcomes differences in measurement units.
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