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CV Bunce, S De Cilla, DF Garway-Heath; A Comparison of Nerve Fibre Layer Measurements using Optical Coherence Tomography and Scanning Laser Polarimetry in Normal and Glaucomatous Eyes . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1004.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess agreement between two techniques of retinal nerve fibre layer measurement: scanning laser polarimetry (GDx) and optical coherence tomography (OCT) in a group of normal and glaucomatous eyes. Methods: Retinal nerve fibre layer thicknesses were obtained on a group of 24 subjects (10 normal, 14 with glaucoma) using GDx and OCT. Paired Student’s t-tests were conducted to examine evidence of systematic bias between the two techniques. Bland-Altman plots were constructed to assess whether agreement between the two methods depended upon the thickness of the nerve fibre layer. Comparisons were made in quadrant sectors and globally. Linear regression was employed to describe the relationship between OCT and GDx measures. Results: We found strong evidence of bias between the two techniques globally (P < 0.001) and in each sector (P <= 0.02) other than the temporal. These data provide evidence too that the difference between the methods depended upon the thickness of the nerve fibre layer. For a thin nerve fibre layer, OCT readings were lower than GDx measures whilst the reverse was seen for a thick nerve fibre layer. A linear regression of global differences of OCT and GDx against their average yielded the equation: OCT - GDx measure = 1.85 * average nerve fibre thickness - 103.1 (adj R(sq) = 0.87). Conclusion: These data suggest that there is disagreement between the measurements of nerve fibre layer thickness obtained using OCT and GDx. We have, however, derived an equation which relates these measures by the two techniques.
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