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Navid Amini, Nila Cirineo, Sarah Nowroozizadeh, Sharon A Henry, Ted Chang, Thomas Chou, JoAnn A Giaconi, Joseph Caprioli, Kouros Nouri-Mahdavi; Influence of Disc-Fovea Angle Correction on Performance of SD-OCT RNFL Thickness Measurements. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4757. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the disc-fovea angle (DFA) inter-session measurement variability and explore DFA influence on SD-OCT retinal nerve fiber layer (RNFL) thickness measurement variability and its performance for detection of glaucoma.
58 normal subjects (108 eyes) and 51 patients (64 eyes) with perimetric glaucoma were prospectively recruited and underwent SD-OCT RNFL and macular imaging on Cirrus HD-OCT. The 200x200 RNFL thickness arrays were exported and custom software was used to interpolate RNFL thickness along a 3.46mm circle at one-degree intervals. DFA was measured on macular en face images with MATLAB. Coordinates of foveal and disc centers were found by fitting ellipses to foveal and disc margins. DFA measurements were repeated in 24 glaucoma eyes. Main outcome measures were magnitude of change in sectoral RNFL measurements, variability of sectoral RNFL measurements in normal subjects, structure-function relationships between clock hour sectors and Garway-Heath visual field clusters, and the ability to discriminate glaucoma from normal eyes (with ROC curves) before and after correction of RNFL measurements for DFA.
Average (SD) MD and DFA were -4.1 (3.3) and 0.1 (1.2) dB, and -6.7° (3.4°) and -7.9° (3.9°) in the control and glaucoma groups, respectively (p<0.001 and 0.039). The average difference in DFA repeat measurements was 2.0° (1.8°). For 58% of the eyes, the DFA measurement in the second visit was within 1.5° of the first visit. The average absolute change in sectoral RNFL thickness measurements was 6.1 (3.9) and 4.6 (3.1) µm in control and glaucoma subjects, respectively. The corrected RNFL measurements were thicker in clock hour sectors 2, 3, 7, 8, and 12 and thinner in the remaining sectors. The 95% prediction limits for sectoral RNFL thickness decreased in clock hour sectors 4, 5, 9, 10 and increased in 8 o’clock sector after correction for DFA (p<0.04). Regional structure-function relationships and discrimination ability of the sectoral RNFL measurements did not improve after correction for DFA (p>0.05 for all comparisons).
DFA measurements demonstrated good intersession repeatability. Although correction for DFA reduced measurement variability in some sectors in normal subjects, it did not enhance performance of the RNFL thickness for detection of glaucoma. Correction for DFA is not recommended for SD-OCT RNFL measurements.
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