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P. G. Schlottmann, E. T. White, M. D'Eramo, D. F. Garway-Heath; Test Retest Variability of Rnfl Thickness Measurements With Stratus Oct in Normal and Glaucomatous Subjects. Invest. Ophthalmol. Vis. Sci. 2007;48(13):518.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the test re-test variability of the retinal nerve fibre layer (RNFL) thickness in normal and glaucomatous subjects as measured by Stratus OCT.
21 subjects (14 normal, 7 glaucomatous) were recruited for the study. Individuals underwent a complete ophthalmic examination and scanning with Stratus OCT. Measurements were acquired by two operators in two visits within 3 months. The fast RNFL 3.4 and standard RNFL 3.4 protocols were used. On the first session scanning followed the sequence: operator 1 (7 fast + 3 standard scans) - operator 2 (3 fast + 3 standard) - operator 1 (3 fast + 3 standard). On the second visit the sequence was operator 1 (3 fast + 3 standard) - operator 2 (7 fast + 3 standard). On the first visit the scanning circle was centred on the optic disc with the landmark placed on the temporal edge of the disc. On all subsequent scans the repeat function was used by both operators. All subjects had a visual acuity of 6/9 or better. The RNFL Average protocol was used to analyse scans. Reproducibility was evaluated by means of Bland Altman plots.
Of 21 subjects, 2 were unable to complete the study through unavailability or poor scan quality. Four normal subjects were excluded from analysis due to poor algorithm confidence (<7) in some scans. 9 normal subjects and 6 glaucomatous subjects were included for analysis. Subject age (years): normal, mean 67 (range 50-80), glaucoma, mean 73 (range 67-81). RNFL thickness (microns): normal = mean 97.6 (76.88 to 117.56), glaucoma = mean 63.9 (43.36 to 84.95). Visual field MD (dB): normal = mean 0.46 (-1.00 to 2.75), glaucoma = mean -3.57 (-12.44 to -1.02).Mean differences (95% limits of agreement)IAV: intra-visit; IAO: intra-operator; IEV: inter-visit; IEO: inter-operator; F: fast protocol; S: standard protocol
Mean differences were low across visits and operators. There were no significant differences in variability between normal or glaucomatous subjects. The limits of agreement appear to be narrower in the glaucomatous group with the ‘standard’ acquisition protocol. The higher scan density may reduce variability with a thinner RNFL.
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