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R. Raut, A. Fansi, P. Harasymowycz; The Effect of Optic Disc Area, Axial Length and Refractive Error on RNFL Thickness as Measured by OCT III . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3660.
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© ARVO (1962-2015); The Authors (2016-present)
To study the influence of anatomic variations in optic disc area, axial length and refractive error on RNFL thickness as measured by OCT III.
109 non–dilated eyes of 55 subjects were scanned as part of a glaucoma screening study. IOL Master was used to measure axial length and refractive error. OCT III scans were used to measure optic disc area (Optic Nerve Head Analysis) and average Fast–RNFL thickness with concentric circles of 9,425mm and 10,87mm in length around the disc. Scans with a signal to noise ratio below 6 were excluded from analysis. Statistical tests including T–tests, Pearson correlation coefficients, and linear regression were performed.
No significant correlations were found between RNFL thickness and axial length (r2<0.05), between RNFL thickness and refractive error (r2<0.01) or between RNFL thickness and optic disc area (r2<0.05). Table 1 lists the number of measures and correlations. A statistically significant difference (two tailed student t test p = 0,0003) was found, however, between the RNFL thickness values measured at 9,425mm (n = 80 mean of 106,8 ± 16,0) and 10,87mm (n = 65 mean of 97,8 ± 12,8), indicating thinner RNFL measurements further away from the optic disc.
In this study, RNFL thickness as measured by OCT III. was found to be thicker adjacent to the optic disc rim margin and thinner outwards, with subjects having on average a thinner RNFL with the 10,87mm scan circle versus the 9,425mm one. No correlations, however, were found between RNFL thickness with optic disc area, axial length and refractive error. These anatomic differences must be considered when interpreting OCT III findings in clinical situations..
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