Purpose: To analyze the intra- and inter-observer reprodu-cibility of retinal fiber layer measurements. Methods: Twenty-six normal eyes underwent retinal nerve fiber layer thickness measurements with the GDx scanning system. Three images of each eye were taken by three different observers. For each case, each observer was asked to choose the best image and also to use the mean of the three images for each case. Comparisons were made using the best image and also the mean image provided by the software. The mean thickness values in each quadrant and their ratios were compared using Friedman rank analysis of variance. Results: The comparison of results obtained from the three images taken by the same observer (intraobserver reprodu-tibility) did not show any statistically significant difference. The analysis of the data by the R (resident), T (technician) and G (ophthalmologist specialized in glaucoma) observers revealed respective-ly: pR( S = 0.89; I = 0.24; T = 0.89; N = 0.30), pT( S = 0.76; I = 0.70; T = 0.22; N = 0.63), and pG( S = 0.48; I = 0.89; T = 0.30; N = 0.89). Regarding the isolated values (superior, inferior, temporal and nasal), the analysis of the results considering the values obtained from the mean image did not reveal a statistically significant difference between the three investigators. But when relationships were considered a statistically significant difference was observed regarding the superior/inferior ratio (p S/I = 0.037). Statistically significant differences were detected when considering the best image. Inferior and temporal mean thickness values were statistically different between observers (p = 0.04 and 0.003 respectively). Also, the superior/temporal (S/T), inferior/temporal (I/T), tem-poral/nasal (T/N) and superior/inferior (S/I) ratios showed statistically significant differences between observers (p S/T = 0.02; p I/T = 0.03; p T/N = 0.007; p S/I = 0.037). Conclusion: The results showed good reproducibility of the GDx Scanning System results using the mean image pro-vided by the equipment software.
GDx; Nerve fiber analyzer; Nerve fiber layer
