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A.G. Boehm, E. Schmidt, K. Loeffler, L.E. Pillunat; Measurement of peripapillary nerve fiber layer thickness in different distances to the optic nerve head with optical coherence tomography . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3316.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess which distance to the optic nerve head is most favorable for circular measurements of retinal nerve fiber layer thickness (RNFLT) with the OCT to detect differences between glaucoma and normal subjects. Methods: 98 eyes of 67 subjects (normal subjects and POAG patients) were examined by Stratus OCT (Zeiss, Model 3000, Software Version 2.0). Images were scanned in the "proportional circle" mode and analyzed with the "RNFL thickness analysis" protocol. Firstly a circular scan was approximated to the disc margin which was considered as the disc diameter. Circular scans with a diameter of the 1.4–fold, 1.8–fold, and 2.0–fold of the initial circular scan were taken. For each diameter 2 scans were measured consecutively within seconds and means were calculated. Decentered scans were not evaluated and repeated. If not all scans could be analyzed by the OCT software, subjects were excluded. For statistics the Friedman test and the Mann–Whitney U test with Bonferroni correction were used. Results: For 23 normal and 19 eyes of POAG patients a complete set of scans could be analyzed by the OCT software. Mean RNFLT was 140±31µm for the 1.0–fold of the disc diameter, 126±22µm for the 1.4–fold, 99±16µm for the 1.8–fold, and 87±14 µm for the 2.0–fold in the normal subjects, and 111±24 µm, 106±23 µm, 78±24 µm, and 79±18 µm in the glaucoma patients, respectively. RNFLT was statistically significant different in scan diameters in both groups (p=0.000). Differences between the groups were statistically significant for the 1.0–fold of the disc diameter (p=0.003), for the 1.4–fold (p=0.01), and for the 1.8–fold (p=0.002), but not for the 2.0–fold of the disc diameter (p=0.10). Conclusions:Circular scans with a 1–fold and with a 1.8–fold disc diameter seem to be able to differentiate best between glaucoma and normal subjects. As the circular scan directly at the disc margin is most vulnerable to potential decentration errors a 1.8–fold diameter seems to be most advantageous for the differentiation between normals and glaucoma. RNFLT decreases with increasing distance from the disc margin in normals and glaucoma.
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