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C. Klatt, A. Bunse, H.C. Hasselbach, J. Roider; Accuracy of OCT –Maps and OCT –Scans in Age–Related Macular Degeneration (ARMD) and Diabetic Macular Edema (DME) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1552.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Optical coherence tomography (OCT) is a fast and noninvasive examination technique. This method is by now widely applied in the diagnosis macular diseases in everyday clinical routine and has become a standard for quantitatively monitoring retinal thickness in clinical trials. For this, analysis programs are employed that use an algorithm to create a topographic retinal map based on 6–24 radial scans crossing the macular region. The aim of this study is to calculate the accuracy of OCT –scans in ARMD and DME. Methods: This study involved 40 consecutive patients (mean 78.1 y) (40 eyes) with ARMD (5 classic choroidal neovascular membrane (CNVM), 35 occult CNVM) and 20 patients (mean 61.2 y) (20 eyes) with DME (16 focal–, 4 diffuse macular edema). In all these patients an OCT examination (Humphrey/Zeiss OCT III) with 6 radial scans was performed. In each patient, each single radial scan was evaluated to determine in what percentage of cases the program defined the space between internal limiting membrane and choriocapillary complex correctly. These results were compared to the topographical map as provided by the analysis program. Results: The A–scans accepted by the software were similar in both cases (98.5% ARMD vs. 98.8% DME). Detailed assessment showed that in only 1 of the 40 cases (2.5%) the analysis software had recognized all 6 scans correctly in ARMD. In 6 cases (15%) all 6 scans were misinterpreted by the system. On average 3.5 of 6 scans were not recognized correctly in ARMD. The mean variation of central retinal thickness as calculated by the single lines was 56.3 µm. In DME, the analysis software recognized in 15 of 20 cases (75%) all 6 scans correctly. Only in 1 patient were 2 scans not recognized correctly. On average 0.3 of 6 scans were misinterpreted. The mean variation of central retinal thickness as calculated by the single lines was 11.6 µm. Conclusions: OCT with automated fundus mapping programs is not suitable for monitoring retinal thickness in patients with ARMD. Due to the mean variation of about 60 µm in calculating retinal thickness in ARMD only higher changes can be detected reliable. In such patients, unlike in patients with DME, the analysis software is inaccurate in defining retinal boundaries for further analysis. This difference is highly significant (p < 0.05). Possible reasons for this may be the altered anatomical composition of the retina in patients with ARMD and a reduced ability of central fixation. A manual definition of the retinal boundaries by the operator, which could be helpful, is not yet available in the currently used software.
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