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Delila Hodzic, Birgit Sander, Henrik Lund-Andersen; The effect of hard exudates and epiretinal fibrosis on the retinal thickness as calculated by optical coherence tomography (OCT) in diabetic macular edema. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4923.
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© ARVO (1962-2015); The Authors (2016-present)
Central retinal thickness and macular volume are major factors in the assessment and treatment of diabetic macular edema. OCT is used as a primary tool to objectively document and calculate retinal thickness using special algorithms based on definition of inner and outer retinal border. The purpose of the study was to evaluate the frequency and type of algorithm challenges and their impact on thickness and volume calculation.
129 diabetic patients with clinically significant macular edema (CSME) were enrolled in the study. All eyes were evaluated with OCT before treatment and one month after 3 injections of Ranibizumab. Retinal thickness of the central 1 mm region and retinal volume of the 6 mm region were calculated using 6 lines radial scan pattern (Spectral-domain, Topcon OCT 3D) ignoring decentration errors. All 6 scan lines were evaluated for algorithm errors and when present, retinal thickness and volume was recalculated after manual correction of the artefacts.
A total of 1740 scan lines were evaluated, algorithm errors were found in 24%. The major reason for the errors was: hard exudates (10 %), epiretinal fibrosis (5 %), optical opacities (5 %), serous detachment (3 %) and others (1 %). The mean signal quality was 60 (SD 20), 7 % were below 30 and for these examinations the percentage of algorithm errors of the scans was 55 %. Correction for epiretinal fibrosis caused a 7 % decrease in total macular volume (p=0.007) and 2 % decrease in central retinal thickness (p=0.02). Correction for hard exudates caused a 2 % increase in the central retinal thickness (p=0.002) and 1 % increase in total macular volume (p=0.000002).
The significance of the results for the application of retinal thickness and macular volume as key parameters for the control and treatment of diabetic macular edema will be illustrated and discussed.
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