Abstract

P 242

Intra- and Interobserver variability of atrophy quantification in patients with geographic atrophy secondary to AMD in a reading center setting

Philipp Herrmann, Steffen Schmitz-Valckenberg, Monika Fleckenstein, Arno Göbel, Almut Wittich, Frank G. Holz
Universitäts-Augenklinik Bonn

Objective
Fundus autofluorescence (FAF) images can be used for semi-automated detection of areas of geographic atrophy (GA) due to AMD (Deckert et al. 2005). The aim of this study was to assess the intra- and interobserver reproducibility for the quantification of atrophy in a large multicenter study and in a reading center setting.
Methods
Confocal scanning laser ophthalmoscopy FAF images (Spectralis/Heidelberg Retina Angiograph, Heidelberg Engineering) were evaluated from GA patients that were recruited within the multicenter natural history of geographic atrophy progression (GAP) - study. These were selected in a random fashion. Two independent readers quantified total size of atrophy in 59 GA eyes using semi-automated image analysis software. Furthermore, 28 of these eyes were analyzed a second time by each observer at least one month later in order to assess intraobserver variability. Minimum size for atrophic patches was randomly set at 0.05 mm2. Corresponding infrared reflectance images were viewed side by side to FAF images in order to review delineation of GA areas and their borders. Agreement was assessed by Bland-Altman-strategy.
Results
The average atrophy area from all measured eyes was 7.21 mm2. The mean differences of intraobserver agreements were -0.06 mm2 (95% confidence interval [CI], -0.20 to 0.07) for reader 1 and -0.06 mm2 (95% CI, -0.16 to 0.05) for reader 2. Interobserver agreement showed a mean difference of 0.08 mm2 (95% CI, -0.07 to 0.22). Reasons for disagreement included difficulties in assessing foveal involvement, presence of confluent peripapillary atrophy and small GA satellites.
Conclusions
Standardized semi-automated analysis of atrophy quantification using FAF images represents an accurate method with high reproducibility. Accurate determination of atrophy plays a pivotal role for calculation of atrophy progression over time, particularly with regards to the investigation of new therapeutical interventions in GA patients.

Copyright: 2009 Porstmann Kongresse GmbH. All rights reserved. Impressum, Disclaimer.