Technical advance

Automated analysis of digital fundus autofluorescence images of geographic atrophy in advanced age-related macular degeneration using confocal scanning laser ophthalmoscopy (cSLO)

A Deckert¹ , S Schmitz-Valckenberg² , J Jorzik³ , A Bindewald² , FG Holz² and U Mansmann^1,4

¹Institute of Medical Biometry and Informatics (IMBI), University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany

²Department of Ophthalmology, University Eye Hospital, Abbe-Straß2, 53127 Bonn, Germany

³Department of Ophthalmology, University Eye Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany

⁴Institute of Medical Information, Biometry, and Epidemiology (IBE), University of Munich, Marchioninistrasse 15, 81377 Munich, Germany

author email corresponding author email

BMC Ophthalmology 2005, 5:8doi:10.1186/1471-2415-5-8

Published:	6 April 2005

Abstract

Background

Fundus autofluorescence (AF) imaging using confocal scanning laser ophthalmoscopy (cSLO) provides an accurate delineation of areas of geographic atrophy (GA).

Automated computer-assisted methods for detecting and removing interfering vessels are needed to support the GA quantification process in longitudinal studies and in reading centres.

Methods

A test tool was implemented that uses region-growing techniques to segment GA areas. An algorithm for illuminating shadows can be used to process low-quality images. Agreement between observers and between three different methods was evaluated by two independent readers in a pilot study. Agreement and objectivity were assessed using the Bland-Altman approach.

Results

The new method (C) identifies vascular structures that interfere with the delineation of GA. Results are comparable to those of two commonly used procedures (A, B), with a mean difference between C and A of -0.67 mm² (95% CI [-0.99, -0.36]), between B and A of -0.81 mm², (95% CI [-1.08, -0.53]), and between C and B of 0.15 mm² (95% CI [-0.12, 0.41]). Objectivity of a method is quantified by the mean difference between observers: A 0.30 mm² (95% CI [0.02, 0.57]), B -0.11 mm² (95% CI [-0.28, 0.10]), and C 0.12 mm² (95% CI [0.02, 0.22]).

Conclusion

The novel procedure is comparable with regard to objectivity and inter-reader agreement to established methods of quantifying GA. It considerably speeds up the lengthy measurement process in AF with well defined GA zones.