Comparison Of Spectral-domain Optical Coherence Tomography And Fundus Autofluorescence In Patients With Geographic Atrophy In A Follow Up Study

Abstract

 

Purpose:

 

In a previous cross sectional study (Sayegh et al., ARVO 2010) comparing fundus auto fluorescence (FAF) versus spectral-domain optical coherence tomography (SD-OCT) choroidal signal enhancement (CSE) and the loss of external limiting membrane(ELM) in SD-OCT B-scans have been shown to be the most solid parameters for geographic atrophy (GA) lesion size detection. The aim of this longitudinal study is to evaluate these parameters in a follow up.

 

Methods:

 

36 eyes of 19 patients with atrophic age-related macular degeneration (AMD) were enrolled based on total GA lesion size ranging from 0.5 to 7 disc areas and best-corrected visual acuity of at least 20/200. A combined cSLO-SD-OCT system (Spectralis HRA-OCT) was used to manually measure disease extent at the level of the outer neurosensory layers and retinal pigment epithelium (RPE) at the site of GA lesions at baseline, month 6 and month 12. Two readers of the VRC graded all obtained volume stacks and the results were correlated to FAF.

 

Results:

 

The mean GA lesion sizes in FAF measured by both graders were 9.81 mm² and 8.52 mm² at baseline. According to the measurements in the follow up the lesion size in FAF increased by 12% at month 6 and 21% at month 12 for grader 1 and respectively by 23% and 34% for grader 2. In SD-OCT the areas of choroidal signal enhancement were 7.47 mm² and 8.03 mm² at baseline and increased by 21% at month 6 and 36% at month 12 respectively by 20% and 32%. The areas of ELM loss in SD-OCT were 7.48 mm² and 6.17 mm² at baseline and increased by 11% at month 6 and 20% at month 12 respectively by 12% and 21%. The area of RPE loss in SD-OCT was constantly smaller (30%-33%) than the hypofluorescent area of GA in FAF during the whole follow up period.

 

Conclusions:

 

This longitudinal study showing smaller areas of RPE loss throughout the study in comparison to hypofluorescent FAF measurements could confirm the reproducibility and accuracy of SD-OCT findings previously demonstrated. Measurements of CSE and ELM loss were not only reliable in the lesion size detection but have also proven to be solid parameters in the follow up. Therefore SD-OCT seems to be an adequate imaging system for monitoring patient with GA secondary to AMD.

 

Keywords: imaging/image analysis: clinical • macula/fovea • retinal pigment epithelium