Comparison of Clarus, Optos, and Heidelberg Systems for Geographic Atrophy Area Measurements

To compare geographic atrophy (GA) area measurements across 3 modern fundus autofluorescence (FAF) imaging platforms: Heidelberg Spectralis, Optos California, and Zeiss Clarus 700.

A prospective, single-center, cross-sectional comparative imaging study.

Sixty-one eyes from 39 participants aged ≥50 years with GA secondary to age-related macular degeneration.

Participants were imaged sequentially on the same day with all 3 devices: Optos California FAF (532 nm green excitation, 200° ultra-widefield), Zeiss Clarus 700 FAF (blue 435-500 nm and green 500-585 nm channels, 133° widefield), and Heidelberg Spectralis FAF (488 nm blue excitation, 30° field). Geographic atrophy was segmented with manual planimetry for all modalities; Heidelberg images were also segmented semiautomatically with RegionFinder. RegionFinder area values served as the reference standard for comparisons.

Mean GA area by imaging system and agreement with RegionFinder.

Agreement with RegionFinder was high across imaging systems (intraclass correlation coefficients: 0.96-0.99), but systematic differences were noted in GA area measurements. Geographic atrophy measured larger on average with Clarus Green and Heidelberg manual planimetry (0.49 mm² [95% confidence interval [CI], 0.23 to 0.75] and 0.34 mm² [95% CI, 0.22 to 0.45], respectively), while Optos California measured smaller areas (-0.47 mm² [95% CI, -0.81 to -0.13]).

Geographic atrophy area measurements are reproducible within each FAF imaging system but systematically differ between platforms and wavelengths. Repeated use with the same device recommended for clinical trials.

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