Semiautomated quantification of β-zone parapapillary atrophy using blue light fundus autofluorescence

To evaluate the reproducibility of measurements of area of β-zone parapapillary atrophy (β-PPA) using blue laser fundus autofluorescence (FAF) and confocal scanning laser ophthalmoscopy reflectance (CSLO) measurements and to assess agreement between the two imaging modalities.

Sixty-five eyes of 45 patients (mean age, 68.2 ± 11.3 years) with established or suspected glaucoma from the Diagnostic Innovations in Glaucoma Study (DIGS) were prospectively included. FAF scans were obtained with the Spectralis HRA+OCT and CSLO reflectance images with the HRTII (both from Heidelberg Engineering, Heidelberg, Germany). Two masked graders independently measured β-PPA area on 3 consecutive scans using the semi-automated BluePeak RegionFinder software (BPRF) and on CSLO reflectance images using the optic disc contour line. Reproducibility of β-PPA area measurements was assessed using intraclass correlation coefficients (ICC).

Intragrader reproducibility was 0.997 (95% CI, 0.996-0.998) and 0.995 (95% CI, 0.992-0.996) for grader 1 and 2, respectively, using FAF-BPRF, and by CSLO, it was 0.991 (95% CI, 0.986-0.994) and 0.988 (95% CI, 0.982-0.992). Intergrader agreement (ICC) was 0.53 (95% CI, 0.331-0.685) for FAF-BPRF and 0.404 (95% CI, 0.149-0.601) for CSLO (comparison between ICC, p = 0.368). Agreement (ICC) between the two devices was worse for grader 1 (0.356; 95% CI, 0.129-0.549) than grader 2 (0.856; 95% CI, 0.774-0.910) (p < 0.001).

Despite excellent intragrader reproducibility for β-PPA measurements with FAF-BPRF and CSLO, intergrader reproducibility is low to moderate. Measurements of β-PPA area obtained with the two instruments are of moderate agreement and, therefore, are not interchangeable.