Repeatability and reliability of quantitative fundus autofluorescence imaging in patients with early and intermediate age-related macular degeneration

Purpose Quantification of fundus autofluorescence has only recently become available. We report our findings on the evaluation of the repeatability and reliability of quantitative fundus autofluorescence (qAF) measurements in patients with early and intermediate age-related macular degeneration (AMD), using the first approved and commercially available instrument. Methods A total of 43 eyes of 22 patients (aged between 52 and 84 years) diagnosed with early and intermediate AMD were included. All eyes were imaged at day 1, 3 months and 6 months using a modified scanning laser ophthalmoscope, equipped with an internal fluorescent reference. Mean qAF values were calculated for the fovea and for each concentric ring of the Delori pattern. Repeatability and reliability were calculated using Bland-Altman analysis and intraclass correlation (ICC). Results The mean patient age was 73.5 +/- 7.9 years. Sixteen patients (73%) were female. qAF repeatability of the eight segments in the middle ring of the Delori pattern (qAF(M8)) for between sessions was +/- 8.2%. Agreement at 3- and 6-month follow-up in eyes without retinal changes was +/- 8.3% and +/- 9.8%, respectively. Reliability of qAF(M8) was high for all images acquired [ICC = 0.98 (CI: 0.96-0.99), 0.97 (0.93-0.99) and 0.98 (0.92-0.99)]. Agreement at 3- and 6-month follow-up in eyes with retinal changes was +/- 18.1% and +/- 20.2%, respectively. Intraclass correlation (ICC) was slightly lower in eyes with retinal changes at 0.93 (0.84-0.97) and 0.96 (0.91-0.98), respectively. Conclusions Quantitative autofluorescence shows excellent repeatability and reliability as well as follow-up agreement in patients with early and intermediate AMD without retinal changes. This is relevant when conducting longitudinal studies using qAF.