Optical coherence tomography angiography in the evaluation of geographic atrophy area extension

PURPOSE. To investigate the application of optical coherence tomography angiography (OCT-A) in evaluation of geographic atrophy (GA) secondary to age-related macular degeneration (AMD). METHODS. Patients with GA were prospectively enrolled and studied with blue fundus autofluorescence (FAF), en face structural OCT, and OCT-A. OCT-A images were acquired using a slab of whole choroid, whereas en face structural OCT images were obtained at the ellipsoid zone (EZ), at the choroidal (CH) level, and at the scleral (SC) level. Three readers independently measured the GA extension areas and evaluated the foveal sparing in each examination. Intraobserver/interobserver agreements and agreement between each couple of imaging techniques were assessed. RESULTS. A total of 47 eyes (26 patients, mean age 76 ± 7 years) with GA (mean area using FAF: 8.77 ± 5.00 mm2) were included. Intraobserver and interobserver agreement was excellent for all imaging techniques (intraclass correlation coefficient [ICC] > 0.985), even if en face EZ structural OCT revealed the poorest quality agreement limits. Considering the analysis between each couple of imaging techniques, ICC was excellent between OCT-A compared with FAF (ICC: 0.995), followed by en face structural OCT at CH level (ICC: 0.992), at SC level (ICC: 0.986), and at EZ level (ICC: 0.973). No differences were detected between multifocal and monofocal GA lesions. Considering the evaluation of foveal involvement, lower agreements were disclosed between FAF and all other imaging techniques. CONCLUSIONS. OCT-A is a reliable technique for easily visualizing and quantifying GA with the advantages, compared to current imaging techniques, of offering together both structural and blood flow information regarding retinal and choroidal layers and excluding choroidal neovascularization.