Original StudyOPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY ASSESSMENT OF THE DIABETIC MACULA A Comparison Study Among Different AlgorithmsBorrelli, Enrico MD, FEBO*; Sacconi, Riccardo MD, FEBO*; Parravano, Mariacristina MD†; Costanzo, Eliana MD†; Querques, Lea MD*; Battista, Marco MD*; Grosso, Domenico MD*; Giorno, Paola MD†; Bandello, Francesco MD, FEBO*; Querques, Giuseppe MD, PhD*Author Information *Department of Ophthalmology, University Vita-Salute, IRCCS Ospedale San Raffaele, Milan, Italy; and †IRCCS—Fondazione Bietti, Rome, Italy. Reprint requests: Giuseppe Querques, MD, PhD, Department of Ophthalmology, University Vita-Salute, IRCCS Ospedale San Raffaele, Via Olgettina 60, Milan 20132, Italy; e-mail: [email protected] F. Bandello is a consultant for Alcon (Fort Worth, Texas), Alimera Sciences (Alpharetta, Georgia), Allergan Inc (Irvine, California), Farmila-Thea (Clermont-Ferrand, France), Bayer Shering-Pharma (Berlin, Germany), Bausch and Lomb (Rochester, New York), Genentech (San Francisco, California), Hoffmann-La-Roche (Basel, Switzerland), Novagali Pharma (Évry, France), Novartis (Basel, Switzerland), Sanofi-Aventis (Paris, France), Thrombogenics (Heverlee, Belgium), and Zeiss (Dublin). G. Querques is a consultant for Alimera Sciences (Alpharetta, Georgia), Allergan Inc (Irvine, California), Amgen (Thousand Oaks), Bayer Shering-Pharma (Berlin, Germany), Heidelberg (Germany), KBH (Chengdu; China), LEH Pharma (London, UK), Lumithera (Poulsbo), Novartis (Basel, Switzerland), Sandoz (Berlin, Germany), Sifi (Catania, Italy), Sooft-Fidea (Abano, Italy), and Zeiss (Dublin). M. Parravano is a consultant for Allergan Inc (Irvine, California), Bayer Shering-Pharma (Berlin, Germany), and Novartis (Basel, Switzerland). The remaining authors have no financial/conflicting interests to disclose. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.retinajournal.com). The PLEX Elite 9000 has been made available through the Advanced Retina Imaging Network for which Giuseppe Querques is a steering Committee Member. The research for this article for the contribution of the IRCCS-Fondazione Bietti was financially supported by Italian Ministry of Health and Fondazione Roma. Retina: September 2021 - Volume 41 - Issue 9 - p 1799-1808 doi: 10.1097/IAE.0000000000003145 Buy SDC Metrics AbstractIn Brief Purpose: To assess the impact of histogram adjustments and binarization thresholding selection on quantitative measurements of diabetic macular ischemia using optical coherence tomography angiography (OCTA). Methods: Patients with diabetic retinopathy (DR) who had swept-source OCTA imaging obtained were enrolled. An additional group of 15 healthy control subjects was included for comparison. Previously used brightness/contrast changes and binarization thresholds were applied to original OCTA images to obtain and compare different binarized images. Qualitative and quantitative comparisons were performed. Results: Thirty patients with DR (30 eyes) were included in the analysis. Fifteen eyes displayed the presence of diabetic macular edema. Qualitative grading revealed that binarized images obtained using a global threshold had better quality compared with local or multistep thresholds. The “median” filter was most frequently graded as the histogram adjustment resulting in binarized images with best quality. In the quantitative analysis, local thresholds tended to generate higher values of measured metrics. Differences in OCTA metrics between global and local thresholds were associated with presence of diabetic macular edema and signal strength index value. In the comparison between healthy and DR eyes, differences in OCTA metrics were significantly affected by binarization threshold selection. Conclusion: Quantitative OCTA parameters may be significantly influenced by strategies to quantify macular perfusion. Image quality and presence of macular edema can significantly impact OCTA-derived quantitative vascular measurements and differences between global and local binarization thresholds. These findings highlight the importance of consistent strategies to reliably generate quantitative OCTA metrics in patients with DR. Quantitative optical coherence tomography angiography parameters may be significantly influenced by strategies to quantify macular perfusion. Image quality and presence of macular edema are associated with differences in optical coherence tomography angiography–derived quantitative vascular measurements among different algorithms.