Purpose To evaluate longitudinal quantitative ischaemic and vasculature parameters, including ischaemic index, vessel area, length and geodesic distance in sickle cell retinopathy (SCR) on ultra-widefield fluorescein angiography (UWFA).
Methods Optimal UWFA images from two longitudinal timepoints of 74 eyes from 45 patients with SCR were aligned and a common region of interest was determined. A deep-learning augmented ischaemia and vascular segmentation platform was used for feature extraction. Geodesic distance maps demonstrating the shortest distance within the vascular masks from the centre of the optic disc were created. Ischaemic index, vessel area, vessel length and geodesic distance were measured. Paired t-test and linear mixed effect model analysis were performed.
Results Overall, 25 (44 eyes) patients with HbSS, 14 (19 eyes) with HbSC, 6 (11 eyes) with HbSthal and other genotypes were included. Mean age was 40.1±11.0 years. Mean time interval between two UWFA studies was 23.0±15.1 months (range: 3–71.3). Mean panretinal ischaemic index increased from 10.0±7.2% to 10.9±7.3% (p<0.005). Mean rate of change in ischaemic index was 0.5±0.7% per year. Mean vessel area (p=0.020) and geodesic distance (p=0.048) decreased significantly. Multivariate analysis demonstrated baseline ischaemic index and Goldberg stage are correlated with progression.
Conclusion Longitudinal ischaemic index and retinal vascular parameter measurements demonstrate statistically significant progression in SCR. The clinical significance of these relatively small magnitude changes remains unclear but may provide insights into the progression of retinal ischaemia in SCR.
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Contributors DDS was involved in image analysis, study organisation, supervision and manuscript drafting; AWS and JPE were involved conception, study design, supervision, resource/funding support and manuscript review; AM and CM were involved in data acquisition, image analysis and manuscript review; PS, MOL, and AN were involved in data acquisition, study execution and manuscript review; JR was involved in supervision, resource support and manuscript review.
Funding This study was funded by NIH/NEI K23-EY022947-01A1 (JPE) and Betty J. Powers Retina Research Fellowship (DDS).
Competing interests DDS, AM, CM, PS, MOL, AN, JR: None to disclose. AWS: Consulting: Allergan, Novartis. JPE: Research Support: Aerpio, Alcon, Thrombogenics/Oxurion, Regeneron, Genentech, Novartis, Allergan. Consulting: Aerpio, Alcon, Allegro, Allergan, Genentech/Roche, Novartis, Thrombogenics/Oxurion, Leica, Zeiss, Regeneron, Santen. Patent: Leica.
Ethics approval This retrospective image analysis study was approved by the Institutional Review Board of Johns Hopkins University. Patient consent is not required for the publication.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon request.
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