To quantitatively evaluate the retinal ischemia in different retinal regions of diabetic retinopathy (DR) patients in ultra-widefield fluorescein fundus angiography (UWFA) images with ischemic index (ISI), and to explore its correlation with diabetic macular edema (DME).

A cross-sectional study was conducted.Seventy-nine eyes of 79 patients with DR were enrolled in Renmin Hospital of Wuhan University from September 2017 to October 2020, including 44 males (44 eyes) and 35 females (35 eyes) aged 31 to 73 years old, with an average age of (55.95±8.80) years.UWFA and spectral-domain optical coherence tomography (SD-OCT) were performed in all patients.Patients were divided into DME group (37 eyes) and non-DME group (42 eyes) according to the presence or absence of DME in OCT images.The retina in middle phase UWFA images were divided into posterior, middle peripheral and far peripheral regions by ImageJ software, and ISI in each region was calculated.Central macular thickness (CMT) was automatically calculated using the built-in software of the OCT equipment.The correlation between ISI and CMT was analyzed by Spearman rank correlation analysis.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Renmin Hospital of Wuhan University (No.WDRY2019-K037). Written informed consent was obtained from each patient prior to any medical examination.

The ISI of the total, posterior, middle peripheral and far peripheral retina was 2.460 (0.603, 5.640)%, 2.670 (1.062, 9.574)%, 1.382 (0.245, 4.378)% and 0.000 (0.000, 1.262)%, respectively, with a statistically significant difference among different regions (χ²=65.307, P<0.001). There were statistically significant differences in ISI between the total and far peripheral, the posterior and middle peripheral, the posterior and far peripheral, the middle and far peripheral (all at P<0.01). ISI of the total, posterior and middle peripheral retina in DME group were significantly higher than those in non-DME group (U=424.000, P=0.001; U=403.000, P<0.001, U=493.000, P=0.005), but there was no significant difference in the ISI of the far peripheral region between the two groups (U=609.000, P=0.061). There was no statistically significant correlation between ISI and CMT in the total, posterior, middle peripheral and far peripheral retina in DME group (r_s=-0.134, -0.018, -0.152, -0.163; all at P>0.05).

The retinal non-perfusion area in DR eyes is mainly located in the posterior and middle peripheral retina.The ISI of the posterior and middle peripheral retina in DME eyes is significantly higher than that in eyes without DME.ISI of each retinal region may not be related to the severity of DME.

Diabetic retinopathy; Macular edema; Fluorescein angiography; Tomography, optical coherence