تقارن نانپرفیوژن محیطی شبکیه در رتینوپاتی دیابتی با شاخص های ایسکمیک Symmetry of peripheral retinal nonperfusion in diabetic retinopathy by ischemic index

Introduction Diabetes mellitus affects approximately 422 million individuals worldwide and the global prevalence has nearly doubled since 1980.1 Diabetic retinopathy (DR) is the leading cause of blindness among working-aged adults and affects about 92 million people globally.2 Owing to the systemic nature of the disease, DR affects eyes bilaterally and usually develops in a relatively symmetric pattern over time, although few studies have looked at this directly. Laron et al. investigated the spatial correspondence of abnormal multifocal electroretinogram responses in adolescents with type 1 diabetes and no retinopathy. Their results showed high agreement (68—94%) of inter-ocular correspondence of locations of abnormal multifocal electroretinogram implicit times, suggesting a symmetrical disease process even before the presence of clinically visible DR.3 Iino et al. prospectively followed a cohort of diabetic patients with and without symmetrical DR for the development of brain infarction. While not the main outcome of their study, they reported that only 12 of 142 (8.4%) patients had asymmetric retinopathy.4 Other studies have reported asymmetric DR in 5—10% of patients with proliferative disease.5 There has been increasing interest in peripheral retinal involvement in DR. Predominantly peripheral lesions have been associated with an increased risk of progression of both non-proliferative diabetic retinopathy and of conversion to proliferative disease. Predominantly peripheral lesions are identified by more than 50% of the lesion being located outside the seven standard fields of the Early Treatment Diabetic Retinopathy Study (ETDRS).6 These peripheral lesions are hypothesized to come from underlying capillary non-perfusion.7 Recent technological advances have greatly improved the evaluation of capillary function in the peripheral retina. Compared to standard fluorescein angiography which covers 15% of the retinal surface with the 45 degree images, ultra-widefield fluorescein angiography (UWFA) provides extended peripheral retinal views and covers 82% of the retina with the 200 degree field of view, captured in a single frame.8 The purpose of this study was to evaluate the symmetry of the amount of peripheral retinal nonperfusion in patients with diabetic retinopathy. In this article, we define symmetry as the likeness of the total value of peripheral non-perfusion as measured by ischemic index (ISI) in the right eye compared to the left eye. To our knowledge, no prior studies have reported on this.