Published online Apr 15, 2021. doi: 10.4239/wjd.v12.i4.437
Peer-review started: January 13, 2021
First decision: February 12, 2021
Revised: February 23, 2021
Accepted: March 24, 2021
Article in press: March 24, 2021
Published online: April 15, 2021
Diabetic macular edema (DME) is the most common cause of vision loss in diabetic retinopathy, affecting 1 in 15 patients with diabetes mellitus (DM). The disruption of the inner blood-retina barrier (BRB) has been largely investigated and attributed the primary role in the pathogenesis and progression in DME, but there is increasing evidence regarding the role of outer BRB, separating the RPE from the underlying choriocapillaris, in the occurrence and evolution of DME. The development of novel imaging technologies has led to major improvement in the field of in vivo structural analysis of the macula allowing us to delve deeper into the pathogenesis of DME and expanding our vision regarding this condition. In this review we gathered the results of studies that investigated specific outer BRB optical coherence tomography parameters in patients with DM with the aim to outline the current status of its role in the pathogenesis and progression of DME and identify new research pathways contributing to the advancement of knowledge in the understanding of this condition.
Core Tip: Progress in optical coherence tomography technology allowed the identification of new pathogenic pathways in diabetic macular edema (DME) involving the outer retina and underlying choroid. The presence of fluid in the subretinal space is suggestive for the alteration of the outer blood retinal barrier and responds better to intravitreal triamcinolone as compared to anti- vascular endothelial growth factor. The disruption of external limiting membrane (ELM) is associated with visual impairment being a predictor of poor outcomes following the treatment with triamcinolone. The integrity of ELM and of the inner segment/outer segment line was found to correlate positively with best corrected visual acuity in DME.