Noninvasive Multimodal Imaging of Diabetic Retinopathy

The abnormalities seen in diabetic retinopathy (DR) can be split into three categories: findings resulting from structural retinal neurodegeneration, findings resulting from leaking microvasculature, and findings resulting from microvascular alterations with ischemia. Noninvasive multimodal imaging, making use of different imaging techniques such as fundus color photography (CFP) and optical coherence tomography (OCT), allows for better characterization of diabetic retinal disease. With the advent of spectral-domain OCT and OCT angiography we may, for the first time, look at the different components of diabetic retinal damage - retinal neurodegeneration, edema, and microvascular changes - in a multimodal approach. The variables that represent microvascular changes (vessel density of superficial retina plexus and deep retinal plexus, foveal avascular zone area and circularity, and microaneurysm turnover), retinal neurodegeneration (thinning of the retinal nerve fiber layer and ganglion cell layer + inner plexiform layers), and retinal edema (increased thickness of the inner nuclear and outer plexiform layers of the retina) show a wide range of values between different eyes in each nonproliferative DR ETDRS (Early Treatment Diabetic Retinopathy Study) level, demonstrating that there are very different degrees of microvascular damage, neurodegenerative changes, and edema in different eyes in the same retinopathy grade. This conclusion supports the concept of three major phenotypes of retinal disease in type 2 diabetes. This noninvasive approach allows for repeated examinations in longitudinal studies, helping in finding specific progression patterns to personalize treatment and follow-up.