Emerging Issues for Optical Coherence Tomography.

Almost 25 years after its introduction, optical coherence tomography (OCT) is still a crucial test in the evaluation of patients affected by diabetic retinopathy. In this chapter, the authors provide an extensive overview of the posterior segment pathological changes induced by diabetes, characterized using OCT. OCT plays a key role in diabetic macular edema (DME) as it assesses related retinal changes both in a qualitative (i.e., DME pattern, presence and aspects of cysts, fluid localization, integrity, and reflectivity of retinal layers) and quantitative (i.e., macula volume, central and sectorial retinal thickness) way, and it is therefore essential for diagnosis, characterization, and follow-up of DME. Diabetic macular ischemia is associated with retinal structural changes which can be investigated using OCT, although its diagnosis relies mostly on fluorescein angiography. Beyond DME and macular ischemia, OCT permits the individuation of many other lesions occurring in the setting of both non-proliferative (i.e., hyperreflective spots, micropseudocysts, hard exudates, microaneurysm, cotton-wool spots) and proliferative (i.e., neovascularization, vitreoschisis, tractional retinal detachment, hemorrhage) retinopathies. OCT provides precious information on several structures, including vitreo-retinal interface, retinal nerve fiber layers, ganglion cell complex, and choroid.