Interconnections between diabetic corneal neuropathy and diabetic retinopathy: diagnostic and therapeutic implications

Diabetic corneal neuropathy and diabetic retinopathy are ocular complications occurring in the context of diabetes mellitus. Diabetic corneal neuropathy refers to the progressive damage of corneal nerves. Diabetic retinopathy has traditionally been considered as damage to the retinal microvasculature. However, growing evidence suggests that diabetic retinopathy is a complex neurovascular disorder resulting from dysfunction of the neurovascular unit, which includes both the retinal vascular structures and neural tissues. Diabetic retinopathy is one of the leading causes of blindness and is frequently screened for as part of diabetic ocular screening. However, diabetic corneal neuropathy is commonly overlooked and underdiagnosed, leading to severe ocular surface impairment. Several studies have found that these two conditions tend to occur together, and they share similarities in their pathogenesis pathways, being triggered by a status of chronic hyperglycemia. This review aims to discuss the interconnection between diabetic corneal neuropathy and diabetic retinopathy, whether diabetic corneal neuropathy precedes diabetic retinopathy, as well as the relation between the stage of diabetic retinopathy and the severity of corneal neuropathy. We also endeavor to explore the relevance of a corneal screening in diabetic eyes and the possibility of using corneal nerve measurements to monitor the progression of diabetic retinopathy.