PENK and type 1 diabetes mellitus: Interactions between the Opioid Growth Factor (OGF) – OGF receptor (OGFr) pathway and the cornea have been reported in diabetic animal models [5-7], but little is known about the effects of type 1 diabetes (T1D) on the limbus in rats or about the role of the OGF-OGFr pathway as a regulatory mechanism that becomes dysregulated in T1D.