This cross-sectional study assessed corneal thickness in association with diabetic peripheral neuropathy (DPN) severity. The study also tried to identify the layer of the cornea most affected by DPN status. Performed at the University of Michigan the study included three groups of patients, those with diabetes and mild DPN, with diabetes and severe DPN and healthy controls. Inclusion criteria were age 18 years and older, presence of diabetes defined by the American Diabetes Association for the group with diabetes and having at least some evidence of DPN for the group with diabetes. Patients with neurodegenerative conditions, other systemic neuropathy and previous corneal disease or eye surgery were excluded. DPN status was assessed by clinical examination, nerve conduction studies and quantitative sensory testing. central corneal thickness (CCT) was measured by ultrasound pachymetry, and the thickness of corneal layers was assessed by confocal microscopy. There were 34 participants of which nine were controls, 16 with mild DPN and nine with severe DPN. The data showed an 11% increase in corneal thickness among severe DPN compared with controls, a 5.6% increase in corneal thickness among mild DPN compared with controls, and a 4.9% increase in CCT among severe DPN cases compared with mild cases. Confocal microscopy showed a significant increase in stromal thickness in mild and severe DPN groups compared with controls. Endothelial and epithelial thicknesses and endothelial cell count did not differ significantly between the three study groups. Based on the confocal microscopy results, this increase in CCT can be attributed to an increase in corneal stromal thickness with increasing DPN severity. In contrast to previous studies that reported an increase in IOP among patients with diabetes, IOP results in this study did not differ among the three groups. This discrepancy could be due to lower power associated with the sample size in this study. Two postulated mechanisms for the increase in CCT are collagen cross-linking and stromal hydration.

Central corneal thickness increase due to stromal thickening with diabetic peripheral neuropathy severity.
Kumar N, Pop-Busui R, Musch DC, et al.
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Bushra Thajudeen

Singleton Hospital, Swansea, UK.

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