Objectives: The primary goal of this study was to determine the relationship between diabetic peripheral neuropathy and retinal nerve fiber layer (RNFL) thickness among elderly Filipinos with type 2 diabetes mellitus.
Methodology: This was a cross-sectional study involving 106 subjects aged 60 years or older with type 2 diabetes mellitus recruited from the General Medicine and Diabetes Clinics of a tertiary government hospital. The diagnosis of peripheral neuropathy was made by performing a 10-gram monofilament test. Peripapillary retinal nerve fiber layer thickness was measured using the optic disc cube 200 x 200 protocol of the Cirrus® HD-OCT. T-test was used to compare RNFL thickness in those with and without peripheral neuropathy. The effects of age, sex, duration of diabetes, presence or absence of peripheral neuropathy, and retinopathy status on global and quadrantal RNFL thickness was assessed using multivariate analysis.
Results: Compared to subjects without peripheral neuropathy, significant thinning of the superior (P=0.011), inferior (P=0.004), and global (P=0.008) RNFL thickness were observed in subjects with peripheral neuropathy. There were no significant differences in RNFL thickness in the temporal (P=0.211) and nasal (P=0.263) quadrants between the 2 groups. Multivariate regression analysis revealed that presence of peripheral neuropathy has a significant effect on their superior (P=0.036), inferior (P=0.010), and global (P=0.024) RNFL thickness. Other factors such as age, sex, duration of diabetes, and retinopathy had no effect on global and quadrantal RNFL thickness.
Conclusion: RNFL thinning in the superior, inferior, and global indices on optical coherence tomography has a significant correlation with diabetic peripheral neuropathy.
Keywords: Diabetic peripheral neuropathy, optical coherence tomography, retinal nerve fiber layer thinning, diabetes mellitus, retinopathy