Correlation between retinal nerve fibre layer thickness, intraocular pressure, and BMI in diabetic patients without diabetic retinopathy

Background Alterations in the retinal nerve fibre layer (RNFL) thickness signify early retinal damage, whereas increased intraocular pressure (IOP) can cause irreversible damage to the optic nerve. Diabetes as well as obesity are considered risk factors which affect both IOP and RNFL thickness. Aim To evaluate IOP and investigate the change in RNFL in diabetics without retinopathy (NDR) and correlate that with the BMI. Patients and method A case-control study at ophthalmology department, Menoufia University, was conducted on 60 participants of both sex who met our inclusion criteria and we divided them into; 30 eyes nondiabetic (control group) and 30 eyes diabetic without DR (NDR). A detailed medical and ophthalmic history, visual acuity assessment (Uncorrected and best corrected), IOP measurement, anterior segment and fundus examination, and RNFL thickness using spectral domain optical coherence tomography (OCT) were assessed. Results IOP was significantly higher in NDR (P < 0.001). Average and all quadrents of RNFL thickness were statistically significantly lower among NDR (P < 0.001, P < 0.001, P = 0.031, P < 0.001, P = 0.033), respectively. RNFL thickness negatively correlated with BMI of NDR and control group (r = -0.594, r = -0.776), respectively, IOP was positively correlated with BMI of NDR and control group (r = 0.735, r = 0.757), respectively. Conclusion In diabetic patients who do not yet have retinopathy RNFL thinning could be the first alteration seen in the retina and BMI could be an independent contributor for these changes through our study, also associated with glycosylated hemoglobin and diabetic duration. Moreover, diabetics particularly those with higher BMI were associated with increased levels of IOP.