Figure 5. Retinal nerve fiber layer thickness values (μ) on optical coherence tomography in different diabetic retinopathy stages. *Control versus NoDR, NPDR, and PDR: significant differences, with the control having higher RNFL thickness. NoDR versus NPDR and PDR: no significant differences. NPDR versus PDR: no significant differences. OCT - optical coherence tomography, RNFL - retinal nerve fiber layer, NoDR - no diabetic retinopathy, NPDR - non-proliferative diabetic retinopathy, PDR - proliferative diabetic retinopathy.