The Effect of Periodontitis Severity on Diabetic Retinopathy: An Optical Coherence Tomography Study

<b>Background</b>: The aim of this study was to comprehensively investigate the potential degenerative effects of periodontitis severity on retinal and choroidal structures in patients with different types of diabetic retinopathy (DR). <b>Materials and Methods</b>: The study's Clinical Trials Registration Number is NCT07137013. A total of 100 participants (56 females and 44 males), each group consisting of 20 individuals, were allocated into five groups: systemically healthy controls (G1), diabetic patients without DR (G2: DM+ DR-), non-proliferative DR without diabetic macular edema (G3: NPDR DME-), non-proliferative DR with diabetic macular edema (G4: NPDR DME+), and proliferative DR (G5: PDR). Ocular examinations were performed using optical coherence tomography (OCT) and OCT angiography (OCTA). Retinal layer thicknesses, choroid-sclera interface (CSI), ganglion cell layer (GCL), retinal nerve fiber layer (RNFL), and peripapillary CSI were assessed by OCT, whereas superficial and deep retinal vessel densities and the foveal avascular zone (FAZ) were evaluated by OCTA. Clinical periodontal status was assessed using plaque index (PI), gingival index (GI), bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment loss (CAL). <b>Results</b>: In the G3 and G5 groups, the presence of stage III-IV periodontitis was associated with a marked increase in retinal layer thickness. GCL + Inner Plexiform Layer (GCL+) thickness was significantly reduced in individuals with stage III-IV periodontitis in almost all regions of the G5 group, except for the 3 mm nasal and inferior areas. Peripapillary CSI values showed a significant decrease with increasing periodontitis severity. RNFL thickness was significantly reduced in individuals with stage III-IV periodontitis, particularly in the G5 group. OCTA analyses demonstrated significant reductions in superficial and deep retinal vessel densities in several regions in the presence of stage III-IV periodontitis. Moreover, FAZ areas were significantly enlarged in individuals with stage III-IV periodontitis in the G2 and G5 groups. <b>Conclusions</b>: Periodontal inflammation, particularly in advanced periodontitis (stage III-IV), induces degenerative changes in the retinal microvasculature and neural tissues. Increasing periodontitis severity may represent a potential provoking factor in the pathogenesis of DR.