Researchers have found in a new study that advanced periodontal inflammation (stage III–IV) may cause degenerative changes in retinal microvasculature and neural tissues. The increasing severity of periodontitis could act as a potential contributing factor in the development of diabetic retinopathy (DR). The study was published in the Diagnostics journal by Hatice T. and colleagues.Diabetic retinopathy is one of the most prevalent microvascular complications of diabetes mellitus and continues to be a major cause of blindness worldwide. The condition is characterized by progressive alterations to the retinal blood vessels, resulting in structural and functional changes to the retina. Systemic inflammation is thought to play a major role in the pathogenesis of diabetic retinal disease. Periodontitis is a chronic inflammatory disease that affects the supporting structures of the teeth. There is an increasing association between periodontitis and systemic inflammatory conditions, such as diabetes and cardiovascular disease.This trial was performed as a clinical observational study and is registered with Clinical Trials Registration Number NCT07137013. A total of 100 participants, including 56 females and 44 males, were selected and equally divided into five groups of 20 participants each, depending on their systemic and ocular health conditions.The five groups of participants were systemically healthy controls (Group 1), diabetic patients without diabetic retinopathy (Group 2: DM with no DR), patients with non-proliferative diabetic retinopathy without diabetic macular edema (Group 3: NPDR without DME), patients with non-proliferative diabetic retinopathy with diabetic macular edema (Group 4: NPDR with DME), and patients with proliferative diabetic retinopathy (Group 5: PDR).Key findings:This clinical trial was conducted on 100 subjects (56 females and 44 males) divided into five groups of 20 people each, including healthy controls, patients with diabetes without retinopathy, patients with non-proliferative diabetic retinopathy with and without macular edema, and patients with proliferative diabetic retinopathy. Stage III-IV periodontitis was linked to the increased thickness of the retinal layer in Groups 3 and 5, indicating retinal structural changes. The thickness of the ganglion cell layer and inner plexiform layer was significantly decreased in most retinal areas in patients with stage III-IV periodontitis in the proliferative diabetic retinopathy group, except for the 3mm nasal and inferior areas.The thickness of the retinal nerve fiber layer was also significantly decreased, especially in the proliferative diabetic retinopathy group. The peripapillary choroid-sclera interface was decreased with the severity of periodontitis, indicating choroidal structural degeneration. The results of the OCT angiography analysis showed a significant decrease in the superficial and deep retinal vessel density, and the foveal avascular zone area was significantly enlarged in patients with severe periodontitis in the diabetic group without retinopathy and the proliferative diabetic retinopathy group.Severe periodontal inflammation was linked to degenerative changes in the retinal neural tissues and microvasculature of patients with diabetic retinopathy. The increasing severity of periodontitis could be a potential provoking factor in the development and progression of diabetic retinal disease.Reference:Turkogullari, H., Aydogan, G. N., Yorgancilar, N., Kose, O., & Findik, H. (2026). The Effect of Periodontitis Severity on Diabetic Retinopathy: An Optical Coherence Tomography Study. Diagnostics, 16(5), 654. https://doi.org/10.3390/diagnostics16050654