Assessment of macular anatomical and microvascular structures in patients with proliferative diabetic retinopathy before and after panretinal photocoagulation

Objective: To investigate the anatomical and microvascular changes in the macula following panretinal photocoagulation (PRP) treatment in eyes diagnosed with proliferative diabetic retinopathy (PDR). Materials and Methods: This study included 39 eyes of 26 patients diagnosed with PDR requiring laser treatment who presented to the outpatient clinic and Retina Unit of the Department of Ophthalmology at Akdeniz University Faculty of Medicine. None of the included patients had previously undergone any laser treatment. Best corrected visual acuity (BCVA), comprehensive ophthalmologic examinations, optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) were performed before PRP treatment and at months 1, 3, and 6 posttreatment. OCT parameters included central and parafoveal retinal thickness, ganglion cell layer thickness, and submacular choroidal thickness measurements. In OCTA, the FAZ (foveal avascular zone) areas in both the deep and superficial capillary plexuses were measured, along with vascular density (%) in the central and four parafoveal quadrants of both plexuses. FAZ images were analyzed using the ImageJ software and circularity index, perimeter value and roundness value were calculated. Additionally, the duration of diabetes mellitus (DM), the type of DM treatment received, and pre-PRP HbA1c levels were recorded. Results: The mean age of the patients was 57.35±12.06 years, and the mean pre-treatment HbA1c level was 8.5±1.7. The mean pretreatment central choroidal thickness was 272.85±62.28 µm, which decreased to 265.74±60.66 µm at month 1, 261.23±54.42 µm at month 3, and 257.03±56.22 µm at month 6 post-treatment. This reduction was statistically significant (p < 0.001). A significant decrease in FAZ area was observed at months 3 (p < 0.001) and 6 (p < 0.001) post-treatment compared to baseline. However, no significant differences were detected in FAZ circularity index (CI) and perimeter values. No significant change was observed in BCVA across follow-up visits compared to baseline. Conclusion: A significant reduction in central choroidal thickness was observed following PRP treatment, supporting the impact of PRP on choroidal circulation. Additionally, a significant narrowing of the FAZ area was detected at months 3 and 6, indicating the potential role of PRP in controlling macular ischemia. Key words; Diabetic retinopathy, panretinal photocoagulation, optical coherence tomography angiography, foveal avascular zone