Long-term changes in the peripapillary RNFL and macular GCIPL thicknesses after panretinal photocoagulation in diabetic retinopathy patients

Purpose: To investigate longitudinal changes in the thicknesses of the peripapillary retinal nerve fiber layer (pRNFL) and the macular ganglion cell-inner plexiform layer (mGCIPL) in patients with diabetic retinopathy 3 years after panretinal photocoagulation (PRP). Methods: We retrospectively reviewed the medical records of 60 eyes of 35 patients who were diagnosed with diabetic retinopathy and treated with PRP. The pRNFL and mGCIPL thicknesses were measured by optical coherence tomography at baseline, and then at 1, 3, 6, 9, 12, 24, and 36 months after PRP. Results: The pRNFL and mGCIPL thicknesses (average and all sections) at 1 year after PRP increased significantly from baseline (p < 0.05, respectively). The average pRNFL and mGCIPL thicknesses showed a tendency to decrease continuously from 2 years after PRP (p < 0.05, respectively). There was no statistically significant difference in the average thicknesses of the pRNFL and the mGCIPL between pre-PRP (92.27 ± 7.76 µm, and 85.00 ± 4.80 µm, respectively) and 3 years after PRP (93.93 ± 7.49 µm, and 81.87 ± 14.00 µm, respectively) (p = 0.121, and p = 0.622, respectively). Conclusions: Although the pRNFL and the mGCIPL thicknesses increased at 1 year after PRP, there was no statistical difference in the average thicknesses of the pRNFL and the mGCIPL between pre-PRP and 3 years after PRP. These results should be considered with respect to the diagnosis and progression of glaucoma in patients with diabetic retinopathy who undergo PRP.