Purpose: To investigate longitudinal changes in retinal nerve fiber layer (RNFL) thickness after panretinal photocoagulation (PRP) in diabetic retinopathy patients.
Methods: This prospective study examined 31 eyes in 25 patients undergoing PRP, who were diagnosed with severe nonproliferative diabetic retinopathy or non-high-risk proliferative diabetic retinopathy. Optical coherence tomography was conducted before PRP and at 3, 6, 12, and 24 months after PRP to investigate changes in peripapillary RNFL thickness.
Results: Superior, nasal, inferior, temporal, and mean peripapillary RNFL thickness increased until 6 months after PRP and then decreased. Superior RNFL thickness increased significantly at 3 and 6 months and decreased significantly at 24 months compared with the baseline RNFL thickness. Nasal RNFL thickness declined significantly at 24 months compared with the baseline RNFL thickness without any significant increase in thickness during the follow-up period. Inferior RNFL thickness increased significantly at 6 months and decreased significantly at 24 months compared with its baseline RNFL thickness. Temporal thickness increased significantly at 3, 6, 12, and 24 months compared with the baseline RNFL thickness. Mean RNFL thickness increased significantly at 6 months and decreased significantly at 24 months. Central subfield thickness increased significantly at 3, 6, 12, and 24 months compared with its baseline thickness.
Conclusion: Peripapillary RNFL thickness increased at 6 months after PRP and then decreased at 24 months after PRP compared with baseline peripapillary RNFL thickness in diabetic retinopathy patients. This finding suggests that in addition to diabetes itself, diabetic retinopathy, and associated glaucoma, PRP may be a cause of RNFL thickness loss in patients with diabetes.