Long-term effects of trabeculectomy in primary open-angle glaucoma on segmented macular ganglion cell complex alterations

PURPOSE The aim of this study is to compare, using optical coherence tomography (OCT), the changes in the thickness of the macular nerve fiber layer (mNFL), macular ganglion cell layer (mGCL), macular inner plexiform layer (mIPL) and peripapillary global retinal nerve fiber layer (gRNFL) (in a span of 3 years) in surgically treated eyes with primary open-angle glaucoma (POAG). METHODS The medical records of 32 consecutive POAG patients who underwent trabeculectomy with mitomycin-C, between January 2013 and December 2014, were retrospectively reviewed. Pre- and postoperative measurements of IOP and OCT were analyzed 1, 2 and 3 years after the operation. RESULTS Among all patients, no significant changes in the thickness of the mNFL, mGCL or mIPL were found, with a significant reduction observed only in the IOP values and peripapillary gRNFL thickness during the 3-year postoperative period. In a subgroup analysis based on the preoperative peak IOPs (median value:41 mmHg), the thickness of the mNFL, mGCL and mIPL in the 3-year postoperative period increased significantly in the lower preoperative peak IOP group (IOP < 41 mmHg), whereas the macular OCT parameters in the 3-year postoperative period decreased in the higher preoperative peak IOP group. CONCLUSIONS Eyes exhibiting lesser preoperative peak IOP demonstrated greater preservation of the layer-by-layer segmented macular ganglion cell complex thickness as compared to eyes exhibiting greater preoperative peak IOP; also when the IOPs determined for the two groups in the period of follow-up were quite comparable.