Assessment the neurodegenaration process of post-geniculate optic pathway in thalamic tumors using optical coherence tomography: Post-geniculate optic pathway in thalamic tumors.

[PURPOSE] To investigate the effect of thalamic tumors related to post-geniculate optic pathway and those of microsurgical removal on neurodegeneration process of visual pathway using OCT.

[METHODS] This cross-sectional study included 30 eyes of 15 patients with thalamic tumors and data compiled from 45 eyes of 45 healthy participants. The analysis of variables was divided into ipsilateral and contralateral eye depends on the laterality of brain tumors. The data gained at baseline, postoperative 3rd and postoperative 6th month period was analyzed in One-Way Repeated Measures ANOVA.

[RESULTS] The mean superior quadrant retinal nerve fiber layer (RNFL) thickness of ipsilateral eye was significantly thicker (p = 0.02), while inferior hemifield ganglion cell-inner plexiform layer (GC-IPL) thickness of contralateral eye was significantly higher compared to control groups (p = 0.02). Significant negative correlations were found between the mean preop. mean deviation (MD) and tumor volume and time interval between initial diagnosis and surgery (r = - 0.730, p = 0.002 and r = - 0.680, p = 0.005, respectively) in the ipsilateral eye. In repeated measure analysis, there was no unfavourable effect of thalamic microsurgery on peripapillary average RNFL thickness on both ipsilateral and contralateral eyes (Ipsilateral eye; f (1.5,21.7) 0.76 p = 0.51 and contralateral eye; f (1.4,20.4) 0.42 p = 0.59).

[CONCLUSION] This study suggests that thalamic tumors affecting post-geniculate optic pathway may lead to significant increase in RNFL and GC-IPL thicknesses and changes in VF parameters. Timely intervention in thalamic tumors may prevent irreversible loss of retinal axons secondary to neurodegeneration process.