The Time Course of Visual Field Recovery and Changes of Retinal Ganglion Cells after Optic Chiasmal Decompression

Abstract

To investigate the time course of visual field recovery and changes of retinal ganglion cells (RGCs) after chiasmal decompression using standard automated perimetry (SAP), optical coherence tomography (OCT), and photopic negative response (PhNR). Nineteen patients undergoing chiasmal decompression surgery were prospectively assessed before and 1 and 3 months after surgery. The same examinations were conducted in nine patients at 6 months after surgery. Mean deviation and temporal visual field sensitivity (1/Lambert) of SAP, retinal nerve fiber layer (RNFL) thickness, and ganglion cell complex (GCC) area measured by OCT and PhNR/b-wave ratio were analyzed. Preoperative measurements were compared with those of 20 eyes of normal controls. Postoperative measurements were compared with preoperative data. The relationships among SAP, OCT, and PhNR measurements throughout the observation periods were evaluated by linear and logarithmic regressions. Before surgery, all parameters in patients were significantly worse than those in normal controls. After surgery, the visual field was significantly improved, but RNFL thickness and GCC area were significantly reduced for 3 months. The PhNR/b-wave ratio was also reduced, but not significantly. Six months after surgery, average RNFL thickness, GCC area, and PhNR/b-wave ratio showed significant improvements by 2.82%, 2.66%, and 8.72%, respectively, than those at 3 months. Visual fields were significantly correlated with RNFL thickness, GCC area, and PhNR/b-wave ratio. Visual field recovery and changes of RGCs after chiasmal decompression have similar aspects and are significantly correlated. However, prolonged retrograde degeneration progressed for some period, even after surgical decompression and visual field recovery preceded demonstrable retinal regeneration.