In Vivo Retinal Nerve Fiber Layer Thickness Measured by Optical Coherence Tomography Predicts Visual Recovery after Surgery for Parachiasmal Tumors

Abstract

Restoration of visual function after neurosurgery for parachiasmal tumors is variable and unpredictable. The current study was conducted to determine whether in vivo retinal nerve fiber layer (RNFL) thickness measurements predict the visual recovery of such patients. Forty patients undergoing surgical resection of parachiasmal lesions were prospectively assessed before surgery with a neuro-ophthalmic examination, involving standard automated visual field (VF) testing and optical coherence tomography (OCT) measurements of RNFL thickness, which was the prespecified marker for axonal loss. Tests were repeated within 6 weeks after surgery. Thinner preoperative RNFL thickness was associated with worse visual acuity (VA) and VF mean deviation (MD). Patients with normal preoperative RNFL had significant improvement in mean VA after surgery, from 20/40 to 20/25 (P = 0.028), whereas patients with thin RNFL did not improve (20/80 to 20/60, P = 0.177). Eyes with normal RNFL showed improvement in MD (-7.0 dB before surgery, -3.5 dB after surgery, P = 0.0007) unlike eyes with thin RNFLs, which had no significant improvement after surgery (-15.3 dB before and -13.3 dB after surgery, P = 0.191). RNFL thickness increased by 1% after surgery among all eyes (P = 0.04). Eyes with severe VF defects (MD </= -10 dB) but normal preoperative RNFL thickness showed a postoperative improvement in MD of 14.6 dB compared with 1.6 dB (P < 0.0001) in eyes with thin RNFL before surgery, despite no difference in MD before surgery (normal RNFL MD, -22.3 dB; thin RNFL MD, -20.8 dB; P = 0.7). Patients who have objectively measurable RNFL loss at the time of surgery for chiasmal compressive lesions are less likely to have return of VA or VF after surgery.