Functional loss of the inner retina in childhood optic gliomas detected by photopic negative response

PURPOSE. To determine whether the Ganzfeld ERG photopic negative response (PhNR), an assay of inner retinal activity, is altered in childhood optic glioma (OPG). METHODS. Seventeen pediatric patients with a diagnosis of OPG, established on neuroophthalmologic and brain/orbit magnetic resonance imaging (MRI) criteria, were enrolled. The examination protocol included determination of visual acuity (VA), fundus examination, retinal nerve fiber layer (RNFL) measurement with spectral-domain optical coherence tomography (SD-OCT) and photopic ERG. Fifteen normal children served as control group. Ten of the 17 OPG patients were retested 1 to 3 months after the first examination. Photopic ERGs were recorded after 10 minutes of light adaptation in response to a Ganzfeld flash presented on a steady light-adapting background. Amplitude and peak-time of b-wave and PhNR were measured. RESULTS. Compared with normal values, PhNR amplitude was significantly reduced (P < 0.0001) in the OPG group. Peak-time of PhNR as well as b-wave amplitude and peak-time were similar in both patients and controls. Losses of PhNR were found in patients with involvement of either anterior or retro-chiasmatic optic pathways. Linear regression analysis showed significant positive correlation between RNFL thickness and PhNR amplitude (r2 = 0.34, P = 0.008). Mean percentage test-retest difference for PhNR amplitude and peak-time was 12% and 6%, respectively. CONCLUSIONS. These findings indicate that flash ERG PhNR can detect a loss of inner retinal function in childhood OPGs supporting the use of this technique, as an adjunct to standard psychophysical and electrophysiological tests, to monitor visual function in OPG.