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

Abstract

Purpose: To determine whether the Ganzfeld electroretinogram (ERG) photopic negative response (PhNR), an assay of inner retinal activity, is altered in childhood optic pathways glioma (OPG).

Methods: Seventeen pediatric patients with a diagnosis of OPG, established on neuro-ophthalmologic 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 re-tested one to three 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 to normal values, PhNR amplitude was significantly reduced (p < 0.0001) in the OPG group. PhNR peak-time as well as b-wave amplitude and peak-time were similar in both patients and controls. PhNR losses were found in patients with involvement of either anterior or retrochiasmatic optic pathways. Linear regression analysis showed significant positive correlation between RNFL thickness and PhNR amplitude (r²= 0.34, p = 0.01).

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.