Degradation of Swept-Parameter VEP Responses by Neutral Density Filters in Amblyopic and Normal Subjects

Abstract

Neutral density filtration causes preferential degradation of both threshold and suprathreshold sVEP responses in normal control eyes and fellow eyes of amblyopes, compared to amblyopic eyes. The degradation is stimulus specific and dependent upon whether threshold or suprathreshold responses are measured. Grating responses are more likely to identify suprathreshold abnormalities, while vernier stimuli are more likely to detect threshold abnormalities. These findings may be used to optimize the stimulus parameters and design of future studies utilizing evoked potential techniques in amblyopic subjects.

Rapid Objective Assessment of Contrast Sensitivity and Visual Acuity With Sweep Visual Evoked Potentials and an Extended Electrode Array

“…Moreover, measuring a greater suprathreshold amplitude may help diagnose amblyopia, as suprathreshold amplitudes are differently impacted by a neutral density filter with a grating stimuli, depending on whether the participant has normal or amblyopic eyes. 32 Our testing of visual acuity has shown a lateralization over the right occipital region for low spatial frequencies. This is in line with findings by Merigan and Maunsell 36 that in the macaque monkey brain these spatial frequencies follow a specific pathway posterior to the thalamus: they are quickly processed in the magnocellular pathway.…”

“…This measure may contribute to the diagnosis of amblyopia because the proportion of eyes with NDF-induced suprathreshold depression is greater for normal control eyes than for amblyopic eyes. 32 For these reasons, here we aimed at determining whether human visual function assessment could be optimized by using an extended electrode array, including 64 electrodes of an extended 10-20 system, with four additional electrodes in the occipitotemporal region.…”