CARBON-MONOXIDE POISONING CAUSES OPTIC NEUROPATHY

Purpose To describe the electrophysiological and psychophysical effect s of carbon monoxide (CO) poisoning on visual function. Methods Three patients are presented who suffered CO poisoning, two due to suicide a ttempts and one in the course of a road traffic accident. After a full ocular examination, Goldmann visual fields, flash and pattern visual evoked potentials (VEPs) and flash and pattern electroretinograms (ERG s) were tested. Results Electrophysiology showed reduced or absent N95 components of the pattern ERG and delayed, reduced VEPs. A positive-n egative-positive (PNP) VEP waveform was seen in two cases. In one case , where presentation occurred at an early stage, visual and electrophy siological function was improved with hydroxycobalamine. Conclusions T he combination of ERG and VEP findings suggest that CO poisoning can c ause a toxic optic neuropathy that may have a similar aetiological mec hanism to that in tobacco amblyopia. Early treatment with hydroxycobal amine may be of some benefit.