Visual loss with inner retinal dysfunction, after snake bite: two case reports

To report two cases of visual loss following snake bite.

Retrospective review of medical records including history, examination finding, fundus details and investigation reports (visual field, electroretinogram, visual evoked potential and optical coherence tomogram) at two centers.

Two cases of snake bite presented to us with reduction of vision at 1 and 3 months after the incident. The subnormal b wave and abnormal pattern electroretinography in one case pointed at inner retinal dysfunction and neurotoxicity as the cause of visual loss in an apparently normal-looking fundus. The electronegative b wave in the other gave us a clue that the optic atrophy was consecutive (secondary to inner retinal dysfunction due to central retinal artery occlusion).

When presented late, diagnosis of visual loss secondary to snake bite becomes difficult and puzzling due to the absence of classical findings. Electrophysiological tests in such cases give us important clue to reach at a definite diagnosis.