A Clinical Case from the Archives : 03/11/2006

Sorry this isn’t the best picture in the world but it shows what I saw well enough. This nine year old cross-bred has a positive swinging light test into its right eye (a Marcus-Gunn pupil for those of you liking eponyms!). The pupil in the right eye dilates as the light is directed into it showing that there is less ipsilateral stimulation than from the contralateral eye. The dog has had GME with involvement of the prechiasmal optic nerve and now has an optic nerve head looking like this. What can you see and can you work out what has happened?

Here is the normal optic nerve head on the contralateral side. Note how the entire cribriform plate is taken up by myelinated nerve fibres unlike the affected eye. I presume that the smaller size of the affected nerve has been caused by optic nerve degeneration. But is that right? Have you seen something similar?


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