[Clinical and experimental study of traumatic optic nerve damage].

BACKGROUND

Traumatic optic nerve lesions (TONL) range from temporary affection of vision to avulsion of the optic nerve; often they are associated with more complex injuries. Usually Tonl are not regarded as an emergency. Up to now, we lack knowledge on the dependency of strength and duration of optic nerve lesions and the point of no return for afferent disorders of the visual pathway.

MATERIALS AND METHODS

We performed a prospective study on 50 patients with severe midface and skullbase fractures in order to find characteristic ophthalmological, computer tomographic und electrophysiological findings as indicators of TONL, independent of patient cooperation. We used an animal model (Wistar rats; n = 117) to study calibrated optic nerve lesions and the resulting neurodegeneration in the retinal ganglion cell (RGC) layer quantitatively.

RESULTS

The electrophysiological investigation of the visual system (flash VEP/ERG) proved to be highly specific (0.97) and sensitive (1.0) for detecting TONL (n = 18). In the rat model, we could demonstrate a linear relationship between total neuron number reduction and strength and duration of calibrated optic nerve lesion.

CONCLUSIONS

Experimental results indicate that optic nerve decompression is useful only within the first hours after TONL to reduce secondary optic nerve lesion. Indication for optic nerve decompression requires early detection of TONL, which is made possible by the combination of flash VEP/ERG.