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RESEARCH PRODUCT

Optic neuropathy caused by type A botulinic toxin

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Purpose To report the development of an optical neuropathy after injection of type A botulinic toxin in a subject with blepharospasm. Methods Optical neuropathy was evaluated through a complete ophthalmologic examination consisting of bio-microscopy, tonometry and study of visual sharpness, colour test, visual field, OCT, fluorangiography and determination of VEPs. Results Intravenous therapy was begun with Metilprednisolone (20 mg/Kg/day) and Vitamin B6 associated with oral Citicoline, and there was a clear improvement down to normalization of the symptoms. After 6 months the Humphrey computerized visual field with central 30-2 program threshold test emphasised in ODx an upper half-field arc-shaped defect starting from the optical papilla and also affecting the fixation zone, while for the left eye the perimeter picture was always normal. Optical coherence tomography (OCT) examination of the peripapillary nervous fibres and of the head of the optical nerve highlighted a reduction in thickness of the papillary fibres with a rim area of 0.011 compared to the contralateral side, which presented a normal thickness of the fibres and a rim area of 0.026. The colour test was normal and the speed of execution of the test proved to be equal in the two eyes. Conclusion The authors draw attention to the need for correct administration of the botulinic toxin in the treatment of blepharospasm.