UNSATISFACTORY TREATMENT OF ACQUIRED NYSTAGMUS WITH RETROBULBAR INJECTION OF BOTULINUM TOXIN

PURPOSE: We quantified the effects of botulinum toxin injected into th e retrobulbar space of patients with acquired nystagmus with prominent vertical or torsional components. METHODS: We measured binocular eye rotations in three planes before and after injection of botulinum toxi n (10, 12.5, or 25 units) into the retrobulbar space of one eye of eac h of three patients, ages 28 to 37 years, with acquired pendular nyse tagmus. RESULTS: Retrobulbar injection of botulinum toxin abolished or reduced all components of the nystagmus in the treated eye in all thr ee patients for about two to three months. The patient who received 25 units developed complete external ophthalmoplegia and blepharoptosis. The other two patients retained some voluntary movements but develope d diplopia. In one patient, visual acuity improved from Jaeger 5 to Ja eger 1. In a second patient, filamentary keratitis developed, and visu al acuity declined from Jaeger 2 to Jaeger 7; keratitis was a recurren t problem one year after the botulinum toxin injection. In the third p atient with predominantly torsional nystagmus, visual acuity was uncha nged at Jaeger 2. No patient was pleased witch the results, because of blepharoptosis, diplopia, or discomfort (from keratitis), and none el ected to repeat the procedure. CONCLUSIONS: The side effects of botuli num toxin administered by retrobulbar injection limit its therapeutic value in the treatment of acquired nystagmus. Even smaller doses that do not abolish nystagmus may produce troublesome diplopia.