Role of botulinum toxin A in treatment of intractable diplopia

To evaluate the effect of botulinum toxin A (BTXA) in patients with intractable diplopia related to intracranial problems or long-term interruption of fusion due to cataract or uncorrected aphakia and to identify the group of resistant cases who have no potential to fuse the two images.

The medical records of patients seen by the senior author (SBÖ) over a period of 20 years were reviewed retrospectively to identify those who underwent BTXA treatment for intractable diplopia. All cases had horizontal and/or vertical deviations. The diagnostic criterion was persistence of diplopia in free space despite neutralization of the deviation by prisms or synoptophore. BTXA was injected into the appropriate extraocular muscle to control the deviation in the identified patients.

A total of 22 patients were identified: 13 developed intractable diplopia following head trauma, intracranial surgery, or stroke; 9 had a history of binocular sensory deprivation due to traumatic cataract or uncorrected aphakia. The duration of sensory deprivation ranged from 2 to 41 years. BTXA was injected into the appropriate extraocular muscle(s). Diplopia resolved completely in 14 patients, resolved incompletely with short-term single vision in 3 cases, and persisted in 5 patients despite correction of the deviation by BTXA.

Our results suggest that BTXA offers the advantage of a temporary decrease of the deviation without altering image quality that allows the visual system to recover fusion under real-life conditions. Permanent treatment with surgical correction of the deviation should be reserved for those who achieve fusion during the orthotropic period provided by BTXA.