A trial of a mechanical device for the treatment of blepharospasm

Abstract

Idiopathic blepharospasm (IB) is a rare but well-characterised adult onset focal dystonia that may cause severe visual disability. The most effective treatment is with periodic injections of botulinum toxin (BTX) into the pre-tarsal and/or pre-septal orbicularis oculi muscles bilaterally. However, even with treatment, practical visual function often remains compromised. A subset of IB sufferers find that eye opening improves with a focal unilateral digital pressure usually on a specific point on the temple. This is known as a ‘sensory trick’. We have developed a spectacle mounted device (‘Pressop’) to apply continuous individually localised focal pressure on the temple to mimic the effect of finger pressure. The aim of the study was to determine if the ‘sensory trick’ could be replicated by Pressop and if the interval between BTX treatments could thereby be extended. Study participants had three clinic visits—an initial screening assessment, a visit 2 weeks before the next injection was due when the device was fitted, and one 2 weeks later to assess the response to Pressop. A CDQ 24 and device-specific feedback questionnaire were completed and comparison photographs were taken. Repeat BTX injections were administered at the third visit. Of 58 patients with typical IB recruited to the trial, 39 reported an effective focal finger pressure sensory trick. 56 completed the trial, more than 50% of whom reported some benefit using Pressop; 18% had substantial improvement, sustained for up to 5 years. Improvement could occur in those without an effective sensory trick, therefore there was no significant correlation between using a sensory trick and benefiting from ‘Pressop’. There was a trend towards the responders having greater improvement in CDQ24 total score than non-responders but this was not statistically significant. We recommend a trial of this simple safe device as a means of augmenting visual function in all IB patients.