Validation of a new photogrammetric technique to monitor the treatment effect of Botulinum toxin in synkinesis

Abstract

Aims To validate a new photogrammetric technique for quantifying eye surface area and using this to quantify the degree of improvement in symmetry in patients with oral-ocular synkinesis following Botulinum toxin injection. Study design Feasibility study and retrospective outcomes analysis Methods Ten patients' photographs were chosen from a photographic database. Their eye surface areas were measured independently by two raters using a graphics tablet. One rater repeated the procedure after 15 days. Bland-Altman plots were computed, ascertaining inter-rater and intra-rater variability. The eye surface areas of 19 patients were then derived from photographs taken before and after Botulinum toxin injections. Paired t-tests were used to analyse the significance of the difference in pre-and post-treatment symmetry. Results Ninety per cent of eye surface areas derived from the two raters were within a coefficient of variation of 0.1 (95% CI: 0.05-0.15). Similarly, 90% of eye surface areas derived from one rater had a coefficient of variation of 0.08 (95% CI: 0.04-0.12). Botulinum toxin significantly reduced synkinesis resulting from lip puckering, Mona Lisa smiling and Hollywood smiling (Po0.05).Conclusions We have proposed a clinically valid tool for quantifying the effects of Botulinum toxin treatment for oral-ocular synkinesis. We recommend this method be used to monitor the response of such patients when receiving Botulinum toxin treatment.Level of evidence 2c.