Do blinking parameters in essential blepharospasm patients become similar to normal subjects after botulinum toxin injections?

Abstract

Purpose : A comprehensive analysis of blinking in essential blepharospasm (EB) rather than assessing the global eyelid movements (anomalous eyelid movements + blinking) frequency is clinically relevant to understand the complexity of this condition and the effect of treatment in blinking parameters. This study focuses on objectively evaluating blinking kinematics of EB patients before and after treatment, as well as comparing those parameters to controls.

Methods : Patients with moderate to severe disease and matching-age controls were enrolled. Patients were followed up before and 15 days after the administration of onabotulinumtoxinA (BTX). A high-speed camera and micro-LED were used to register a 3-minute video of eyelid movements (blinking + anomalous eyelid spasms). Movements correspondent to blinking were isolated and a custom-made software was used to objectively evaluate them. Outcomes were blinking frequency, mean amplitude of blinking and mean maximum velocity of eyelid closing (MVEC) during blinking. T-student tests were used to compare different groups and paired-t tests, to compare measurements before and after treatment in the EB group.

Results : 24 eyes from 12 patients with EB and 13 eyes of 13 control subjects were included in this study. Table 1 summarizes the findings (presented as mean ± standard deviation). Baseline EB blinking frequency was significantly higher (p<0.0001) and MVEC during blinking was significantly lower (p=0.0019), when compared to control subjects’, whereas a significant difference was not observed for blinking amplitude (p=0.6585) before treatment. After BTX injections, all parameters significantly reduced when compared to baseline measurements in the EB group (p=0.032 for blinking frequency; p<0.001 for amplitude and p<0.001 for MVEC). Although the blinking frequency significantly reduced after treatment, a significant difference was still observed, when compared to the control group (p=0.0195). Blinking amplitude (p=0.0098) and maximum velocity (p<0.0001) were significantly lower when compared to the control group.

Conclusions : Our results show that all assessed blinking parameters significantly differed from control subjects after treament, likely reflecting alterations due to the disease itself and due to the effect of botulinum toxin in orbicularis oculi muscle.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

 

Recording of the upper eyelid movements in a patient with blepharospasm.