To the Editor:

Zhu et al. [1] report a series of 62 acute acquired concomitant esotropias (AACE) being more prevalent in younger adults and associated with excessive near visual activity and late-night use of digital devices.

We have also seen a marked increase in the presentation of AACE in recent years in the paediatric population. Quantifying near visual activity and screen/smartphone use is hampered in this age group by lack of awareness or unwillingness to admit prolonged periods of near digital device use. Often there is a quick look toward their parent/carer before answering any questions about screen use, suggesting reticence in admitting the true picture.

The increase in AACE has been particularly marked during the Covid-19 pandemic: we have recorded a doubling of incidence in our centre. Over a 4-year period we identified 18 consecutive cases of AACE: 6 between 2018–19 (24 months pre-pandemic) and 12 between 2020–21 (24 months of pandemic). 11 males and 7 females aged between 9 and 17 years (mean 12.5 years) were treated. In contrast to Zhu et al’s [1] cohort, only 2 young people were myopic in our series, 2 were wearing their full hypermetropic correction and the remainder were emmetropic with no latent hypermetropia on cycloplegic refraction. One case had resolution of their AACE with complete abstinence of near screen use; the others all received 2.5IU botulinum toxin (Botox, Allergan, Irvine, CA, USA) into one (n = 2 with a predominantly unilateral squint) or both medial rectus muscles under GA. Significant temporary ptosis was reported in 20% and initial exotropia in 40%. All achieved straight eyes with no diplopia within 6 weeks. Normal motor and sensory fusion were re-established in all cases. Follow-up ranged from 3 months to 4.5 years (average 16.4 months). Three young people re-presented with an esotropia after 2+ years of straight eyes and were offered further botulinum toxin or strabismus surgery.

We recommend botulinum toxin injection into the medial rectus as a safe, quick and effective treatment of AACE prior to considering surgical management. Public health information on the risks of prolonged near screen use may encourage prevention.