A recent study conducted in Brazil suggests that the use of botulinum toxin A (Botox) injections to treat hemifacial spasm (HFS) may have an added benefit – a reduction in unilateral eyelid spasms and intraocular pressure (IOP). Hemifacial spasm is a condition characterized by involuntary muscle contractions on one side of the face, often involving the eyelids and cheeks.
The study, led by Sebastião Cronemberger, MD, of the Federal University of Minas Gerais in Belo Horizonte, Brazil, is the first to employ a digital transpalpebral tonometer called Diaton to measure the impact of blepharospasm on IOP before and after Botox-A treatment. The results were published in the journal International Ophthalmology.
The study's findings show that before Botox-A treatment, patients with HFS had higher IOP in the affected eye compared to the contralateral eye (11 ± 3.42 mm Hg vs. 9 ± 2.98 mm Hg). However, post-Botox-A injection, no significant difference in IOP was observed between the two eyes, as measured by the Diaton (P=0.204) and the Goldmann applanation tonometer (GAT; P=0.971).
Elevated IOP is a key modifiable risk factor for glaucoma. The study's authors noted that involuntary blepharospasm has been linked to increased IOP. Therefore, individuals with HFS who are either suspected of having or have been diagnosed with glaucoma should continue to undergo periodic assessments after receiving Botox-A treatment.
While the study results may not drastically change clinical practices, they do raise awareness regarding the potential effect of elevated IOP in individuals with HFS. It highlights the importance of considering possible IOP elevation during glaucoma screenings for those with hemifacial spasm.
However, Drew Carey, MD, of the Wilmer Eye Institute at Johns Hopkins Medicine, cautioned that ostensible IOP elevation in some cases may be influenced by the measurement technique. He emphasized that most HFS patients would receive Botox injections anyway for symptom relief.
The study does offer evidence that Botox injections are not only effective in reducing spasms but also in lowering IOP, thereby enhancing patients' quality of life. Nevertheless, the study's authors acknowledge the need for further research to address certain questions, such as whether untreated patients would develop glaucoma or if IOP would naturally decrease due to increased aqueous drainage as a result of the spasms.
In this single-center study, 27 patients with moderate-to-severe HFS underwent IOP measurements both before and after Botox-A treatment, which is the first-line therapy for HFS. The study excluded patients with ocular hypertension or glaucoma. The short-term follow-up, the rarity of HFS, and the absence of pre-injection GAT measurements are among the study's limitations.
This study contributes valuable insights into the multifaceted relationship between hemifacial spasm, intraocular pressure, and the impact of Botox-A treatment. It underscores the importance of considering IOP management for individuals with HFS as part of their overall eye care.
Reference:
Trindade, D. P. V., Cronemberger, S., Veloso, A. W., Cardoso, F. E. C., & Osaki, T. H. Influence of unilateral eyelid spasms and botulinum toxin treatment on intraocular pressure measured by transpalpebral tonometer. International Ophthalmology,2023. https://doi.org/10.1007/s10792-023-02898-6