1333 - Blurry Eyed and Squint-Deprived: A Surprising Outcome of Botox for Hemifacial Spasms

Case Diagnosis: Hemifacial Spasms

Case Description: A 72 year old woman presented with right facial hemispasms and was treated with botulinum toxin injections to the orbicularis oculi. Two weeks later, the patient developed blurry vision in the right eye. Two months later, the patient’s symptoms improved, and an ophthalmologic exam was performed and was unremarkable except for progression of known cataract formation and macular degeneration. These findings were unknown to us prior to her first injection cycle. The patient returned four years later for botulinum toxin injections due to persistence of the hemifacial spasms and had her cataracts excised in the interim. One month after the most recent botulinum toxin injections she did not report any blurry vision.

Discussions: Eyelid squinting is accomplished by contracting the orbicularis oculi muscle. The palpebral portion of the muscle extends through the eyelids and is responsible for blinking of the eyes. The orbital portion is responsible for drawing the brows and cheeks closer to the eyes and results in eyelid squinting. The literature suggests that eyelid squint improves distance visual acuity measures in the presence of refractive error by decreasing the size of the aperture stop which increases the depth of focus. Relaxing the orbicularis oculi with botulinum toxin can therefore have the side effect of causing blurry vision by impairing a person’s ability to squint especially in the setting of preexisting visual impairments.

Conclusions: It is important to ask patients with hemifacial spasms about pre-existing visual impairments prior to treatment with botulinum toxin injections to the orbicularis oculi. If patients develop blurry vision, an ophthalmologic exam is needed for further evaluation. Visual impairment may be due to impaired eyelid squinting which is known to improve visual acuity. With relaxation of the orbicularis oculi and reduced ability to squint, the patient may perceive objects as blurry.