Researchers and clinicians already know that botulinum toxin, commonly used for cosmetic facial rejuvenation, can result in pain at the injected site, bruising and ecchymosis, erythema and edema, headache, diplopia, blurred vision and focal facial weakness. But one thing it doesn’t seem to affect is refractive error, according to a recent study. When performed at the appropriate sites and the appropriate concentration, injections have no significant impact on refractive error, near point of accommodation and convergence and palpebral fissure height, the researchers found.

A 500‐unit vial of Dysport (abobotulinum toxin A, Ipsen), was diluted with 2.5ml preserved normal saline. The study administered in 28 participants (23 females, five males) who were treated with 30 units for crow's feet, six units for lower eyelid wrinkles, 25 to 50 units for glabellar lines and 20 to 40 units for forehead creases.

The researchers did not find any changes in equivalent spherical refractive error, binocular near point of accommodation and convergence as statistically significant. The means of the equivalent sphere before and after injection were -0.07 and -0.08. The means of near point of accommodation monocularly before and after injection were 29.75cm and 26.7cm, respectively. The means of near point of convergence before and after injection were 16.03cm and 15.55cm, respectively. The means of palpebral fissure height before and after injection were 10.33mm and 10.20mm, respectively.

The study concluded that botulinum toxin did not have a negative impact on refractive error and binocular vision.