RESUMEN
CLINICAL RELEVANCE: Botulinum toxin is commonly used for cosmetic facial rejuvenation and can result in pain at the injected site, bruising and ecchymosis, erythema and oedema, headache, diplopia, blurred vision, focal facial weakness. This study evaluates the impact of botulinum toxin on refractive error and binocular vision. BACKGROUND: Botulinum toxin (trade name: Dysport) is a neurotoxic protein which is made from a Gram-positive anaerobic bacterium known as Clostridium botulinum. In this study, we aimed to evaluate the impact of Dysport injection on refractive error, near point of accommodation and convergence, and palpebral fissure height. METHODS: Twenty-eight subjects were treated for facial wrinkles, using Dysport. A 500-unit vial of Dysport was diluted with 2.5-ml preserved normal saline, and injected doses were 30-units for crow's feet, six units for lower eyelid wrinkles, 25 to 50-units for glabellar lines (five points), and 20 to 40 for forehead creases on four points. The refractive error, near point of accommodation and convergence and palpebral fissure heights were assessed before and two weeks after injection. RESULTS: The participants comprised 23 women and five men at a mean age of 53.51 ± 14.1-years. The means of the equivalent sphere before and after injection were -0.07 ± 1.34 and -0.08 ± 1.35 (p = 0.36). The means of near point of accommodation monocularly before and after injection were 29.75 ± 6.16-cm and 26.75 ± 6.00, respectively. The means of near point of convergence before and after injection were 16.03 ± 5.27-cm and 15.55 ± 6.14, respectively (p = 0.30). The means of palpebral fissure height before and after injection were 10.33 ± 1.69-mm and 10.20 ± 1.46-mm, respectively. The changes in equivalent spherical refractive error, binocular near point of accommodation and convergence were not statistically significant. CONCLUSION: Dysport injection for the correction of upper face animation lines, if performed at the appropriate sites and the appropriate concentration, has no significant impact on refractive error, near point of accommodation and convergence, and palpebral fissure height.
