Superior rectus underaction following botulinum toxin injection to induce protective upper eye lid ptosis – a comparative study of two techniques

Abstract

Background: Botulinum toxin A (BTXA) injection to the levator palpebrae superioris muscle to induce a protective ptosis can adversely cause reduced upgaze due to diffusion of BTXA to the superior rectus muscle.Purpose: To compare the incidence of reduced upgaze in trascutaneous versus transconjunctival administration of BTXA to induce protective ptosis in patients with exposure keratopathy due to facial nerve palsy.Methods: All patients included in this study suffered from acute exposure keratopathy and they all required chemodenervation of the levator muscle to induce a protective ptosis. Patients in group A received BTXA (Dysport) transcutaneously though the upper eyelid skin crease. Patients in group B received BTXA (Dysport) into the subconjunctival space at the superior border of the tarsal plate of the upper eyelid transconjunctivally. All subjects were closely monitored after BTXA injection and during each follow-up assessment the upper eyelid was lifted in order to uncover the effects on ocular motility. All patients had a follow-up of at least 1 year following injection of BTXA for their facial nerve palsy and its complications.Results: In group A, 20 patients were included. Reduced upgaze occurred in 9 patients (45%). Five required treatment with a Fresnel prism or ocular occlusion to avoid intractable diplopia. There were 15 patients in Group B, and only 2 of them developed post-treatment superior rectus underaction. One of these patients resolved spontaneously and the other patient required treatment with a spectacle-mounted Fresnel prism for diplopia. The difference in incidence of reduced upgaze between the 2 techniques was statistically significant (Fisher’s exact test, P = 0.0493).Conclusion: Injecting BTXA to induce protective ptosis via a transconjunctival supratarsal route was significantly less likely to induce superior rectus underaction than when given via the transcutaneous route.