Abstract
Abstract: :
Purpose: We propose a novel role for Botulinum toxin (Botox®) induced blepharoptosis to treat childhood amblyopia. We evaluate the efficacy and safety of superior eyelid injection of Botulinum toxin to produce visually significant blepharoptosis in a primate model. Methods: For baseline measurements 5 conscious unsedated adult macaques were photographed and after sedation examined by slit lamp (SLE) including a 1 minute unanaesthetized Shirmers test. Under sedation Botulinum toxin (20, 30, or 50 units), dissolved in 0.9% NaCl solution, was injected through the skin of the left superior eyelid, inferior to the lid crease near the tarsal insertion of the levator aponeurosis. Photographs were taken on a weekly basis; SLE and Shirmers tests were performed biweekly. Lid fissures were measured from photographs and SLE. Medial canthal angles (MCA), defined as the angle formed between the superior lid margin apex, the medial canthus, and the inferior lid margin nadir, were measured from photographs. Evidence of visual axis obstruction was noted in each photograph and at SLE. Visually significant ptosis was defined as >50% obstruction of the visual axis. As a control, the right eye was not manipulated. Results: By day 4, all dosages of botulinum toxin produced visually significant ptosis. Maximum ptosis occurred at 4 d when lid fissures were narrowed by 75–95% and medial canthal angle measurements narrowed from 67.28° –90.48° at baseline to 0°–10.91°. Lid fissure measurements at SLE corroborated with the photographic data. Lid fissures decreased from 5–6 mm at baseline to 0–2 mm week 1 after injection. Visually significant ptosis lasted 13– 40 days. Eyes treated with 30 units recovered between 13 and 30 d while eyes treated with 50 units recovered at 40 d. The visual axis became <50% obstructed between 58.19% and 53.05% of maximal lid closure. No ptosis was noted in the contralateral eye at any time point. Shirmers testing demonstrated no discernable pattern of dry eye or excessive tearing attributable to botulinum toxin or ptosis. Conclusions: Temporary, reversible, visually significant ptosis follows injection of Botulinum toxin. Effects on medial canthal angle corroborated lid fissure measurements. While onset of ptosis was uniform at all doses, recovery of ptosis was dose dependent. Botulinum toxin may be a practical alternative in the treatment of childhood amblyopia.
Keywords: amblyopia • eyelid • pharmacology