Acquired blepharoptosis secondary to essential blepharospasm.

We treated four patients with essential blepharospasm, receiving botulinum A toxin, in whom, although they had no preexisting blepharoptosis, a concurrent bilateral acquired blepharoptosis developed. Since the blepharoptosis did not improve after the period of time during which the effects of botulinum A toxin would have been expected to resolve (2 to 10 weeks), we judged that its development was unrelated to the toxin. We propose, rather, that the stretching, attenuation, disinsertion, or dehiscence of the upper eyelid levator muscle caused by the blepharospasm were at least partly responsible for the onset of the blepharoptosis. To ensure appropriate treatment in these cases, careful clinical evaluation is required to differentiate the two conditions.