Is Hering's law as important in congenital blepharoptosis as in acquired ptosis?

Background: Although Hering's law has significant importance in the planning and outcomes of eyelid surgery, it has not been applied in all cases of ptosis.

Objective: The authors evaluate whether cases of unilateral congenital ptosis require surgery on the contralateral eyelid, in keeping with Hering's law.

Methods: The records of 35 consecutive patients with unilateral congenital ptosis who had surgical repair between 2007 and 2012 were retrospectively analyzed. All patients underwent either levator resection or frontalis sling surgery. Preoperative and postoperative clinical documents and photographs were evaluated for each case, including preoperative Hering's dependence and postoperative measurements of the change in position of the nonoperated eyelid.

Results: There were 19 women and 16 men, and the average patient age was 9.7 ± 10 years. The mean preoperative levator function and marginal reflex distance were 6.7 ± 4.7 mm and 0.3 ± 0.47 mm, respectively. There were significant differences in age, preoperative levator function, and marginal reflex distance between patients who underwent levator resection and those who had frontalis sling surgery. In all patients, the preoperative Hering's dependence of eyelid position did not show any decrease, and the position of the contralateral eyelid postoperatively did not differ from the baseline position.

Conclusions: This research shows that Hering's law does not apply to cases of congenital ptosis. This is likely due to the fibrotic levator palpebrae muscle and its special innervations. Thus, it is not necessary to perform levator resection or a frontalis sling operation on the unaffected eyelid.