Hering's Law in Congenital Ptosis: Evaluation of the Contralateral Response to Unilateral Congenital Ptosis Repair.

Purpose: To determine the applicability and clinical relevance of Hering's law for the eyelids in cases of congenital ptosis.

Methods: A retrospective chart review and digital photograph analysis of patients who underwent unilateral congenital ptosis repair at a tertiary, university-based, Oculoplastics clinic was conducted. Pre- and postoperative eyelid height (marginal reflex distance), upper eyelid symmetry, and brow position were determined using ImageJ analysis software. Changes in these values, and the relationship between the change in ipsi- and contralateral eyelid heights and brow positions, were determined.

Results: In 51 patients, the mean change in contralateral upper eyelid position (marginal reflex distance) following unilateral repair was -0.5 mm with 29% (n = 15) demonstrating a greater than 1 mm contralateral descent. The contralateral brow position remained stable with a mean change of +0.1 mm. No significant differences were seen between the 15 patients who demonstrated a contralateral upper eyelid descent greater than 1 mm and the remainder of the cohort in terms of amblyopia rate (p = 0.71), mean preoperative marginal reflex distance (p = 0.14), mean change in ipsilateral marginal reflex distance (p = 0.32), mean change in contralateral brow position (p = 0.44), or mean postoperative upper eyelid asymmetry (1.3 mm vs. 1.2 mm). Overall, the mean upper eyelid asymmetry improved from 2.6 mm preoperatively to 1.2 mm postoperatively. None of the 51 patients underwent subsequent contralateral ptosis repair.

Conclusions: Hering's law for the eyelids applies to cases of congenital ptosis but has little clinical significance due to improved upper eyelid asymmetry following unilateral surgery.