Levator Function Revisited; A Modified Assessment of Lid Movement to Better Identify Levator and Superior Rectus Synkinesis

Abstract

Purpose:: To propose a refinement in lid movement assessment with the introduction of a two phase approach to measuring levator function, and to demonstrate its effectiveness in identifying patients with levator-superior rectus synkinesis.

Methods:: Levator function was measured conventionally (total lid excursion from down gaze to up gaze) and by the two phase approach (phase 1: down gaze to primary position; phase 2: primary position to up gaze) in a group of 20 normal patients and in a consecutive series of 20 patients attending clinic with ptosis. For all measurements the brow was fixed to prevent lid elevation due to frontalis action.

Results:: As expected, when assessed in the conventional way those patients with normal lid position showed a normal range of levator function (mean 16mm) and those patients with ptosis had reduced levator function (mean 6mm).Using the modified two phase assessment of lid movement more information on levator function was obtained. In all patients with normal lid position the majority of lid movement occurred in phase 1. This was also the case in most patients with ptosis. However 3 patients with ptosis in primary position showed reversal of this pattern with lid movement in phase 2 being equal or greater than that in phase 1. These results can be explained by levator-superior rectus synkinesis, with recruitment of levator when the superior rectus function comes into play during up gaze.

Conclusions:: Conventional measurements of levator function (down to up-gaze) are relatively crude and fail to identify levator-superior rectus synkinesis; in these cases the levator function is overestimated with risk of the ptosis being under corrected at the time of surgery.By using a two phase assessment of levator function the subset of patients who have levator-superior rectus synkinesis may be identified. This technique also offers insight into the relative components of levator function and provides a more detailed method of recording lid movement.

Keywords: eye movements • eyelid • neuro-ophthalmology: diagnosis