Accuracy of Marginal Reflex Distance Measurements in Eyelid Surgery

The marginal reflex distance (MRD), the position of the eyelids with the eyes in the primary position, is fundamental to patient assessment and surgery choice in facial and ophthalmic plastic surgery. This study compares the accuracy of handheld ruler and slit lamp biomicroscope measurements of the MRD1 in patients with blepharoptosis.This is a prospective study of 85 consecutive patients who were referred to our oculoplastic clinic between 2011 and 2013 for unilateral or bilateral ptosis repair. The MRD1 was measured by 2 techniques: 1. With the use of a penlight to illuminate the cornea, the corneal light reflex is observed, and the distance between the cornea and the upper lid margin is recorded. 2. Slit lamp biomicroscope assessment. A comparison between those 2 methods was performed.The mean (SD) MRD1 was 1.18 (1.11) mm and 1.06 (1.18) mm with a penlight and a slit lamp, respectively. There was a significant difference between the 2 measurements, but they were highly correlated in the paired t-test and the Wilcoxon test. The intraclass correlation coefficient was 0.984, representing excellent reliability.The MRD1 measured by a skilled clinician yields reliable results using a penlight and a ruler. In some cases, measurement of eyelid heights (palpebral fissure, MRD1, brow position) is challenging. The use of a slit lamp biomicroscope and a close front photograph may help determine accurate measurements.