Ptosis Sensitivity Threshold for the Lay Observer

Purpose This study aims to understand the degree to which ptosis is recognizable to a layperson. Methods Fifteen color drawings of a gender-neutral human face were created. Six faces exhibited right-sided ptosis (decreased margin reflex distance 1 and lengthened tarsal platform show) of 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm, respectively. Six more faces exhibited left-sided ptosis of the same amounts. The 12 ptotic faces and 3 symmetrical faces were randomly placed on three 11-inch by 14-inch sheets of paper with 5 faces on each page. Lay observers were provided 6 seconds per face to indicate whether it appeared to be asymmetrical. Statistical tests examined the observers' ability to detect asymmetry better than chance. Sex differences in correctly recognizing asymmetry in ptosis at each 0.5 mm increment were analyzed. Results One hundred thirty-one lay observers were enrolled in the study. Fifty-seven were women and 74 were men. Lay people were able to correctly recognize ptosis better than chance when the asymmetry was 1.5 mm or greater. Moreover, females were more accurate in recognizing ptosis at 1.5 mm, 2.0 mm, and 2.5 mm of asymmetry. Conclusions Lay observers tend to recognize between 1.0 mm and 1.5 mm of ptosis on one side as being abnormal. This may have implications in the selection of candidates for ptosis surgery and the analysis of subsequent surgical outcomes.