Beware the Alar Base Optical Illusion in Assessment of Unilateral Cleft Lip Nasal Deformity.

Background: After repair of unilateral cleft lip, lateral drift of the alar base is expected and may require revision. Although the alar base appears wider than on the noncleft side, by measurement it could be symmetric or narrow. Is this an optical illusion? Methods: This is a retrospective photographic evaluation of children who underwent repair of unilateral complete cleft lip and palate. On submental standardized photographs, raters judged whether the alar base position was wider, equal to, or narrower than on the noncleft side. The true alar base position was measured by photogrammetry and the frequency of alar base misjudgment was assessed. On control photographs, the cleft side alar base was wider than the noncleft side. On test photographs, the cleft side alar base was narrower than the noncleft side. Possible association between misjudgment and nasal features was also evaluated. Data were analyzed using the Fisher's exact test. Results: Three raters assessed 61 patients aged 6 to 9 years and treated between 1995 and 2015. In 77 percent of control photographs, raters correctly judged the cleft side alar base as wider. In 65 percent of test photographs, raters incorrectly judged the alar base position as wider on the cleft side. Asymmetry of nostril outline and a transverse nostril axis were associated with misjudged photographs (p < 0.05). Conclusions: Alar base assessment can be altered by an optical illusion. Simple anthropometry counters this misperception. Measurement should be repeated after correction of the deviated anterocaudal septum and elevation of the lower lateral cartilage. Thereafter, a decision is made on altering the alar base position.