Is Eye Color Related to Dental Injection Pain? A Prospective, Randomized, Single-blind Study

Introduction: Recent studies have investigated the relationship between pain perception and specific phenotypes such as red hair color and various eye colors. Further investigations into biomarkers as they relate to pain could be useful in understanding underlying genetic components involved in these pathways. Additionally, it would be clinically useful to determine if a patient would be more likely to experience pain during dental treatment based on eye color. The purpose of this study was to investigate a link between eye color and perceived injection pain in healthy, asymptomatic white women. Methods: Three hundred healthy, adult, white female patients were included, 133 with dark eyes and 167 with light eyes. Dental anxiety was assessed with the Corah Dental Anxiety Scale. Subjects with their eye color masked by dark glasses received a right maxillary lateral incisor infiltration of 1 cartridge of 2% lidocaine with 1:100,000 epinephrine. Patients rated their injection pain on a 170-mm Heft-Parker visual analog scale. Photographs of the subjects' eyes were taken after the infiltrations and categorized into dark- and light eyed groups by 3 independent observers. Comparisons for injection pain were analyzed using analysis of variance and the Tukey-Kramer test. Results: No significant differences were found for pain of injection between dark- or light-eyed subjects. Conclusions: Eye color was not shown to be a predictor for injection pain in white women. Therefore, eye color would not be clinically useful in determining if a patient would be more likely to experience pain during dental treatment.