Development and Validation of a Photonumeric Scale for Evaluation of Infraorbital Hollowing

Background: The infraorbital hollow is characterized by a sunken hollowing appearance of the junction between the lower eyelid and the cheek. Dermal fillers provide a suitable option to reduce the appearance of infraorbital hollowing. To objectively evaluate treatment-related improvements in clinical practice and research, a validated photonumeric scale is needed. Objective: To present the scale development methods for the Merz Infraorbital Hollow Assessment Scale and establish its reliability and clinical relevance. Methods: A 5-point photonumeric scale was developed to objectively assess the infraorbital hollowing among subjects of varying sex, age, and skin type. Intra- and inter-rater reliability was evaluated using live assessments conducted 2 weeks apart. The clinical relevance of a 1-point difference in scale-severity grade was evaluated through side by-side comparisons of photographs with either same grade or a one-grade difference. Results: The scale demonstrated excellent reliability when used by trained physicians and other healthcare practitioners. Intra-rater agreement between the 2 live-subject rating sessions was nearly perfect. Substantial inter-rater agreement between the raters from both live sessions was also demonstrated. The mean absolute difference (95% confidence interval) in scale ratings was 1.08 (1.02, 1.14) for "clinically different" pairs and was 0.34 (0.27, 0.41) for "clinically same" pairs, suggesting a 1-point difference is clinically relevant. Conclusion: The Merz Infraorbital Hollow Assessment Scale is a validated, reliable, and clinically relevant photonumeric scale for rating infraorbital hollowing. The scale maintains its validity and reliability with reproducible results across a diverse group of males and females of various ages and Fitzpatrick Skin Types.