A validated grading scale for crow's feet

To develop the Crow's Feet Grading Scale for objective quantification of the severity of lateral canthal lines and to establish the reliability of this photonumeric scale for clinical research and practice. A 5-point photonumeric rating scale was developed to objectively quantify the severity of lateral canthal lines at rest and at maximum contracture of the orbicularis oculi. Nine experts rated photographs of 35 subjects, twice, with regard to the aspect crow's feet in comparison with morphed images. Inter- and intrarater variability was assessed by computing intraclass correlation coefficients. The agreement between the experts was significantly high. Furthermore, the test-retest correlation coefficients were high for each expert after an overnight interval, demonstrating low inter- and intraevaluator variability. The 5-point photonumeric scale generated spans the severity of the type of crow's feet for which patients most commonly seek correction. The scale is well stratified for consistent rating.