Exploring mandibular asymmetry: insights from visual perception using eye-tracking technology

The visual attention provides an objective perspective on how a stimulus take attention. In dentistry, one of the important facial determinants in esthetic perception is the mandibular asymmetry. The study aimed to evaluate the eye movements of the orthodontists and non-professionals on the images with different severity of mandibular asymmetry using eye tracking technology.

The eye movements of 26 orthodontists and 30 non-professionals were captured. Thirty images were visually evaluated for the presence of mandibular asymmetry by two orthodontists. 2 mm, 4 mm, 6 mm, and 8 mm chin deviation were simulated on the images and the images without asymmetry were considered as control group. A total of 50 photographs from 10 individuals were included in the study. Participants' eye movements were recorded using an Eyelink 1000 plus eye-tracking device (Sr-Research, Canada). Repeated Measures Analysis of Variance (ANOVA) was used for statistical comparisons.

The number of fixations on the lower lip-chin area in either the right or left direction did not show a statistically significant difference. (F(1,000;59,000) = 2.133, p > 0.05, ). Time to first fixation was faster to the lower lip-chin area in 8 mm asymmetry condition compared to 2 mm (F(1,2) = 31.423, p < 0.05, η_p² = 0.940). Orthodontists made less fixations before the lower lip-chin area in 8 mm condition compared to 2 mm (F(1,2) = 20.758, p < 0.05, η_p² = 0.912).

While the direction of mandibular asymmetry did not affect voluntary attention, an increase in asymmetry, regardless of profession, attracted more attention to the lower lip-chin area. While the 8 mm asymmetry caught the involuntary attention of orthodontists, the same did not occur in non-professionals.