Beyond Aesthetics: Imaging-Based Evaluation of Carboxytherapy in Periorbital Hyperpigmentation

Background: In this study, we radiologically assessed potential increases in microvascularity, extracellular matrix-related changes, and tissue viscoelasticity following carboxytherapy for periorbital hyperpigmentation (POH). We also analyzed the correlation between radiological changes and clinical outcomes and explored implications for future outpatient selection, as well as the potential to predict treatment success based on radiological-clinical correlations. Materials and Methods: The present study included 78 patients (76 women and 2 men) aged over 18 years with Fitzpatrick skin types I-V and moderate-to-severe infraorbital dark circles who applied for treatment at the Dermatology Department in the Cosmetology Unit of Cerrahpaşa Medical Faculty Hospital. Each patient was given manual, pressure-controlled injections of sterile CO₂ into the upper and lower eyelids for 7 weeks, with one round of treatment per week. We conducted dermatoclinical and radiological evaluations, including measurements of epidermis-dermis thickness and SWE, musculus orbicularis oculi pars pretarsalis thickness, and cSMI vascular index percentage, as well as SOOF tissue SWE (measured in kPa). These analyses were performed on both lower eyelids before treatment and at 1 month and 6 months after treatment. Results: After treatment, VAS scores improved significantly. Grayscale ultrasonography showed significant increases in epidermis-dermis and orbicularis oculi thickness at 1 and 6 months (p < 0.05). SMI presented a significant increase in vascular index at both follow-ups (p < 0.05). SOOF SWE values increased significantly at 1 and 6 months, whereas epidermis-dermis SWE did not. Procedural pain was common, and 25 participants withdrew during the 7-week period due to discomfort. Injection depth was not confirmed by real-time imaging, and adverse events were not graded using a standardized classification system. Therefore, tolerability and procedural safety should be interpreted with caution. Conclusions: Carboxytherapy was associated with improvements in clinical outcomes and radiological parameters among patients who were able to tolerate the procedure, including increased microvascularity on SMI and changes suggestive of extracellular matrix-related alterations. These improvements were maintained at the 6-month follow-up, indicating temporal persistence of the observed findings. However, due to the absence of a control group, the results should be interpreted with caution, and further randomized controlled studies are required to confirm these findings and establish causality.