388 JOURNAL OF COSMETIC SCIENCE the outcomes of most of them have been unsatisfactory (15). New modalities such as plasma gel (filler) and PDO threads may be promising in the aesthetic field in rejuvenation and treatment of POH (16). Use of PDO threads in POH is a revolutionary and novel technique with profound effects and minimal side effects. Its effect on POH could be possibly explained by collagen induction and the subsequent increase in skin thickness, resulting in altered optical properties of the formerly thinner skin. This could also decrease the sagging and laxity of the skin (17,18). This study aimed to evaluate and compare the efficacy and safety of PDO threads versus autologous plasma gel injections for infraorbital dark circles. The study included 40 adult male and female subjects with infraorbital hyperpigmentation. Blinded doctor assessment on a scale of 1 to 5 of patients’ responses after 1 month and after 6 months with PDO threads revealed a better response after 6 months compared with after 1 month, but without statistical significance. Plasma gel, on the other hand, revealed a significantly better response after 6 months compared with after 1 month. Using 3D Antera camera assessment of response with both treatments revealed that both PDO thread insertion and plasma gel injection exerted beneficial effects in periorbital rejuvenation. Both decreased texture roughness after 1 and 6 months, average melanin after 6 months, and average hemoglobin after 1 and 6 months. However, plasma gel revealed more potent effects compared with PDO threads. Suh et al. described PDO threads and techniques to counteract the descent and laxity of the face. They included 31 thread-lifting procedures. They concluded that facial rejuvenation using PDO threads is a safe and effective procedure associated with only minor complications, as most patients (87%) were satisfied with the results (19). Plasma gel exerts beneficial effects on facial wrinkles, and these effects are sustained over a long period of time post-treatment. This is explained by the fact that platelets are trapped in the injected area and continue to synthesize and release bioactive growth factors after Table IV Assessment of Treatment Response in Small-Sized Wrinkles with Both PDO Threads and Plasma Gel PDO threads response Plasma gel response The p value (after 1 month of both treatments) The p value (after 6 months of both treatments) After 1 month After 6 months After 1 month After 6 months Average melanin −0.019 ± 0.005 −0.013 ± 0.005 −0.023 ± 0.002 −0.023 ± 0.004 1.256 0.095 Average hemoglobin −0.003 ± 0.001 −0.014 ± 0.005 −0.05 ± 0.02 −0.04 ± 0.01 0.001 0.001 Table V Adverse Effects of PDO Threads and Plasma Gel Adverse effects Erythema Bruising PDO side 10 (25%) 4 (10%) Plasma gel side 17 (42.5%) 8 (20%)

389 Using the 3D Antera Camera for Accurate Evaluation injection. These growth factors interact with the undifferentiated adipose-derived stem cells and dermal fibroblasts, promoting neovascularization and neocollagenesis, which can increase skin thickness and improve skin sagging (20). Plasma gel injection also improves hyperpigmentary conditions through inhibition of melanogenesis via transforming growth factor β1 (21). To the authors’ knowledge, the current study is from the first studies that compared PDO threads and autologous plasma gel (filler) for infraorbital rejuvenation. Mehryan and colleagues assessed the efficacy of PRP injection for treating periorbital dark circles and crow’s feet in 10 patients with POH. The patients were administered a single injection of PRP, and the response was recorded using digital photography and skin surface analyzer. There was significant improvement in the infraorbital color homogeneity, but no changes were observed in pigment content, hydration of the skin, wrinkle size, and visibility index (22). Both PDO and plasma gel were safe with no serious adverse effects. These adverse effects include erythema and bruising. Erythema was mild, lasting for 1 to 2 days, and was associated with a mild burning sensation. It was more on the plasma gel side, and this could be a reactive reaction caused by the multiple injection sites of gel 0.5 mm apart. Bruising was more on the plasma gel side, and this could be related to the larger gauge used for plasma gel (27 G) to allow the passage of the thick gel while using 3–5 PDO threads with 30 G. POH is multifactorial in etiology. Treatment of periorbital wrinkles is a challenging task because of its anatomical significance and the delicate nature of the area. The treatment strategy depends on the etiology, and treatment must be individualized. PDO and plasma gel are safe tools that could improve POH and could be combined with other modalities to have a synergistic effect. CONCLUSION Both PDO thread insertion and plasma gel (filler) injection have beneficial effects in improving periorbital dark circles, hyperpigmentation, roughness, and vascularity. However, plasma gel revealed more potent effects compared with PDO threads. Infraorbital hyperpigmentation is a serious medical condition that deteriorates quality of life for suspected patients and makes them seek medical advice. Plasma gel filler is a new therapy that is easily and inexpensively prepared. PDO threads offer an important additional approach to rejuvenation and hyperpigmentation, especially in the periorbital region, with minimal adverse effects encountered in other aesthetic procedures and surgeries. REFERENCES (1) P. Mehryan, H. Zartab, A. Rajabi, N. Pazhoohi, and A. Firooz, Assessment of efficacy of platelet-rich plasma (PRP) on infraorbital dark circles and crow’s feet wrinkles, J. Cosmet. Dermatol., 13(1), 72–78 (2014). (2) F.M. Freitag and T.F. Cestari, What causes dark circles under the eyes? J. Cosmet. Dermatol., 6, 211–215 (2007). (3) R. Sarkar and A. Das, Periorbital hyperpigmentation: what lies beneath? Indian Dermatol. Online J., 9(4), 229 (2018).