Clinical Application Of Intense Pulsed Light Technique On Facial Photoaging: A Randomized Controlled Split Face Trial

ObjectivePhotoaging is caused by chronically sun exposure and characterized with fine and coarse wrinkles,roughness,driness,laxity,dyspigrnentations,telangiectasia,et al. Among the nonablative rejuvenation techniques,intense pulsed light(IPL)treatment has great advantages over others.Owing to the long period of IPL treatment,various factors such as season,cosmetic,skin color and driness degree may affect the treatment and the assessed results.The present study innovatively used split face model to observe the clinical effect of IPL treatment on facial photoaging.Histological stain were used to explore the possible mechanisms.Materials and Methods1.SubjectsA total of 41 female photoaging patients who were diagnosed by well-trained dermatologists and had symmetrical lesions on both sides of each face were enrolled in this study.The face of each subject was randomly divided into treatment side(four session of IPL treatment were applied)and untreatment side(no treatment were applied temporally).Four weeks after the final treatment of the treatment side,the skin biopsies of both face of ninteen subjects were taken and ice sections or paraffin sections were produced.2.Preparation of treatment and treatment procedure (1)Preparation of treatmentAn informed consent was signed by each subject.Before treatment,subjects were required to rinse their face thoroughly with a neutral lotion,and rest in the temperature-controlled(20℃)and humidity-controlled(40-50%)room for at least 30 minutes.Standardized photographs were taken with a digital camera.(2)Treatment procedureFour sessions IPL treatment at 3-4 weeks intervals were applied to the treatment side.The treatment parameters were modified according to the patients' Fitzpatrick skin type,skin color,quality,site or density of lesions.Cut-off filters of 560 nm,590 nm,and 640 nm were employed.The energy fluency ranged from 11-18 J cm^-2.A single,double or triple pulse mode of pulse,with a pulse width of 2.5-4ms and a delay time of 20-40ms were utilized.A chilled colorless gel of 2-5mm in thickness was applied to the treatment area before each shot.The treatment endpoint was slight erythema.After treatment,the patients were required to wash their face with cold water and received the cold-wet compress with a soothing spring water for 5-10min.The treatment procedure last 10-20min.The patients were advised to avoid sun exposure and apply sun screen(SPF≥30)and moisturizer after each treatment.3.Evaluation Criteria(1)Subjective evaluation by the dermatologistsAssessment of global scores(ranging from 0-4 score)for photoaging was performed by blind dermatologists before each session,4 weeks after the final session and at the 3-month follow-up visit.Fine lines,roughness and dyspigmentation of both facial sides(each side including three area:cheekbone,forehead,perioral area)were assessed.(2)Patients' self-assessmentFour weeks after the final treatment of treatment side,the subjects were asked to rate the results as excellent(very satisfied),good(moderately satisfied),fair(slightly satisfied),or poor(not satisfied at all). (3)Objective evaluation①Invasive evaluationSkin melanin index(MI)and erythema index(EI)of five sites on both facial sides: forehead,canthus,cheekbone,cheilion,and submaxilla were measured before each session,4 weeks after the final session and at the 3-month follow-up visit.Each site was measured five times and the mean value was counted.At the same time,the surface water content of cheekbones on both sides was measured.Each site was measured ten times and the mean value was counted.②Evaluation of biopsy skinWith L-DOPA stain for paraffin sections,the numbers of dopa-positive melanocytes were counted and using the immunohistochemistry stain,the numbers of NK1β-positive melanocytes were counted.With Schmorl stain and Fontana Manna stain,the numbers of cells containg melanin and melanin content index(MCI)were counted.Hematoxylin-eosine stain,Verhoeff-van Gieson stain or double combination stain were used to observe the content of collagen fibers and elastic fibers.4.StatisticsThe data were analyzed with SPSS 11.5 soft ware package.Student t-test was used for normal distribution data and nonparametric statistical methods Mann-Whitney test were used for skewness distribution data.P-values＜0.05 were considered statistically significant.Results1.The effect of IPL treatment on subjective evaluation by dermatologistsNo differences were observed on the untreatment side at various times.On treatment side,compared with pretreatment,the global scores after each session decreased variably and significant differences were observed. 2.Patient self-assessmentEleven patients rated their results as excellent,twenty-six as good,and four as fair. No one unsatisfied with the treatment and the satisfactory rate reached 90.24%.3.The effect of IPL treatment on MI/EI values(1)MI/EI average valuesNo obvious differences were shown on the untreatment side at variou times. Compared with pretreatment,MI average values deceased significantly after the 1^st session,the 4^thsession and at the 3-months follow-up visit.Although EI decreased after all session at various degrees,but no difference was observed compared with pretreatment.(1)MI/EI difference valuesAfter each session,the MI difference values of treatment side were significantly bigger than those of untreatment side.The EI difference values of treatment side were obviously bigger than those of untreatment side after the 1^stsession,the 4^thsession and 3-month follow-up visit.4.The effect of IPL treatment on water content on the surface of skinComparing to pretreatment,no significant differences were observed between the untreatment side and treatment side.5.The effect of IPL treatment on the melanocytes and melanin content(1)No differences were observed between untreatment side and treatment side concerning of the linear density of dopa-positive cells or NK1β-positive cells.(2)Compared with untreatment side,the density of melanin content cells of IPL treatment side decreased obviously.(3)Compared with untreatment side,the measured percentage(%)and average optical density of MCI-1 and MCI-2 decreased significantly.6.The effect of IPL treatment on the collagen fibers and elastic fibers (1)Compared with untreatment side,the measured density percentage and average optical density of collagne fibers on IPL treatment side significantly increased(2)Concerning of the measured density percentage and average optical density of elastic fibers,no differences were observed between untreatment side and treatment side.The elastic fibers of untreatment side broken,irregularly arranged or gathered together,and those of treatment side basiclly paralleled with collagen fibers and wave-shape arranged.Conclusions1.IPL treatment could obviously decrease the subjective scores assessed by dermatologists and MI/EI values,with no influence on water content of statum.Patients were satisfied with the treatment.IPL is safe and effective in treating photoaing lesions including skin fine wrinkles,roughness,driness,uneven pigmentation,erythema and telangiectasis.2.IPL treatment could effectively remove large numbers of malanin in epidermis and thus alleviate the dyspigmentation of photoaging skin,with no influence on the activity of melanocyte.3.IPL treatment could increase the collagen fibers of photoaging skin and nomalize the arrangement of elastic fibers.So the content of collagen in skin could be resumed and the skin elasticity could be improved.