the appearance of striae distensae ( sd ; stretch marks ) is an extremely common and well - recognized dermatologic condition that can lead to significant cosmetic concern for patients ( 1 ) . these atrophic dermal scars with overlying epidermal atrophy are found in all ethnic groups and are usually located on the buttocks , thighs , knees , breasts , calves , and lumbosacral areas ( 24 ) . the exact cause of sd remains unclear ; a combination of hormonal factors associated with mechanical stretching and rupture of connective tissue framework , tissue damage by striatoxin , pregnancy , normal growth ( especially in adolescents ) , rapid weight change , and high serum levels of steroids have been suggested ( 2,3,5 ) . clinically , immature sd are flattened , or slightly raised pink or red lesions ( striae rubrae ) . histopathologically , they appear as inflammatory alterations with elastolysis of the mid - dermis ( 3 ) and mast cell degranulation ( 6 ) . over time , and with atrophic changes , the lesions become white ( striae albae ; sa ) . histopathologic findings of this latter phase demonstrate epidermal atrophy and loss of the rete ridges ; densely packed , thin eosinophilic collagen bundles are arranged horizontally , parallel to the surface of the skin , similar to scars ( 6,7 ) . sd is not a medical problem , but can frequently pose a significant psychological burden for those affected . various therapeutic approaches [ topical tretinoin ( 9,10 ) , hydrant creams ( 11,12 ) , different acid peels ( 1316 ) , microdermabrasion ( 17,18 ) , and skin needling ( 19,20 ) ] have been proposed for the improvement of sd , with disappointing outcomes . thus , this common skin condition remains a frustrating concern for both physicians and patients . inspired by the success of various light and laser - based devices for the treatment of scars and rhytides , fractional lasers have been applied to the treatment of sd , in the hope of achieving similar efficacy . fractional treatment is achieved through a pattern of microscopic thermal zones produced by the laser beams at specific depths in the dermis . other modalities , such as intense pulsed light ( 21,22 ) , 585 nm flashlamp - pumped pulsed - dye laser ( pdl ) ( 23,24 ) , and radiofrequency devices have also been proposed ( 25,26 ) , with variable results . recently , non - ablative fractional laser ( 2731 ) and ablative 10,600 nm carbon dioxide fractional laser ( 3235 ) have been suggested as successful approaches for improving the appearance of sd . the present study was aimed at evaluating the effectiveness and safety of a novel non - ablative fractional 1565 nm device , which uses a dual impact technique  for targeting stretch marks , to achieve a demarcated dense impact together with a diffused deep impact within the same session . it was hypothesized that the treatment would improve both the aspects of texture and color of sd by elevating the atrophic base of the sd and simultaneously smoothing their ridges . this was a single - center research project conducted at the istituto dermatologico europeo in milan , italy . a total of 12 patients with variously - staged sd ( classified using the deprez - adatto scale , as i , iia , iib , iiia or iiib , and therefore not larger than 1 cm ) were recruited and treated between may and november 2013 . pregnant or breast feeding patients and patients who had been previously treated for sd with mechanical or laser therapy were excluded from the study . each patient received a total of three treatments , with a four to five - week interval between each treatment . one hour before each treatment , a very thin layer of an anesthetic cream containing 7% lidocaine and 7% tetracaine ( pliaglis , galderma ) was applied to the treatment area(s ) . after removal of the anesthetic cream , a careful disinfection of the area was performed with a non - colored benzalkonium chloride disinfectant . the device used for treating sd is a non - ablative fractional 1565 nm laser ( resurfx , lumenis ltd . , yokneam , israel ) . at each impact , the laser generates an array of focused microspots with a density adjustable by the operator and varying from 50 to 500 beams / cm . the practitioner can choose any of the six different shapes ( hexagon , circle , doughnut , square , rectangle , or line ) , and scan sizes ranging from 5 to 18 mm , with energy of up to 70 mj/spot . the device 's spot size is derived from the energy level chosen for the treatment . the reusable tip has an integrated contact cooling and a window through which the operator can visualize the aiming beam and therefore target the treatment area with high accuracy . we hypothesized that more microcolumns of denaturated dermis at the base of the sd will determine new collagen production , while a less dense deeper treatment of the ridges of the sd can flatten them . therefore , each treatment comprised two passes over the sd , each with a different setting as follows . each stria was first treated using a rectangular small spot size inside and in parallel to the long axis of the striae ( settings : 300 microspots / cm with 4044 mj / cm ) . the full area was then treated using a hexagonal shape large enough to impact inside and laterally to the margins of the striae ( settings : 150 microspots / cm and 5055 mj / cm ) . these treatment settings were repeated at each of the three treatment sessions . immediately after each treatment , a water - based emulsion containing triethanolamine ( biafine , johnson & johnson ) was applied to the treated area , and the patients were requested to apply a moisturizer multiple times each day , to maintain hydration of the skin . throughout the treatment course , all patients were required to avoid sun exposure and to use a broad - spectrum sunscreen of no less than 30 spf on a daily basis , replenishing it as often as needed . standard clinical images of the treated sd were acquired using the canon 5d mark ii camera ( canon inc . , tokyo , japan ) with an annular flash . to achieve high - quality  before and after  sets , the baseline images were taken under controlled conditions that included the distance , angle , background , and lighting . the volume of depressions and color ( melanin variation ) of each stria were analyzed using a 3d imaging system ( antera 3d - miravex , dublin , ireland ) . the system consists of a hand - held imaging device connected to a computer by a usb cable , and uses proprietary software . several light emitting diodes ( leds ) illuminate the skin with different colors and different illumination directions . the acquired image data are then used for spatial and spectral analysis for the reconstruction of skin texture , and for analysis of skin constituents . the acquired spectral images are transformed into skin spectral reflectance maps , and the shape of the skins surface is used to compensate for light intensity variation due to the varying directions of incident illumination . the reflectance data are transformed into skin absorption coefficients , and are used to quantify melanin and hemoglobin concentrations using mathematical correlation with known spectral absorption data of these chromophores . numeric data collected from one image must not be considered as absolute values , but when comparing two or more images , the percentage modification of these data is very useful to demonstrate eventual changes of the analyzed area . improvement of sd appearance was assessed by non - blinded and blinded reviewers , 3 months after the last treatment , using a percentage category scale ( no improvement  0% , slight improvement blinded reviews were performed by two plastic surgeons , who were not involved in any other part of the study , using clinical high - resolution pre- and post - treatment images . the treated patients were asked to give their own evaluation 3 months after the last treatment , using the percentage scale described above , and giving an overall judgment of satisfaction about the procedure using a 5-point scale ( no satisfaction , slight satisfaction , moderate satisfaction , good satisfaction , very good satisfaction ) . to obtain objective and quantitative data ( percentage ) on the improvement of the volume of depressions and color ( melanin variation ) of the sd in each patient , the pre- and post - treatment images were compared using the 3d imaging system software described above . patient assessment of pain and discomfort was evaluated using a 010 visual analog scale ( vas ) , where 0 represents  no pain  and 10 represents  intolerable pain  . immediate and short - term responses ( erythema , edema , purpura , etc . ) were assessed within 30 min post - treatment , according to a 4 level scale : 1 = trace ; 2 = moderate ; 3 = marked ; 4 = severe ( figures 1 and 2 ) . downtime was defined as the period of time following the procedure , during which the patient had edema and/or erythema and felt uncomfortable . erythema and edema are conspicuous . the skin of the patient in figure 1 , 30 min after the procedure . differences between results ( blinded and non - blinded reviewers ) were assessed using the independent t - test and the pearson correlation test . p - values of < 0.05 were considered statistically significant . a strong correlation was defined as r > 0.7 . this was a single - center research project conducted at the istituto dermatologico europeo in milan , italy . a total of 12 patients with variously - staged sd ( classified using the deprez - adatto scale , as i , iia , iib , iiia or iiib , and therefore not larger than 1 cm ) were recruited and treated between may and november 2013 . pregnant or breast feeding patients and patients who had been previously treated for sd with mechanical or laser therapy were excluded from the study . each patient received a total of three treatments , with a four to five - week interval between each treatment . one hour before each treatment , a very thin layer of an anesthetic cream containing 7% lidocaine and 7% tetracaine ( pliaglis , galderma ) was applied to the treatment area(s ) . after removal of the anesthetic cream , a careful disinfection of the area was performed with a non - colored benzalkonium chloride disinfectant . the device used for treating sd is a non - ablative fractional 1565 nm laser ( resurfx , lumenis ltd . , yokneam , israel ) . at each impact , the laser generates an array of focused microspots with a density adjustable by the operator and varying from 50 to 500 beams / cm . the practitioner can choose any of the six different shapes ( hexagon , circle , doughnut , square , rectangle , or line ) , and scan sizes ranging from 5 to 18 mm , with energy of up to 70 mj/spot . the device 's spot size is derived from the energy level chosen for the treatment . the reusable tip has an integrated contact cooling and a window through which the operator can visualize the aiming beam and therefore target the treatment area with high accuracy . we hypothesized that more microcolumns of denaturated dermis at the base of the sd will determine new collagen production , while a less dense deeper treatment of the ridges of the sd can flatten them . therefore , each treatment comprised two passes over the sd , each with a different setting as follows . each stria was first treated using a rectangular small spot size inside and in parallel to the long axis of the striae ( settings : 300 microspots / cm with 4044 mj / cm ) . the full area was then treated using a hexagonal shape large enough to impact inside and laterally to the margins of the striae ( settings : 150 microspots / cm and 5055 mj / cm ) . these treatment settings were repeated at each of the three treatment sessions . immediately after each treatment , a water - based emulsion containing triethanolamine ( biafine , johnson & johnson ) was applied to the treated area , and the patients were requested to apply a moisturizer multiple times each day , to maintain hydration of the skin . throughout the treatment course , all patients were required to avoid sun exposure and to use a broad - spectrum sunscreen of no less than 30 spf on a daily basis , replenishing it as often as needed . standard clinical images of the treated sd were acquired using the canon 5d mark ii camera ( canon inc . , tokyo , japan ) with an annular flash . to achieve high - quality  before and after  sets , the baseline images were taken under controlled conditions that included the distance , angle , background , and lighting . the volume of depressions and color ( melanin variation ) of each stria were analyzed using a 3d imaging system ( antera 3d - miravex , dublin , ireland ) . the system consists of a hand - held imaging device connected to a computer by a usb cable , and uses proprietary software . several light emitting diodes ( leds ) illuminate the skin with different colors and different illumination directions . the acquired image data are then used for spatial and spectral analysis for the reconstruction of skin texture , and for analysis of skin constituents . the acquired spectral images are transformed into skin spectral reflectance maps , and the shape of the skins surface is used to compensate for light intensity variation due to the varying directions of incident illumination . the reflectance data are transformed into skin absorption coefficients , and are used to quantify melanin and hemoglobin concentrations using mathematical correlation with known spectral absorption data of these chromophores . numeric data collected from one image must not be considered as absolute values , but when comparing two or more images , the percentage modification of these data is very useful to demonstrate eventual changes of the analyzed area . improvement of sd appearance was assessed by non - blinded and blinded reviewers , 3 months after the last treatment , using a percentage category scale ( no improvement  0% , slight improvement blinded reviews were performed by two plastic surgeons , who were not involved in any other part of the study , using clinical high - resolution pre- and post - treatment images . the treated patients were asked to give their own evaluation 3 months after the last treatment , using the percentage scale described above , and giving an overall judgment of satisfaction about the procedure using a 5-point scale ( no satisfaction , slight satisfaction , moderate satisfaction , good satisfaction , very good satisfaction ) . to obtain objective and quantitative data ( percentage ) on the improvement of the volume of depressions and color ( melanin variation ) of the sd in each patient , the pre- and post - treatment images were compared using the 3d imaging system software described above . patient assessment of pain and discomfort was evaluated using a 010 visual analog scale ( vas ) , where 0 represents  no pain  and 10 represents  intolerable pain  . immediate and short - term responses ( erythema , edema , purpura , etc . ) were assessed within 30 min post - treatment , according to a 4 level scale : 1 = trace ; 2 = moderate ; 3 = marked ; 4 = severe ( figures 1 and 2 ) . downtime was defined as the period of time following the procedure , during which the patient had edema and/or erythema and felt uncomfortable . erythema and edema are conspicuous . the skin of the patient in figure 1 , 30 min after the procedure . differences between results ( blinded and non - blinded reviewers ) were assessed using the independent t - test and the pearson correlation test . all patients were caucasians with skin type ii or iii , and their age ranged from 18 to 38 years ( mean 27 ) . the anatomic locations treated included the flanks , thighs , buttocks , breasts , abdomen , and shoulders ; the majority of treatments were performed at the first four sites . the time from sd onset ranged between 2 and 12 years ( mean , 8 years ) . the causes of sd were pubertal growth ( 4 patients , 33.3% ) , pregnancy ( 4 patients , 33.3% ) , weight change ( 3 patients , 25% ) , and unknown ( 1 patient , 8.3% , the male patient ) . all 12 patients completed the study ( and 7 of them asked to be treated in additional anatomic regions of their body ) . good clinical improvement ( between 51% and 75% ) was observed in all patients by the blinded as well as by the non - blinded reviewers ( figures 3 and 5 ) . the volume of sd depressions improved by more than 50% ( mean improvement 58% ) in the majority of patients ( 11/12 , 91.66% ) , and the color of the lesions improved by more than 50% ( mean improvement 54% ) in 83.33% of patients ( 10/12 ) ( figures 9 , 4 and 6 ) . the average pain during treatment was generally defined as tolerable ( mean 23 out of a 10-point scale ) , and the average downtime was 4 days . marked erythema and severe edema were noted immediately after the procedure ; however , 30 min after the procedure , the edema decreased to trace . all patients noted a good improvement and were satisfied with the treatment and with the results during the follow - up period as well . one patient was only moderately satisfied , more due to the length of the procedure , rather than due to the results themselves ( figure 10 ) . no long - lasting or severe adverse effects were observed ; a single patient presented a prolonged ( 7 days ) micro - crusting effect on the treated area ( figure 7 ) that shed off with no sequela within a week . the percentage improvements provided by the blinded and non - blinded reviewers were not statistically significantly different between these two groups of reviewers ( p = 0.06 , by the t - test ) and were strongly correlated ( r = 0.763 ) . a strong correlation was also observed between the results of the blinded reviewers and those of the 3d analysis ( r = 0.709 ) , as well as between the results of the non - blinded reviewers and those of the 3d analysis ( r = 0.731 ) , indicating low inter - observer variations . a 28 year - old , st iii female who presented widespread striae alba from pregnancy ( an onset of 3 years ) . the top image was taken before treatment , and the bottom image was taken after 3 treatment sessions , as described in the section , materials and methods . marked improvements in the texture as well as the color of the striae ( from iiib to iia , according to the deprez - adatto scale ) can be seen following the treatment , as compared to the baseline . the 3d skin surface analysis of the 28 year - old , st iii female depicted in figure 3 , before the treatment ( left ) , and 3 months after the end of treatment ( right ) . a 22 year - old st iiib female who presented with widespread striae alba after weight loss . the image on the left was taken before treatment and the image on the right was taken after 3 treatment sessions , as described in the section , materials and methods . marked improvements in the texture as well as the color of the striae ( from iiib to iia , according to the deprez - adatto scale ) can be seen following the treatment , as compared to the baseline . the 3d skin surface analysis of the 22 year - old , st iii female depicted in figure 5 , before the treatment ( left ) and 3 months after the end of treatment ( right ) . micro - crusting of the skin , observed 6 days after the procedure in a 31 year - old female patient . evaluation of the improvement in striae 3 months after the last treatment session , by investigators and patients . numerous therapeutic strategies for sd have been suggested to date , but no consistent treatment modality has been established yet ( 2,3,920 ) . from the numerous modalities used to improve sd , lasers have recently become a popular therapeutic alternative . specifically , fractional photothermolysis looks promising in dermal remodeling and subsequent improvement of white and pigmented sd , as well as in effectively treating different kinds of scars ( 2735,3839 ) . preliminary investigations of fractional non - ablative photothermolysis demonstrated the capability of this technology to induce dermal remodeling ( 4042 ) , and these histologic changes ( neocollagenesis , increased epidermal thickness ) have recently been confirmed in striae studies with the 1550-nm laser ( 27,29 ) . to the best of our knowledge , the present study was the first to evaluate the effectiveness of a non - ablative fractional 1565 nm device on mature sd . two laser settings were used for treating each stria ( dual impact technique ) ; the first setting was intended to achieve a demarcated dense impact because the base of an atrophic scar needs greater collagen production to elevate it , and the second setting was intended to achieve a diffused deep impact in order to smooth the ridges of the scar , in order to reduce the shadow produced by incident light . indeed , the volume of depressions and the color of the lesions were both improved by more than 50% in over 80% of the patients following treatment . erythema and edema were expected in this type of treatment , but subsided shortly after treatment . both ablative and non - ablative fractional treatments have shown promising results for treating sd , but controlled studies are scarce . in a study comparing the effect of ablative co2 fractional laser with that of non - ablative 1,550 nm erbium ( er ) : glass fractional laser on sd in asian patients , both modalities showed similar improvements of sd ; however treatment with the ablative co2 fractional laser was considered more painful than the treatment with the non - ablative fractional laser , and resulted in more post - inflammatory hyperpigmentation and longer post - treatment erythema ( 34 ) . within non - ablative devices , ( 27 ) reported a mean clinical improvement of 25% to 50% with a 1550 nm laser , the majority graded the improvement no greater than 25% . of the eight patients randomly evaluated in a study with the 1550 nm laser by stotland et al . ( 35 ) , 63% of the patients demonstrated improvements of 26% to 50% . on the other hand , de angelis et al . these studies also demonstrated a thickening of the epidermis and dermis , as well as an increased number of collagen fibers at 30 days after the last treatment . additionally , they observed an increased number and more uniform distribution of elastic fibers in the papillary dermis . the limitation of the present study includes the lack of histologic assessment , a limited number of patients , the absence of dark - skinned patients , and the lack of a longer follow - up period ; however the study presents , for the first time , an objective evaluation of the improvement of sd after treatment with this modality . in conclusion , the current study demonstrated a significant improvement in texture , volume , and color of white sd , with minimal adverse effects . these results were supported by the correlation between the blinded and the non - blinded evaluation of improvement after treatment , as well as by the correlation between the reviewers and the 3d analysis . the procedures were extremely well - tolerated by the patients , and the results were so convincing that 58% of them asked to be treated in another anatomic region of their body . the risk of eventual associated hyperpigmentation should never be underestimated , and therefore , additional studies are required . in general , sd remain a challenge ; they are difficult to treat , and patients expectations are always very high . for these reasons , we are still persuaded that any therapy and associated side effects should be critically discussed with the patient before therapy .
abstract 
 background : striae distensae ( sd ) is a very common dermatologic condition . 
 we evaluated the effectiveness and safety of a novel non - ablative fractional 1565 nm laser ( resurfx ) on the appearance of sd . 
 materials and methods : twelve caucasian subjects with various stages of sd received three non - ablative laser treatments . 
 each treatment consisted of two different laser settings , in order to achieve a demarcated dense impact together with a diffused deep impact . 
 three months after the last treatment , sd improvement was assessed by blinded and non - blinded reviewers using clinical images and 3d image analyses . 
 results : good clinical improvement ( between 51% and 75% ) was observed in all patients . 
 most patients showed improvement of > 50% in the volume of depressions and in lesion color ( 91.7% and 83.3% of patients , respectively ) . 
 the average pain during treatment was generally defined as tolerable and the average downtime was 4 days . 
 transient erythema and severe edema were noted immediately after the procedure , but long - lasting or severe adverse effects were not observed . 
 all patients noted a good improvement and were satisfied with the treatment and the results . 
 conclusions : the treatment with the 1565 nm resurfx laser resulted in improved pigmentation , volume , and textural appearance of sd .