atrophic scars can result from any inflammatory skin disease causing sufficient damage to the epidermis and to the dermal collagen . the most common causes of atrophic scars especially on the face are severe nodular or nodulocystic acne , infections like varicella and herpes simplex , trauma including burns and lastly , surgical procedures . facial scars resulting from any of these etiologies are associated with psychological trauma and loss of self esteem . successful treatment of these scars can be a satisfying experience to the patient and the treating physician . facial scars resulting from acne are either hypertrophic or atrophic depending upon whether they are elevated or depressed in relation to the skin surface . the atrophic facial scars are divided into different morphological types depending on the shape and depth of the scars . the four main morphological types of atrophic post acne scars are icepick pitted scars , superficial or deep boxcar scars , rolling scars and linear scars . treatment of each morphological scar type varies and while one scar type responds the best to some treatment modality , the same treatment option may not be necessarily effective in other type of scars . facial resurfacing with fractional lasers is currently claimed to be one of the most effective treatment options for facial scars . fractional lasers treat only a  fraction or a column of the affected skin leaving intervening areas of skin untreated . these untreated areas help in rapid re - epithelisation of the skin , minimising the chances of prolonged and serious adverse effects . while the former are claimed to be the safer of the two types , the latter have been shown to be more effective in treating facial imperfections with better patient satisfaction . fractional co2 laser resurfacing has been used in the treatment of atrophic scars with varying degrees of success . adverse effects in the form of persistent post - treatment erythema , crusting , post - inflammatory hyper pigmentation , purpura and even aggravation of scarring have been described as adverse reactions to this treatment option . for fractional laser resurfacing to be effective , it is important to realise that the depth shows a non - linear correlation with the density and energy settings that are used with an individual laser . for the present study we used a fractional co2 laser qray - frx from dosis , korea marketed by coherent india ltd . the machine has two separate hand - pieces for fractional co2 laser and non - ablative radio - frequency with infrared non - ablative laser combination . for treating acne scars , sixty patients of moderate to severe atrophic facial acne scars were treated with fractional co2 laser resurfacing monotherapy over a period of three years from february 2010 to january 2013 . exclusion criteria included keloidal tendency , pregnancy , active acne , immunosuppression and concomitant isotretinoin use . patients who were using any topical treatments for acne or for scars were told to stop these medications at least 1-week before the start of fractional laser treatment . no concomitant cosmetic procedures were allowed between the laser sessions and no topical drugs were prescribed except sunscreens and topical antibiotic creams in the post - procedure period . after an informed consent was taken , a baseline photograph showing all the scars to be treated was taken using standard camera angle and light settings . then , a topical anaesthetic cream containing a eutectic mixture of topical tetracaine and lignocaine in a cream base ( tetralid cream ) was applied for 1 hour on the treatment area to achieve a satisfactory anaesthetic effect . after satisfactory anaesthesia was achieved , the treatment area was cleaned with a mild cleanser followed by 70% ethanol solution . fluence ranging from 15 - 25 j / cm was used at densities of 100 - 150 mtz / cm , thus providing about 40 - 45mj of energy and an ablation depth of 1.0 - 1.2 mm at each spot . each morphological type of scar was treated in a similar manner and the patient was advised skin cooling with ice - packs for 5 - 10 minutes after the procedure to take care of post - treatment erythema , oedema and burning sensation . the patients were instructed to prevent sun exposure for the next 4 - 5 days after each procedure and a topical non - occlusive antibiotic cream formulation was prescribed over this period . the patients were also encouraged to use a broad - spectrum sunscreen liberally in between the laser sessions . oral acyclovir was prescribed only to those patients who had a history of recurrent herpes simplex infections . laser procedure was repeated every 6 weeks and a total of 3 - 4 sessions were performed in each patient . the laser parameters were kept identical at each visit and if the patient was satisfied with the results obtained after the 3 session , the 4 session was not performed . digital photographs were taken using identical lighting , angle and face position settings at every follow up visit . the final assessment was made subjectively by a single observer at the last follow - up visit , 6 months after the last laser session and a quartile grading scale was used to assess the response objectively . a score of 0 , 1 , 2 and 3 was thus given if the response was < 25% , 25 - 50% , 51 - 75% and > 75% , respectively . the response was termed as excellent if the score was 2 or more and good if the score obtained was 1 . in addition to the photographic and clinical assessment , the patient 's satisfaction to the treatment was also recorded at the final visit . adverse effects , if any , were also monitored at each follow - up visit . there were 25 males and 35 females in the study group and majority of them ( 38 patients ) were in the 3 decade of life . there were 3 patients with fitzpatrick skin type 2 , 39 patients with skin type 3 and 18 patients with skin type 4 . demographic data of patients all the cases had moderate to severe atrophic post - acne scars ( grade 3 and 4 scars by goodman and baron classification system ) . in majority of cases ( 35 out of 60 ) , the commonest sites involved were the cheeks followed by temples and forehead . at the 6-month follow - up visit after the last laser session , a positive response with either good or excellent results was documented in 41 patients corresponding to 68.3% of the study group . of these 41 responders , there were 11 patients ( 18.3% ) in whom > 75% improvement was seen in scars and skin texture [ figure 1 ] while in 15 others , the improvement was in the range of 51 - 75% . thus , excellent response ( score 2 or more on quartile grading scale ) was observed in a total of 26 patients ( 43.3% ) . fifteen patients ( 25% ) showed a good response while 19 patients ( 31.7% ) failed to demonstrate any significant response to treatment with < 25% improvement on the quartile scale [ table 2 ] . ( a ) acne scars in early stage , ( b ) excellent response , seen 6 months after the 4 laser session response to treatment shown by different morphological types of scars patient satisfaction survey revealed that about 73% ( 44 cases out of the total of 60 ) were satisfied with the treatment results . for the remaining 16 cases , the improvement achieved was not up to their expectations . in general , rolling scars were seen to respond the best to fractional laser resurfacing monotherapy [ figure 2 ] while icepick pitted scars responded the least . in fact , almost all of the rolling scars showed excellent response to treatment and all the 11 patients who showed > 75% improvement in scars had predominantly rolling type of scars [ table 2 ] . on the other hand , patients who achieved the minimum improvement score had predominantly ice - pick scars or deep boxcar scars on their face [ figure 3 ] . ( a ) predominantly rolling scars ( b ) excellent response after 3 sessions of fractional co2 laser resurfacing ( a ) predominantly boxcar scarring ( b ) partial response to fractional laser resurfacing adverse effects to the treatment regimen were usually transient and included erythema that usually lasted for an average of 3 - 4 days , superficial crusting lasting for 4 - 6 days and mild transient edema . transient acneiform lesions were seen in 6 patients and in 2 of these , oral treatment was necessitated . the only significant adverse effect observed was post - inflammatory hyperpigmentation that developed in 3 cases in our study . it is always a challenge to treat a patient with moderate to severe acne scars . there are morphologically different types of scars and the individual depth of these scars also varies in between patients and even in a single patient . all these factors make the assessment of efficacy of any therapeutic option difficult to judge across all the patients . laser resurfacing with co2 laser or er : yag laser gives excellent results when used in the treatment of aging skin and acne scars . however , the risks associated with the procedure including the chances of prolonged erythema lasting for weeks to months , oozing and crusting and post - inflammatory pigmentation especially in darker skin limit the usefulness of this therapeutic option . fraction of the whole skin is treated and the integrity of epidermis is not compromised . as each microscopic wound created by the laser device is surrounded by normal , healthy tissue , the healing is rapid and the adverse effects are reduced to a considerable degree . a number of clinical studies have documented a positive therapeutic effect of ablative fractional laser resurfacing with either er : yag or co2 laser . alster et al . , in a study on 53 patients documented a clinical improvement in the range of 51 - 75% in about 90% of their patients with fractional erbium - doped fibre laser . fractional co2 laser , with a wavelength of 10,600 nm , has also been employed in the treatment of acne scars in both caucasian as well as asian patients . chapas et al . , in their study on facial acne scars , documented improvement of 26 - 50% in texture and atrophy of the skin in all patients . the investigators also used an imaging system ( primos ) to analyse the change in the topography of scars . this imaging system also documented an objective improvement in the depth of individual scars ranging from 43% to 79.9% with a mean improvement of 66.8% . the adverse effects seen in the patients were again self - resolving and none of the enrolled patients developed any long - term or permanent adverse effects . in a single - blinded randomised study on acne scars , hedelund et al . demonstrated statistically significant improvement in skin texture and atrophy in comparison with placebo after 3 monthly laser sessions with fractional co2 device . the study was conducted on 13 patients and the patients were also quoted as being satisfied with the treatment option . relatively higher energies in the range of 48 - 56mj with a treatment density of 13% were used in this study . in asian patients , sung bin cho and co - workers demonstrated the efficacy as well as safety of fractional co2 laser resurfacing in acne scars . half of the 20 patients enrolled in this study achieved clinical improvement of > 50% while another 7 patients achieved 26 - 50% improvement . the mean post - treatment erythema and crusting lasted for 2.8  4.6 days and 6.3  3.0 days , respectively . in our study , we used energy in the range of 12 - 20j / cm and treatment density of 150 - 200 mtz / cm in all patients . these treatment parameters were decided on the basis of the skin type of our patients as most of them had fitzpatrick skin type 3 or 4 . we treated all individual scars with the same laser fluence and treatment density irrespective of their depth or morphological type . good to excellent response was achieved in about 67% patients on the quartile grading scale . this figure is in conformity with the figures quoted in most of the studies on co2 fractional laser resurfacing in acne scars . while about 40% patients achieved > 50% improvement , additional 27% patients were seen to have 25 - 50% improvement in scar morphology and texture in the study group . subjectively also , majority of the patients were satisfied with the results obtained after the end of treatment schedule . adverse effects seen were not significant and none of the enrolled patients had any long - term or permanent side effects from the procedure . however , there is certainly some down - time associated with fractional co2 laser resurfacing as patients do experience crusting for a few days after the procedure . this crusting makes it impossible for patients to resume their normal work for a few days after each laser session . a nice way to circumvent this problem is to perform the procedure just before a weekend so that the patients get a rest of 2 days and no professional commitments are missed after the laser sessions . additionally , post - inflammatory hyper pigmentation was observed in 3 patients in our series which resolved with topical treatments over a span of 6 - 12 weeks . this warrants the use of broad spectrum sunscreens and limitation of sun exposure after the laser sessions are performed . of all the scar types , rolling scars were seen to respond the best while icepick pitted scars responded the least to treatment in the study population . this observation carries a lot of therapeutic importance as simple fractional laser resurfacing monotherapy is unlikely to take care of pitted scars . thus , if pits or ice - pick scars are the predominant scar type in any individual patient , the patient is unlikely to be satisfied with fractional laser resurfacing monotherapy alone . such a patient would need either supplementary treatment with tca cross ( chemical reconstruction of scars by 80 - 100% trichloracetic acid ) technique or surgical techniques like punch excision or punch floatation if practically feasible . while commenting on the therapeutic results achieved with fractional laser resurfacing , it is important to realise that there is a lack of uniform objective assessment of the therapeutic benefit achieved . majority of the clinical studies on fractional laser technology have used quartile grading systems or patient satisfaction as the criteria to assess the therapeutic results . both of these criteria are fraught with subjective bias and there is an urgent need for a proper objective tool that can be used across the whole spectrum of post acne scars to assess any therapeutic benefit . another important fact is that there are just a few studies that have commented upon the therapeutic results in different morphological types of acne scars . all other studies have made a generalised or a sweeping statement on the results obtained without taking into account the differences in the response between the morphological scar types . lastly , it is important to realise that a typical patient has scars of different morphological types and grades and it is difficult to treat all these scar types satisfactorily with a single treatment option and multiple techniques are required . however , of all the treatment options available to treat post - acne scars , fractional photothermolysis is probably the only monotherapy that offers the highest degree of scar amelioration and patient satisfaction .
background : while laser resurfacing remains the most effective treatment option for atrophic acne scars , the high incidence of post - treatment adverse effects limits its use . 
 fractional laser photothermolysis attempts to overcome these limitations of laser resurfacing by creating microscopic zones of injury to the dermis with skip areas in between.aim:the aim of the present study is to assess the efficacy and safety of fractional co2 laser resurfacing in atrophic facial acne scars.materials and methods : sixty patients with moderate to severe atrophic facial acne scars were treated with 3 - 4 sessions of fractional co2 laser resurfacing at 6-week intervals . 
 the therapeutic response to treatment was assessed at each follow up visit and then finally 6 months after the last laser session using a quartile grading scale . 
 response to treatment was labelled as 
 excellent if there was > 50% improvement in scar appearance and texture of skin on the grading scale while 25 - 50% response and < 25% improvement were labelled as 
 good and  poor response , respectively . 
 the overall satisfaction of the patients and any adverse reactions to the treatment were also noted.results:most of the patients showed a combination of different morphological types of acne scars . at the time of final assessment 
 6 months after the last laser session , an excellent response was observed in 26 patients ( 43.3% ) while 15 ( 25% ) and 19 patients ( 31.7% ) demonstrated a good and poor response respectively . rolling and superficial boxcar scars responded the best while pitted scars responded the least to fractional laser monotherapy . 
 the commonest reported adverse effect was transient erythema and crusting lasting for an average of 3 - 4 and 4 - 6 days , respectively while three patients developed post - inflammatory pigmentation lasting for 8 - 12 weeks.conclusions:fractional laser resurfacing as monotherapy is effective in treating acne scars especially rolling and superficial boxcar scars with minimal adverse effects .