solar lentigines are well - circumscribed or irregularly shaped dark brown or black macules that occur on sun - exposed areas , predominantly on dorsal aspects of the hands and the face . because of the negative social impact on quality of life ,
there are two types of treatment : ( 1 ) physical therapies , which include cryotherapy , laser therapy , intense pulsed light ( ipl ) , and chemical peeling and ; ( 2 ) topical therapies such as hydroquinone and tretinoin .
although it is inexpensive and effective , side effects such as post - inflammatory hyperpigmentation ( pih ) limit its use especially in darker fitzpatrick 's skin types . because of the broad absorption spectrum of melanin ( 351 - 1064 nm ) , multiple type of lasers ( e.g. , pulsed dye laser ( pdl ) , q - switched ruby , q - switched nd : yag ) have been used in the treatment of solar lentigines .
although pdl is a gold standard laser treatment for many superficial cutaneous vascular lesions , several studies suggest the good efficacy of pdl with compression in the treatment of solar lentigines.[410 ] to our knowledge , there are no published studies comparing cryotherapy with 595-nm pulsed dye laser ( pdl ) and cutaneous compression in the treatment of solar lentigines .
the aim of this study was to compare the efficacy and safety of these modalities in the treatment of solar lentigines .
twenty - four patients with fitzpatrick 's skin type ii - iv with facial or hand lentigines were enrolled in this evaluator - blinded randomized clinical trial .
all patients , who completed follow up , were between the ages of 28 and 67 years ( mean , 51.2 years ; 20 females and 2 males ) and had solar lentigines on their face or hands based on clinical diagnosis .
the exclusion criteria were as follows : pregnancy , recent sun tanning , previous laser or topical treatments , history of oral retinoid treatment with in the previous 6 months , known photosensitivity or taking photosensitizing medication and history of vitiligo or psoriasis or keloid formation .
the study protocol conformed to the ethical guidelines of the 1975 declaration of helsinki , and was confirmed by the ethical committee of our university .
lesions of one side of the face or each hand were randomly assigned and treated with either cryotherapy or 595-nm pdl ( vbeam , candela corporation , wayland , ma ) with cutaneous compression .
treatments were performed with radiant exposures of 10 j / cm , 7-mm spot size , and 1.5-ms pulse duration with no epidermal cooling . during each pulse , proper compression with convex surface of a fused - silica meniscus optical element with zero optical power was used to push the blood to the outside of laser treatment area and prevent purpura .
the cryospray was applied for 35 s on each lesion from a distance of 3 cm from the lesion .
patients were asked to avoid sun exposure and use sunscreen on their hands and face . before treatment and 1-month later , digital photographs were taken with the same camera .
two blind observers ( both board - certified dermatologists ) were asked to grade each treated site ( hands or face ) according to  before  and  after  pictures .
the degrees of lightening of the lentigines were graded as either poor ( minimal change with lightening of 0%25% ) , mild ( slight improvement with lightening of 26%50% ) , moderate ( though quite improved , can be differentiated from the surrounding healthy skin with lightening of 51%75% ) , or marked ( difficult to differentiate from the surrounding healthy skin with lightening of 76%100% ) .
the side effects including pih and hypopigmentation , post - pdl erythema , atrophic and hypertrophic scar were recorded in a follow - up session after 1 month .
data were analyzed with spss 16.0 software using wilcoxon - signed - ranks test and chi - square test .
of the original 24 patients , 22 patients ( 20 females and 2 males ) participated in this study .
the frequency of fitzpatrick 's skin types were as follows : five cases ( 22.7% ) skin type ii , eight cases ( 36.4 % ) skin type iii and nine cases ( 40.9 % ) skin type iv .
about two - thirds ( 68.2% ) of the lentigines were on the dorsum of the hands and 31.8% on the face .
after 1 month , pdl with compression produced more than 75% lightening ( marked improvement ) in 10 patients ( 45.5% ) compared with 2 patients ( 9.1% ) in the cryotherapy group [ table 1 ] .
statistical analysis showed a significant difference ( p < 0.05 ; [ figures 1 and 2 ] , respectively ) .
response to treatment in study groups treatment response after treatment : marked improvement of medial lesion with pdl with compression after 1 month pdl response showed a significant difference in patients with fitzpatrick 's skin type iii and iv ( n = 8 , n = 9 ; p < 0.05 ) .
in contrast , there might be no significant difference between pdl and cryotherapy response in fitzpatrick 's skin type ii ( n = 5 ; p > 0.05 ) [ table 2 ] .
side effects were only post - pdl minimal erythema ( after 1 month ) in six patients ( 27.3% ) of the pdl group and only ( pih ) in eight patients ( 36.4% ) of the cryotherapy group .
there were no other side effects such as atrophic and hypertrophic scar or purpura or hypopigmentation .
topical therapies of solar lentigines have fewer side effects but usually take longer than physical therapies to achieve a good result .
these are frequently used with excellent clinical success rate ; however , these types of therapies should be balanced against associated side effects .
cryotherapy is one of the most widely used and effective treatments in this field which is inexpensive and easily accessible .
the principle of treatment in cryotherapy in solar lentigines is melanocytes vulnerability to cold injury , which can destroy them at temperatures of 4c to 7c .
accordingly , various types of lasers such as pulsed dye ( 595 nm),[410 ] frequency - doubled nd : yag ( 532 nm ) , ktp ( 532 nm ) , q - switched ruby ( 694 nm ) , q - switched and long - pulse alexandrite ( 755 nm ) , and q - switched nd : yag ( 1064 nm ) have been used to treat solar lentigines .
recently , this laser has been usedsuccessfully for the treatment of epidermal pigmented lesions such as solar lentigines , freckles , and seborrheic keratosis with some modifications .
using skin compression during pdl removes the blood from the targeted treatment area , effectively eliminating hemoglobin as a competing target chromophore , and thereby minimizing the risk of purpura production , and allowing for the use of effective radiant exposure range for treating epidermal pigmented lesions ( 910 j / cm , 1.5-ms pulse duration).[45 ] epidermal cooling , which is usually used during treatment of vascular lesions with pdl , decreases the interaction between laser energy and the superficial pigmented lesion . similar to previous studies,[410 ] epidermal cooling was not used in our study and no epidermal burning was recorded .
kono et al . attached a flat glass to the laser 's hand - piece in their first study .
later they found that attaching a convex glass instead of flat one allows for a more uniform blood displacement during skin compression from the irradiated field and better preventing purpura .
used convex surface of a fused - silica meniscus optical element with zero - optical power for compressing the skin during laser treatment . by using this compression technique ,
darker skin patients such as asians have higher epidermal melanin content and are more likely to develop erythema and pih , which can be considered as a default pathophysiologic response to cutaneous injury in these patients .
several factors contribute to the development of pih , including increased melanocytic activities , dermal melanophages , and hemosiderin deposition secondary to hemorrhage .
the severity of pih is related to the degree of inflammation and extent of disruption of the dermo - epidermal junction caused by endogenous inflammatory skin disorders or iatrogenic sources such as lasers and cryotherapy .
we have pih in our patients only in cryotherapy group suggesting that inflammatory response which is responsible for developing pih may be more prominent in cryotherapy than pdl group . although q - switched ruby and alexandrite are highly effective in the treatment of lentigines , the risk of complications such as erythema , blistering and pih in darker skin types ( fitzpatrick 's skin type iii and iv ) in these lasers are higher .
kono et al . compared q - switched ruby laser ( qsrl ) versus pdl with compression for treating facial lentigines in asian ( fitzpatrick 's skin type iii and iv ) .
they found that pdl with compression is more effective than qsrl with substantially less side effects .
this study showed that pdl with compression is superior to qsrl for treating pigmented lesions in darker fitzpatrick 's skin types . in our study , no pih was seen in the pdl group .
todd et al . compared three type of lasers ( frequency - doubled q - switched nd : yag laser , krypton laser , and 532-nm diode - pumped vanadate laser ) , and cryotherapy in the treatment of solar lentigines .
it is difficult to directly compare these results with our study , as the types of the lasers used , are different .
however , similar to todd study , the improvement in our patients in laser group wassuperior to cryotherapy ( p < 0.05 ) with fewer side effects .
compared cryotherapy versus trichloroacetic acid 33% ( tca ) in solar lentigines treatment and found better results with cryotherapy .
pih was the major complication in both treatments especially in fitzpatrick 's skin type iii and iv . in our study , we detected pih only in cryotherapy group especially in darker skin types .
our study is a pilot one to compare efficacy and safety of a popular therapeutic modality like cryotherapy with a new laser method , pdl 595-nm with compression , in the treatment of solar lentigines .
therefore , it seems that confirming these results needs more studies with larger population size .
finally , it seems that the major factor in determining the therapeutic modality for solar lentigines is fitzpatrick 's skin type . in darker skin types such as skin type iii and iv
however , when the patient has lower skin types such as skin type ii , there may be no difference between the two therapeutic methods .
in addition , side effects in pdl with compression are minimal ( only minimal erythema in a few cases without pih or purpura ) as compared with cryotherapy .
 background : although cryotherapy is still the first - line therapy for solar lentigines , because of the side effects such as post - inflammatory hyperpigmentation ( pih ) , especially in patients with darker skin types , pigment - specific lasers should be considered as a therapy for initial treatment.aim:the aim of this study is to evaluate the efficacy and safety of cryotherapy compared with 595-nm pulsed dye laser ( pdl ) with cutaneous compression in the treatment of solar lentigines.materials and methods : twenty - two patients ( skin type ii  
 iv ) with facial or hand lentigines participated in this study . 
 lesions of one side of the face or each hand were randomly assigned and treated with either cryotherapy or pdl . 
 treatments were performed with radiant exposures of 10 j / cm2 , 7-mm spot size and 1.5 ms pulse duration with no epidermal cooling . 
 photographs were taken before treatment and 1-month later . 
 the response rate and side effects were compared.results:pdl was more likely to produce substantial lightening of the solar lentigines than cryotherapy , especially in skin type iii and iv ( n = 8 , n = 9 ; p < 0.05 ) , but might be no difference in type ii ( n = 5 ; p > 0.05 ) . 
 pih was seen only in cryotherapy group . 
 pdl group had only minimal erythema . 
 no purpura was observed.conclusion:pdl with compression is superior to cryotherapy in the treatment of solar lentigines in darker skin types . 