corneal fibroblast culture and cell viability test for onion extract : 
 corneal fibroblasts were cultured from porcine eyes , which were obtained from a local 
 slaughterhouse , for the cell viability test of the onion extract . the corneal buttons 
 removed by an 8-mm diameter trephine ( barron radial vacuum trephine , katena products , inc . , 
 denvile , nj , u.s.a . ) were obtained . after then , the epithelial cells of the corneal buttons 
 were scrapped off using a # 10 scalpel blade , descemet s membranes were peeled off , and the 
 corneal stromas were washed with phosphate buffered saline ( pbs , ph 7.4 ) ( 10010 - 023 , 
 gibco , grand island , ny , u.s.a . ) . the corneal buttons were cut into four 
 small pieces and incubated overnight in a humidified co2 incubator at 37c in 
 dulbecco s modified eagle s medium ( dmem ) ( 11995 - 065 , gibco ) containing 20 mm 
 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid ( hepes , 15630 - 080 , gibco ) 
 and 1.25 mg / ml collagenase type i ( 17100 - 017 , gibco ) . the 
 digested tissues were mixed with media by pipetting and filtered a 100 m 
 cell strainer ( 08 - 771 - 19 , falcon , franklin lakes , nj , u.s.a . ) . then , they were 
 centrifuged at 800 g for 5 min and resuspended in 2 ml of dmem containing 
 20 mm hepes , 50 g / ml gentamicin ( 15750 - 078 , 
 gibco ) , 1.25 g / ml amphotericin b ( a20678 , 
 gibco ) and 10% fetal bovine serum ( 10437 - 028 , gibco ) . this 
 keratocyte - containing cell suspension was then seeded on 6-well plastic dishes and incubated 
 in a humidified co2 incubator at 37c . eighty percent confluent cultures of 
 cornea fibroblasts ( passages 13 ) were used for experiments . trypan blue dye exclusion test was used to evaluate cell viability of corneal fibroblasts 
 after treating onion extract . louis , mo , u.s.a . ) 
 was treated to the each well at 0 , 0.01 , 0.1 , 1 , 10 , 50 and 100 
 l / ml concentrations diluted with dmso ( amr-0231 - 1 ; 
 amresco , solon , oh , u.s.a . ) for 24 hr . then , they were resuspended using 0.05% trypsin/0.53 
 mm edta ( 25300 - 054 , gibco ) , and trypan blue solutions ( 0.4% wt / vol , 15250 - 061 , 
 gibco ) were mixed with the resuspension cells . a process of manufacture for the onion extract ointment : a 1% onion 
 extract ointment was made with 10 g white petrolatum ( white petrolatum 1 g / g , sungkwang 
 pharm . , cheonan , korea ) and 0.1 ml onion extract ( w281719 , sigma - aldrich ) 
 mixture in a water bath . the concentration of onion extract ointment depended on the 
 in vitro viability test . before use in a main study , the onion extract 
 ointment was applied bid for 2 weeks at the normal cornea of six healthy beagle dogs to test 
 the abnormal allergic reactions ( blepharospasm , conjunctival hyperemia , corneal epithelial 
 disorders and other ocular abnormality ) by ophthalmic examinations every the other days . animals : twenty - four eyes from 12 healthy beagles were used in this study . 
 before the experiment , all dogs underwent an ophthalmic examination including slit - lamp 
 biomicroscopy ( sl - d7 , topcon , tokyo , japan ) , indirect ophthalmoscopy ( vantage plus , keeler , 
 windsor , u.k . ) , rebound tonometry ( tonovet , tiolat , helsinki , finland ) , schirmer s tear test 
 ( schirmer tear test , intervet , summit , nj , u.s.a . ) and fluorescein staining ( fluorescein 
 paper , haag streit ag , koeniz , switzerland ) . dogs with ocular or systemic diseases were 
 excluded . the animal use and experimental protocols were approved by the institutional 
 animal care and use committee ( snu-121123 - 10 ; seoul national university , korea ) . all dogs 
 were divided into 4 groups consisting of 6 eyes in each group ; control ( group c ; n=6 ) , 
 prednisolone acetate treatment ( group p ; n=6 ) , onion extract treatment ( group o ; n=6 ) and 
 tgf-1 treatment ( group t ; n=6 ) . corneal haze generation by the air assisted lamellar keratectomy : air 
 assisted lamellar keratectomy was performed following a method reported previously . general anesthesia was accomplished by intravenous 
 injection of tiletamine and zolazepam ( zoletil , virbac , carros , france ; 2.5 mg / kg ) for 
 induction and maintained with isoflurane ( ifran , hana pharm , seoul , korea ; mac 0.51.5% ) . atracurium ( atra , hana pharm ; 0.01 mg / kg , iv ) was administrated for central positioning of 
 the cornea during the surgery . briefly , the center of the cornea was trephined 375 m using an 8 mm 
 diameter trephine ( barron radial vacuum trephine , katena ) ( fig . ( a ) the center of the cornea was trephined 375 
 m using an 8 mm vacuum trephine . ( b ) four ml of 
 air was injected at the base of the trephination gutter into the corneal stroma using 
 a 30-gauge needle attached to a syringe . ( c ) intrastromal blanching was observed , and 
 the blanched cornea was removed using a corneal dissector and blunt - tipped corneal 
 scissors . ( d ) appearance after keratectomy using the air assisted lamellar 
 keratectomy . ) . four ml of air were injected at the base of the trephination gutter into 
 the corneal stroma using a 30-gauge needle attached to a syringe . the needle was bent 5 mm 
 from its tip so that the terminal segment angled upwards approximately 60 , while the bevel 
 faces up ( fig . the tip was introduced 
 parallel to the corneal surface into the central stroma at the base of the trephination 
 groove . the plunger of the air - filled syringe was pressed until intrastromal blanching was 
 observed ( fig . the fuzzy region of the white 
 opaque cornea was removed using a corneal dissector and blunt - tipped corneal scissors ( fig . ( a ) the center of the cornea was trephined 375 
 m using an 8 mm vacuum trephine . ( b ) four ml of 
 air was injected at the base of the trephination gutter into the corneal stroma using 
 a 30-gauge needle attached to a syringe . ( c ) intrastromal blanching was observed , and 
 the blanched cornea was removed using a corneal dissector and blunt - tipped corneal 
 scissors . after surgery , one drop of atropine ( 1% , isopto atropine , alcon , antwerp , belgium ) was 
 applied for 3 days for the purpose of analgesic effect . levofloxacine ( 0.5% , cravit , santen , 
 osaka , japan ) eye drops were administered three times daily until 7 days after the surgery . after the seventh day , artificial tear eye drops ( 0.1% sodium hyaluronate ; lacure , samil 
 pharm . , seoul , korea ) for group c , prednisolone acetate 1% ( pred - forte , allergan , irvine , 
 ca , u.s.a . ) for group p , an onion extract ( w281719 , sigma - aldrich , st . louis , mo , u.s.a . ) 
 ointment 10 ml / mg diluted with a white petrolatum ( vaseline , sungkwang 
 pharm , cheonan , korea ) for group o and tgf-1 ( t7039 , sigma - aldrich ) 1 
 ng / ml diluted with artificial tear eye drops for group t 
 were administered 3 times daily each for 3 weeks . corneal haze grading : the 
 level of haze in the cornea was evaluated by slit lamp biomicroscopy ( sl - d7 ) at 7 , 14 , 21 
 and 28 days after the surgery using two kinds of methods : the previously reported clinical 
 grading system   and a quantitative method . with 
 the clinical grading , grade 0 was a completely clear cornea ; grade 0.5 had a trace amount of 
 haze observed with careful oblique illumination ; grade 1 was a mild obscuration of the iris 
 details ; grade 2 was a more prominent haze not interfering with the visibility of fine iris 
 details ; grade 3 was a moderate obscuration of the iris and lens ; and grade 4 was complete 
 opacification of the stroma in the area of the ablation . haze grading was performed in a 
 blinded manner by three independent veterinarians . for quantitative haze grading , slit images were taken under standardized conditions : a 1 mm 
 wide , 14 mm long slit beam and a 45 angle from the temporal aspect of the cornea without 
 background illumination . then , each photograph was converted into an 8 bit gray - scale image 
 using digital image analysis ( imagej ver . the selected 
 area of the corneal section ( 100  3 pixel ) was isolated , and an intensity of 0 to 255 was 
 determined by averaging the gray - scale ( intensity ) indices of the individual pixels within 
 the area . immunofluorescence analyses : the beagle eyes were enucleated with the 
 conventional trans - scleral method after euthanasia . and then , the samples were fixed in 10% buffered 
 formalin and embedded in paraffin . immunofluorescence staining for -smooth muscle actin 
 ( sma ) , a marker for myofibroblasts , was performed . tissue sections ( 4 m ) 
 were incubated at room temperature with the monoclonal antibody for -sma ( m085101 , dako , 
 carpinteria , ca , u.s.a . ) at a 1:200 dilution in 1 pbs for 90 min and with a secondary 
 antibody ( alexa fluor 488 goat anti - mouse igg ; molecular probes , eugene , or , u.s.a . ) at a 
 dilution of 1:500 for 1 hr . tissues were mounted with mounting medium and dapi ( slowfade 
 gold antifade reagent , molecular probes ) to visualize the nuclei in the tissue sections . sections were viewed and photographed with a fluorescence microscope ( bx51 , olympus , tokyo , 
 japan ) equipped with a digital camera ( dp71 , olympus ) . quantification of -sma - positive cells : the -sma positive cells in six 
 randomly selected , non - overlapping , full - thickness central corneal columns , extending from 
 the anterior stromal surface to the posterior stromal surface were counted following a 
 method previously reported . statistical analysis : statistical analysis was performed with spss v20 for 
 windows ( spss inc . , data were expressed as the mean  standard 
 deviation ( sd ) , and the level of significance was p<0.05 . one way 
 analysis of variance ( anova ) with bonferroni s post - hoc assessment was used to test for the 
 significance of the objective haze grading and the total green color intensity between the 
 groups . in addition , in one - way repeated measures anova following pairwise comparison , 
 bonferroni s adjustment was performed to evaluate the objective haze grades against time in 
 the same group . for the clinical corneal haze grading , the values between groups were 
 compared using the kruskal - wallis analysis or friedman test with the wilcoxon signed rank 
 test . cell viability was over 95% at the concentration of 0 , 0.01 , 0.1 , 1 and 10 
 l / ml onion extract in vitro evaluation 
 ( data not shown ) . the 1% onion extract ointment showed no adverse effects and allergic 
 reaction , like blepharospasm , conjunctival hyperemia , corneal epithelial disorders and other 
 ocular abnormalities , when applied every 12 hr to the normal beagle cornea for 2 weeks . corneal haze developed after the air assisted lamellar keratectomy depending on each 
 treatment group ( fig . 2fig . 2.evaluation of corneal haze with a slit - lamp biomicroscopy . ( a ) pre - operative 
 evaluation in control group ( group c ) , ( b ) 7 days after surgery in the group c , ( c ) 14 
 days after surgery in the group c , ( d ) 21 days after surgery in the group c , ( e ) 28 
 days after surgery in the group c , ( f ) pre - operation in 1% prednisolone acetate 
 treatment group ( group p ) , ( g ) 7 days after surgery in the group p , ( h ) 14 days after 
 surgery in the group p , ( i ) 21 days after surgery in the group p , ( j ) 28 days after 
 surgery in the group p , ( k ) pre - operation in 1% onion extract ointment treatment group 
 ( group o ) , ( l ) 7 days after surgery in the group o , ( m ) 14 days after surgery in the 
 group o , ( n ) 21 days after surgery in the group o , ( o ) 28 ays after surgery in the 
 group o , ( p ) pre - operation tgf-1 1 ng/l treatment 
 group ( group t ) , ( q ) 7 days after surgery in the group t , ( r ) 14 days after surgery in 
 the group y , ( s ) 21 days after surgery in the group t , ( t ) 28 days after surgery in 
 the group o. ) . control corneas treated with the artificial tear eye drops ( group c ) had 
 significant developed corneal haze in clinical grading until 21 days after surgery ( day 14 ; 
 p=0.032 , day 21 ; p=0.041 and day 28 ; 
 p=0.210 ) compared with day 7 ( fig . mean grades for the clinical evaluation of corneal 
 haze at days 7 , 14 , 21 and 28 after surgery for each group . values 
 with a different superscript were significantly different ( p<0.05 ) 
 between groups in the same evaluation day . ) . topical application of 1% prednisolone acetate ( group p ) and 1% onion extract 
 ointment ( group o ) caused a statistically significant decrease in corneal haze in group p 
 ( day 14 ; p=0.021 , day 21 ; p=0.012 and day 28 ; 
 p=0.001 ) and in group o ( day 14 ; p=0.037 , day 21 ; 
 p=0.008 and day 28 ; p=0.003 ) compared with the same 
 groups for haze grading at day 7 . additionally , corneal haze was significantly increased in 
 the tgf-1 treated group ( group t ) ( day 14 ; p=0.002 , day 21 ; 
 p<0.001 and day 28 ; p<0.001 compared with the haze 
 grading at day 7 ) . for the degree of clinical corneal haze in each group , it decreased in 
 groups p and o from day 14 ( day 14 ; p=0.016 and p=0.007 , 
 day 21 ; p<0.001 and p=0.026 and day 28 ; 
 p=0.001 and p=0.011 , respectively ) compared with group 
 c. in addition , corneal haze significantly increased in group t at days 21 
 ( p=0.022 ) and 28 ( p=0.001 ) compared with group c. evaluation of corneal haze with a slit - lamp biomicroscopy . ( a ) pre - operative 
 evaluation in control group ( group c ) , ( b ) 7 days after surgery in the group c , ( c ) 14 
 days after surgery in the group c , ( d ) 21 days after surgery in the group c , ( e ) 28 
 days after surgery in the group c , ( f ) pre - operation in 1% prednisolone acetate 
 treatment group ( group p ) , ( g ) 7 days after surgery in the group p , ( h ) 14 days after 
 surgery in the group p , ( i ) 21 days after surgery in the group p , ( j ) 28 days after 
 surgery in the group p , ( k ) pre - operation in 1% onion extract ointment treatment group 
 ( group o ) , ( l ) 7 days after surgery in the group o , ( m ) 14 days after surgery in the 
 group o , ( n ) 21 days after surgery in the group o , ( o ) 28 ays after surgery in the 
 group o , ( p ) pre - operation tgf-1 1 ng/l treatment 
 group ( group t ) , ( q ) 7 days after surgery in the group t , ( r ) 14 days after surgery in 
 the group y , ( s ) 21 days after surgery in the group t , ( t ) 28 days after surgery in 
 the group o. clinical corneal haze grading . mean grades for the clinical evaluation of corneal 
 haze at days 7 , 14 , 21 and 28 after surgery for each group . values 
 with a different superscript were significantly different ( p<0.05 ) 
 between groups in the same evaluation day . corneal haze was observed beginning 7 days after surgery in all groups and appeared to peak 
 about 21 days after surgery in the control group with an objective evaluation method . the 
 total intensity of the grayscale units for the hazed cornea was significantly increased at 
 days 21 ( p<0.001 ) and 28 ( p<0.001 ) compared with day 
 7 in group c ( fig . . total intensity ( grayscale unites ) levels within the 
 corneal section at days 7 , 14 , 21 and 28 after surgery for all groups . a , b , 
 cvalues with a different superscript were significantly different 
 ( p<0.05 ) between groups in the same evaluation day . ) . the total intensity in groups p ( day 14 ; p=0.021 , day 21 ; 
 p<0.001 and day 28 ; p<0.001 ) and o ( day 14 ; 
 p=0.039 , day 21 ; p<0.001 and day 28 ; 
 p<0.001 ) was significantly decreased compared with that at day 7 . the 
 total intensity of the grayscale units in group t was significantly increased at days 14 
 ( p<0.001 ) , 21 ( p<0.001 ) and 28 
 ( p<0.001 ) compared with that at day 7 . total intensity ( grayscale unites ) levels within the 
 corneal section at days 7 , 14 , 21 and 28 after surgery for all groups . a , b , 
 cvalues with a different superscript were significantly different 
 ( p<0.05 ) between groups in the same evaluation day . the corneal haze was significantly decreased in groups 
 p ( p<0.001 ) and o ( p<0.001 ) at day 21 , 
 and in groups p ( p<0.001 ) and o ( p=0.002 ) at day 28 
 compared with group c. furthermore , the corneal haze was significantly increased in group t 
 at days 14 ( p<0.001 ) , 21 ( p<0.001 ) and 28 
 ( p=0.003 ) compared with group c. the results of immunohistochemical staining for -sma are shown in fig . 5fig . 5.immunohistochemistry for -smooth muscle actin ( sma ) ( 400 magnification , scale 
 bar=50 m ) . ( a ) stained nucleus with dapi in control group ( group c ) , 
 ( b ) -sma - positive cells ( green color ) in the group c , ( c ) merge image a and b , ( d ) 
 stained nucleus with dapi in prednisolone acetate treatment group ( group p ) , ( e ) 
 -sma - positive cells ( green color ) in the group p , ( f ) merge image d and e , ( g ) 
 stained nucleus with dapi in onion extract treatment group ( group o ) , ( h ) 
 -sma - positive cells ( green color ) in the group o , ( i ) merge image g and h , ( j ) 
 stained nucleus with dapi in tgf-1 treated group group ( group t ) , ( k ) -sma - positive 
 cells ( green color ) in the group t , ( l ) merge image j and k .. in group c , the corneas exhibited high numbers of -sma - positive myofibroblast 
 cells , mostly in the anterior stroma below the epithelium . topical application of 
 prednisolone acetate ( group p ) and onion extract ( group 
 o ) significantly reduced the numbers of -sma - positive cells in the stroma . in 
 contrast , tgf-1 application ( group t ) significantly increased the numbers of -sma - positive 
 cells compared with that in group c. immunohistochemistry for -smooth muscle actin ( sma ) ( 400 magnification , scale 
 bar=50 m ) . ( a ) stained nucleus with dapi in control group ( group c ) , 
 ( b ) -sma - positive cells ( green color ) in the group c , ( c ) merge image a and b , ( d ) 
 stained nucleus with dapi in prednisolone acetate treatment group ( group p ) , ( e ) 
 -sma - positive cells ( green color ) in the group p , ( f ) merge image d and e , ( g ) 
 stained nucleus with dapi in onion extract treatment group ( group o ) , ( h ) 
 -sma - positive cells ( green color ) in the group o , ( i ) merge image g and h , ( j ) 
 stained nucleus with dapi in tgf-1 treated group group ( group t ) , ( k ) -sma - positive 
 cells ( green color ) in the group t , ( l ) merge image j and k. the total green intensity of the entire stroma was significantly enhanced in group t 
 ( p<0.001 ) compared with that in group c ( fig . 6.the total intensity of green color was significantly lower in the prednisolone 
 acetate treatment ( group p ) and the onion extract treatment ( group o ) than control 
 ( group c ) . and , the total intensity of green color was significantly higher in the 
 tgf-1 treatment ( group t ) than the group c. values with a different 
 superscript were significantly different ( p<0.05 ) . ) . the total green intensity in groups p ( p<0.001 ) and o 
 ( p<0.001 ) was significantly lower than that in group c. the total intensity of green color was significantly lower in the prednisolone 
 acetate treatment ( group p ) and the onion extract treatment ( group o ) than control 
 ( group c ) . and , the total intensity of green color was significantly higher in the 
 tgf-1 treatment ( group t ) than the group c. values with a different 
 superscript were significantly different ( p<0.05 ) . formation of corneal haze involves the apoptosis of keratocytes   and transdifferentiation of keratocytes into myofibroblasts in 
 response to endogenous epithelial derived cytokines . tgf-1 directly activates keratocytes and leads to the formation of 
 myofibroblasts as well as the subsequent reformation of subepithelial stromal tissue . myofibroblasts scatter more light than that of 
 undifferentiated fibroblasts or keratocytes , not only from their nuclei , but also from their 
 cell bodies and dendritic processes . in 
 addition , this population of cells participates in extracellular matrix remodeling , 
 resulting in a denser and more disorganized extracellular matrix . intracellular microfilament fibers , such as f - actin and -smooth 
 muscle actin ( sma ) , were expressed much higher in myofibroblasts than in keratocytes . these 
 cellular components were enabled myofibroblasts to contract and close wounds , but also 
 rendered the cornea less translucent . collectively , these changes lead to a loss of corneal transparency . for a clear cornea , mitomycin c ( mmc ) is widely used intraoperatively by clinicians to 
 prevent prk - induced corneal haze , although there are several complications reported with its 
 topical use . there are no effective medicines to 
 control corneal haze , except for mmc treatments . because the application of steroid eye drop 
 occasionally results in rapid corneal stromal melting , use of these drugs for achieving 
 better corneal transparency is restricted . thus , we have shown the effects of onion extract 
 ointment in corneal haze prevention and suppression of myofibroblasts from stromal ablation 
 using the air assisted lamellar keratectomy for the development of new treatment and 
 prevention strategies . corneal fibroblasts were viable in the 10 
 l / ml concentration of the onion extract . there were no 
 adverse effects or allergic reactions for the 1% onion extract ointments . therefore , we used 
 this concentration of onion extract ointments in this study to evaluate efficacy of onion 
 extract . according to our results , corneal haze grading and expression of -sma - positive 
 cells were significantly decreased in the onion extract treated group compared with the 
 control group . because -sma is a specific marker for myofibroblasts , these results suggest 
 that onion extract ointment has suppressive effects on corneal haze . treatment with prednisolone acetate showed significant suppression of corneal haze compared 
 with the artificial tear treatment in this paper . topically applied steroids , acting as an 
 anti - inflammatory agent , have effectively suppressed corneal haze formation after excimer 
 laser keratectomy in experimental studies [ 17 , 24 ] . but , this reduction in haze appears to be due in 
 part to a delay in the wound - healing response . also , glucocorticoids increase the lytic action of corneal collagenase , suggesting that this 
 effect might be responsible for the corneal destruction in clinical conditions . accordingly , the onion extract ointment could be used 
 more safely than steroid eye drops , which would be induced corneal melting . onion ( allium cepae ) extract contains a great amount of antioxidant 
 phytochemicals , sulfur and other numerous phenolic compounds . these compounds have been reported to be effective in cardiovascular diseases 
 because of their hypolipidemic , anti - hypertensive , anti - diabetic and antithrombotic effects , 
 and to possess many other biological activities including antimicrobial , antioxidant , 
 anticarcinogenic , antimutagenic , antiasthmatic , immunomodulatory and probiotic activities 
 . especially , onion extract was shown to have 
 fibroblast - inhibiting properties , to reduce proliferative activity , and to produce 
 substances in the extracellular matrix . recently , commercial products composed of onion extract have been used to reduce scar 
 formation on the skin . according to the results 
 of this paper , onion extract suppressed the differentiation of myofibroblasts , and as a 
 result , corneal haze developed significantly less than that of the control . onion extract 
 would be a good therapeutic candidate as a new medicine for corneal haze suppression . tgf-1 , a potent profibrotic cytokine , is a key 
 regulator for the differentiation of myofibroblasts during corneal wound healing . it 
 directly activates keratocytes and leads to the formation of myofibroblasts as well as the 
 subsequent reformation of the subepithelial stroma . consequently , these mechanisms could promote the clinical expression of 
 corneal haze after corneal surgery . in our results , corneal haze furthermore , one experiment 
 showed the prevention of prk - induced haze through the use of anti - tgf-1 antibodies . thus , the suppression of tgf-1 expression is 
 critical in the prevention of corneal haze . fibroblasts differentiate into myofibroblasts through a smad 2/3 signaling pathway and 
 enhance nadph oxidases ( nox ) 4-derived reactive oxygen species ( ros ) signaling cascades 
 . depletion of nox4 , an essential mediator of 
 smad2/3 transcription factor activation in response to tgf- 1 , down - regulates -sma mrna , 
 and overexpression of nox4 induces -sma expression . the corneal haze grade was significantly lower in the onion extract treated group than in 
 the control group , and the expression of -sma was also down - regulated by the onion extract 
 treatments shown in the results of this study . among the many flavonoid compounds , quercetin 
 is a major component of onion extract , and it 
 has been shown to have powerful antioxidative activity with metal ion binding properties and 
 radical scavenging abilities . in addition , 
 quercetin has a scavenging effect on superoxide anions and hydroxyl radicals , and it 
 prevents lipid peroxidation by blocking the action of xanthine oxidase and chelating iron 
 . these effects could have important roles in 
 the suppressive effect of onion extract against corneal haze formation . these results 
 suggest that onion extract could block tgf-1 signaling cascades by scavenging ros to reduce 
 -sma expression and subsequently corneal haze development . the limitation of this study is that the evaluation time was short and there was not enough 
 to prove exact mechanism of onion extract ointment against corneal haze formation . , onion extract ointment could be useful as the therapeutic in the suppression of 
 corneal haze development after applying the air assisted lamellar keratectomy through the 
 down - regulation of fibroblast transdifferentiation into myofibroblasts .
this study evaluated the effect of onion extract on corneal haze suppression 
 after applying the air assisted lamellar keratectomy . 
 the air assisted lamellar 
 keratectomy was performed on 24 canine eyes . 
 they were treated with an artificial tear 
 ( group c ) , prednisolone acetate ( group p ) , onion extract ( group o ) and tgf-1 ( group t ) 
 three times per day from 7 to 28 days after the surgery . 
 corneal haze occurred on the all 
 eyes and was observed beginning 7 days after the surgery . 
 the haze was significantly 
 decreased in groups p and o from day 14 compared with the group c using the clinical 
 ( group p ; p=0.021 , group o ; p=0.037 ) and objective 
 evaluation method ( group p ; p=0.021 , group o ; p=0.039 ) . 
 in contrast , it was significantly increased in group t from day 14 compared with group c 
 based on the clinical ( p=0.002 ) and objective evaluation method 
 ( p<0.001 ) . 
 subsequently , these eyes were enucleated after 
 euthanasia , and immunohistochemistry with -sma antibodies was done . 
 the total green 
 intensity for -sma was significantly more expressed in group t and significantly less 
 expressed in groups p and o than in group c. onion extract could have potential as a 
 therapeutic in preventing corneal haze development by suppressing the differentiation of 
 fibroblasts into myofibroblasts .