it demonstrates an elastotic degeneration of the collagen as a result of excessive ultraviolet exposure .
majority of pterygium occurs in the nasal side , but it is not uncommon to encounter double - head pterygium in the  pterygium belt
pterygium can affect vision by causing tear film instability , inducing corneal astigmatism or blocking the visual axis .
simple excision of pterygium leaving behind an area of bare sclera has a high recurrence rate ranging from 24 to 89%
. therefore , there are many adopted methods to augment the long - term success of pterygium surgery .
commonly used adjuvants in the literature include conjunctival autograft ( cau ) , limbal - conjunctival autograft ( lcau ) , mitomycin c ( mmc ) , and amniotic membrane transplantation ( amt ) .
lcau was showed to be superior to mmc in pterygium surgery in a 10-year follow - up study of a randomized controlled trial published recently in the literature [ 8 , 9 ] .
comparison between cau and lcau reported similar success between the two methods in primary pterygium and a superior effectiveness of lcau in recurrent cases .
the present study is a 12-year follow - up study comparing the long - term outcomes and complications of double - head pterygium surgery with cau to one  head  and mmc application to the opposite  head  of the same eye .
this is a follow - up study of a comparative interventional trial , which was approved by the research ethics committees of the chinese university of hong kong and adhered to the tenets of the declaration of helsinki . in the original study ,
39 eyes of 36 patients with double - head pterygium were randomized to receive cau to one  head  of the pterygium and mmc application by being defaulted to the opposite  head .
 randomization was done by choosing between two sealed envelopes , labeled  nasal pterygium with ca  in one and  nasal pterygium with mmc  in another .
the same surgeon ( ey ) performed all surgeries at hong kong eye hospital during the period of may 2000 to june 2001 . in this follow - up study , patients in this cohort were invited back to the hospital for clinical examination in september to december 2013 to document the long - term outcomes and complications of the two adjuvants in pterygium surgery .
clinical examination of the anterior segment and optic disc , intraocular pressure measurement and slit - lamp photography were performed .
this follow - up study was approved by the institutional review board of the hospital authority . in the original study , pterygium size and morphology
size of pterygium was measured from limbus to the head of pterygium and the longest diameter was taken .
pterygium was graded into atrophic , intermediate , and fleshy according to the visualization of episcleral vessels underneath the pterygium body with clearly distinguished vessels seen in atrophic type and totally obscured view in fleshy type .
intraoperative mmc ( 0.02% ) was applied directly to the bare sclera using moist vitreous sponges for 5 minutes .
the site of mmc application was irrigated thoroughly with at least 50  ml of balanced salt solution .
the conjunctiva peripheral to the excised pterygium was then sutured to the episclera . on the pterygium head receiving cau ,
a free conjunctival graft was harvested from the superior region of the same eye with dimensions 1  mm larger than the recipient bed .
the free graft was then secured to the recipient bed respecting its polarity with interrupted 8.0 polyglactin .
postoperative treatment included a topical steroid ( dexamethasone ) and antibiotic ( chloramphenicol ) four times daily for 4 weeks .
the first - year result of the original study was presented in a local scientific conference in hong kong without publication in the literature . in the current follow - up study ,
grade a represents the appearance of the operated site is not different from the normal appearance ; grade b represents some fine episcleral vessels in the excised area extend up to but not beyond the limbus and without fibrous tissue ; grade c represents additional fibrous tissue is in the excised area but does not invade the cornea ; grade d represents fibrovascular tissue invades the cornea and was defined as recurrence in this follow - up study . two independent assessors ( rw and el ) , who were blinded to treatment each pterygium received , determined disease recurrence and conjunctival bed grading .
a lesion was considered as  recurrence  if one assessor agreed on a disease relapse . as for the conjunctival bed status ,
the higher grading would be chosen if there was a discrepancy between grading scored by the two assessors .
long - term complications related to cau or mmc involving the cornea and scleral bed are the secondary outcome measures of the study .
information regarding recurrence and complications by the first postoperative year was traced from the medical records and record of the original study .
statistical analysis was performed using pasw software version 18.0 ( spss / ibm , inc . ,
chi - square and mann - whitney u test were used to compare qualitative and quantitative variables , respectively , between groups .
there were 39 eyes ( 78 pterygia ) of 36 patients recruited in the original study .
the mean follow - up period was 155  4 months ( 12.9 years ) .
the response rate was 82.1% with 32 eyes ( 64 pterygia ) completing this follow - up study .
six patients ( 6 eyes ) passed away before this follow - up study ; one patient ( 1 eye ) was lost to contact .
twenty - seven eyes of 25 patients were assessed in the clinic , while disease recurrence was determined from telephone interview in 4 patients ( 5 eyes ) who were unable to attend the clinic .
supplementary photographs were obtained from those 4 patients for determination of recurrence , but conjunctival bed grading was not performed in them .
demographic and clinical data of patients who completed and defaulted the follow - up study was summarized in table 1 .
there was no significant difference in pterygium size ( p = 0.412 ) , morphology ( p = 0.251 ) , and type ( p = 0.792 ) between the completed and defaulted patients apart from age , which was significantly older in the defaulted patients ( p = 0.016 ) .
preoperative characteristics of the pterygium between the treatment groups in the current follow - up study were summarized in table 2 .
there was no significant difference in size ( p = 0.403 ) , morphology ( p = 0.749 ) , and type ( p = 0.740 ) of the pterygium between the cau and mmc groups .
thirteen nasal pterygia were treated with cau after excision , and 19 nasal pterygia were treated with mmc .
moreover , there was no significant difference in size ( p = 0.512 ) , morphology ( p = 0.414 ) , and type ( p = 0.740 ) between nasal and temporal pterygium .
the cohen 's kappa coefficient , which is a statistical measure of interassessors agreement , was 0.81 signifying almost perfect agreement between the two assessors in the current study .
recurrence of pterygium was noted in 1 case in the cau group ( 2.56% ) and 6 cases in the mmc group ( 15.4% ) one year after the operation .
the difference in recurrence rate was statistically significant between the two treatment groups ( p = 0.048 ) .
significant difference in recurrence rate was also noted between the two groups 12 years after the pterygium operation . there were 2 cases of recurrence in the cau group ( 6.25% ) , and 9 cases in the mmc group
five recurrent cases were nasal pterygium , and 6 recurrent cases were located on the temporal side ( p = 740 ) . among the cases with recurrence observed , all but one were primary pterygium before the operation performed in the study ( p = 0.434 ) .
it was excised and treated with mmc in the original study , but it recurred 3 months afterwards .
all the recurrent cases did not undergo further pterygium operations and were managed conservatively according to the patients ' preference .
grading of conjunctival bed was summarized in table 4 . among the eyes with no disease recurrence on either side ( 38 pterygia in 19 eyes ) ,
conjunctival beds previously treated with mmc were graded higher than the beds covered with cau in the same eye ( p = 0.024 ) .
eight eyes showed higher conjunctival bed grades after mmc treatment than that after cau treatment 12 years after the surgery .
difference in conjunctival bed grades was not significant between sites ( nasal or temporal ) of pterygium ( p = 0.333 ) .
diffuse punctate epithelial erosions were seen in 8 eyes ( 20.5% ) and all resolved with topical lubricants .
corneal dellen , conjunctival cyst , pyogenic granuloma , symblepharon , and subconjunctival fibrosis were not observed at sites previously covered with autograft and at the harvest site of cau . as for the mmc group ,
severe complications including scleral thinning and melting , corneal decompensation , and glaucoma were not detected in any patient attending the follow - up at 12 years after the double - head pterygium surgery .
there are various techniques developed to minimize disease recurrence with cau and mmc the two most commonly adopted adjuvants .
adjuvants including cau and mmc in pterygium surgery have been summarized in a recently published review article .
cau has been shown to be an effective procedure , with recurrence rates ranging from 2% to 39% after primary pterygium excision [ 11 , 1315 ] .
on the contrary , mmc is an alkylating agent that prevents cellular activity by inhibiting dna synthesis .
previous studies showed recurrence rates varying from 3% to 38% in primary pterygium when mmc was used intraoperatively [ 6 , 1618 ] .
however , the use of mmc may lead to severe ocular complications including scleral thinning and necrosis , corneal decompensation , and glaucoma [ 1922 ] .
the current study had a high response rate with more than 80% of patients participating in the follow - up study .
the double - head pterygium in each eye received cau on one side and mmc on the other as adjuncts , and the pairwise comparison of treatment effects in the same eye minimized interpersonal variability as a confounder . randomizing
the treatment arm to either nasal or temporal pterygium also reduced confounding effect arising from the lesion site .
although there was no difference in the preoperative characteristic of pterygium , such as the size , site , morphology , and type between the 2 study groups , the list of confounding variables is not exhaustive .
it is important to note that direct comparison among different studies is difficult because there are variations in surgical techniques including extent of excision and application of mmc , follow - up duration , and definition of recurrence . the recurrence rate of pterygium after cau was significantly lower than that of mmc in the current study .
several studies in the literature demonstrated a trend favoring cau over intraoperative mmc for prevention of pterygium recurrence [ 15 , 16 , 23 ] .
similar findings were observed in a recently published randomized controlled study with 10-year follow - up , which showed a recurrent rate of 6.9% after lcau and 25.5% after mmc . by including the limbal epithelium in the conjunctival graft
the 10-year recurrence rates after lcau and mmc reported by young et al . were similar to the 12-years recurrence rates after cau and mmc in our study .
reports have shown that both lcau and cau were effective in preventing recurrence after pterygium excision , though lcau showed slight advantage over cau in recurrence rate in recurrent pterygium [ 10 , 24 ] .
the current study demonstrated a comparable success with cau in terms of long - term pterygium recurrence rate and the lack of complications such as corneal dellen , conjunctival cyst , pyogenic granuloma , symblepharon , and subconjunctival fibrosis .
conjunctival bed grading was found to be significantly higher after mmc treatment when compared to that after cau .
this finding was consistent with a higher recurrence rate after mmc treatment as shown in current study .
although there was no long - term complication observed between the two adjuvants in this study , adjuvant mmc treatment after pterygium excision was shown to be inferior to cau in preventing recurrence .
it is interested to see that there was an ongoing recurrence in the mmc group ( 3 eyes ) after the first 1 year of pterygium excision , while all the recurrence took place within 1 year in the cau group . in a 10-year follow - up study by young et al .
, there was 1 recurrent case in the lcau group and 3 recurrent cases in the mmc group after the first postoperative year . on the contrary , koranyi et al
. did not observe any recurrence after the 12 months visit in a 4-year comparative study between cau and mmc in primary pterygium surgery .
survival curve analysis also showed that there was a 97% chance that there would be a recurrence within 1 year of pterygium removal .
the ongoing recurrence observed could be the result of persistent ocular inflammation or irritation in the site previously managed with intraoperative mmc while leaving the bare sclera behind .
, we were not able to identify the exact time of pterygium recurrence during the extended follow - up period because all the patients were discharged from the original study ( 1 year ) before they were invited back for the current follow - up study
. nevertheless , majority of the recurrence cases occurred within the first postoperative year ; this may signify the need to monitor patient who underwent pterygium excision for at least a year before discharge .
moreover , this study was also a noncomparative analysis of using cau and mmc in double - head pterygium surgery . in the current study ,
recurrence was found in 28% of our cases ( 9 of the 32 eyes ) .
two eyes had recurrence over both heads , and 7 eyes had recurrence over either head treated with mmc previously .
other options in double - head pterygium surgery included rotational cau , split - cau , sequential cau , mmc , and amt .
all of these treatments aimed at preventing recurrence despite the larger conjunctival defects remained after removal of the two heads . a previous interventional cohort in our hospital involved combining rotational cau and cau .
rotational cau was harvested from the larger pterygium and placed over the conjunctival defect of the smaller pterygium with 180-degree rotation .
the defect of the larger pterygium was then covered with cau harvested from the superior bulbar conjunctiva . another way to cover the bare sclera was using split - cau .
split - cau aimed at covering both conjunctival defects with a large cau divided from the superior bulbar conjunctiva .
no recurrence was found in a retrospective evaluation of 7 eyes over a mean follow - up period of 18 months .
however , adequate exposure may be difficult in small chinese eyes . by performing sequential cau to each head separately ,
a canadian group showed only 1 nasal recurrence ( 5.6% ) after 2 years in a retrospective study of 9 eyes .
this allowed cau to each head but avoiding extensive cau dissection . on the other hand ,
intraoperative mmc application was used solely after double - head pterygium excision in a case series of 13 eyes . in this case series , 1 eye ( 8.0% ) had recurrence in a follow - up period of 3 years .
similar recurrence rate ( 9.1% ) was shown with amt after extensive conjunctival excision of 11 eyes observed for 1 year .
although the results of our study appeared to be inferior to other studies in the literature , most studies were limited by the small sample size , short follow - up duration , and retrospective nature , making direct comparison difficult among them .
this is understandable as the reported incidence of double - head pterygium was less than 3% , making case recruitment difficult .
the current method we adopted for double - head pterygium surgery is combining cau with rotational cau or amt to cover the bare sclera . in conclusion , both cau and mmc were shown to be safe adjuvants in pterygium surgery .
cau appeared to be a better choice with lower recurrence rate and better conjunctival appearance when compared to mmc .
bare sclera pterygium excision in the presence of adjuvant mmc should not be performed given the significantly high rate of long - term recurrence .
 
 purpose . the study aims to compare the long - term outcome of conjunctival autograft ( cau ) and mitomycin c ( mmc ) in double - head pterygium surgery 
 . methods . 
 this is a follow - up study of a comparative interventional trial . 
 thirty - nine eyes of the 36 patients with double - head pterygium excision in the original study 12 years ago were recruited for clinical assessment . 
 seven out of the 36 patients were lost . in the original study , 
 each eye with double - head pterygium was randomized to have pterygium excision with cau on one  head  ( temporal or nasal ) and mmc on the other  head .  
 all patients were invited for clinical assessment for conjunctival bed status and the presence of pterygium recurrence in the current study . 
 results . 
 there was no significant difference between the size , morphology , and type of pterygium among the two treatment groups . 
 the recurrence rate of cau group and mmc group 12 years after excision was 6.3% and 28.1% , respectively ( p = 0.020 ) . among eyes without recurrence , 
 the conjunctival bed was graded higher in the mmc group than the cau group ( p = 0.024 ) . 
 conclusion . 
 the use of conjunctival autograft has a significantly lower long - term recurrence rate than mitomycin c in double - head pterygium surgery . 
1. Introduction
2. Methods
3. Results
4. Discussion