this prospective , comparative , nonrandomized study included a total of 16 eyes from 16 patients with corneal edema resulting either from pseudophakic bullous keratopathy or fuchs ' endothelial dystrophy . all subjects underwent either dlek or dsek at the samsung medical center between june 2005 and september 2007 . individuals with significant ocular stromal scarring were excluded , while individuals with a history of well - controlled glaucoma , cataracts , and other comorbidities were allowed to participate . ours was a non - randomized study , wherein dlek cases were performed prior to dsek , as dsek was developed at a later timepoint . three subjects were excluded from the analysis due to primary graft failure : one individual in the dlek group and two from the dsek group . the remaining 13 patients were followed for at least one year , and all surgeries were performed by a single surgeon . snellen uncorrected visual acuity ( ucva ) , best corrected visual acuity ( bcva ) , refractive astigmatism , corneal topography ( orbscan ii , bausch & lomb , rochester , ny , usa ) , ultrasonic pachymetry ( ultrapach ; eye technology , st . paul , mn , usa ) , and endothelial cell count ( sp-8000 ; konan medical inc . , nishinomiya , japan ) were performed preoperatively and at postoperative months 1 , 3 , 6 , and 12 . the rotating scheimpflug camera ( pentacam ; oculus , wetzlar , germany ) was used to evaluate the corneal interface opacity at postoperative month 12 . , dayton , oh , usa ) was also performed 1 year after surgery . for each subject , this examiner extracted densitometry standard output values from the captured images in a blinded fashion . image degrees of 45 to 225 and 135 to 315 were used for the right eye , and 225 to 45 and 315 to 135 for the left eye . on each image , measurement points were manually located by cursor at the center of the cornea , and at points 1.5 mm and 3.0 mm left and right of center . chicago , il , usa ) . the mann - whitney u - test was used to compare clinical outcomes between dlek and dsek at different postoperative time points . p - values of < 0.05 were defined as statistically significant in all cases . following a 5.0 mm scleral incision in the recipient cornea , deep lamellar dissection was performed to approximately 80% of the corneal thickness using a dissecting spatula ( dorc international , zuidland , netherlands ) . the epithelial surface was marked using with methylene blue on a 8.0 mm template , and the posterior lamellar disc was excised from the cornea with curved plk scissors ( dorc international ) over 360 degrees . the donor cornea was mounted on an artificial anterior chamber ( bausch & lomb , st . louis , mo , usa ) , dissected in a similar way , and punched out with trephine so to match corneal size between recipient and donor . an 8.0 mm prepared donor posterior disc was folded endothelium to endothelium ( separated by viscoelastics [ hyaluronate sodium 10 mg/1 ml ; hyal-2000 , lg life sciences , daejeon , korea ] ) , and then inserted into the anterior chamber through the scleral incision . after unfolding , the donor disc was attached to the recipient stromal bed by injecting air underneath the graft . the scleral incision was then sutured with 10 - 0 nylon , and the previously injected air was replaced with balanced salt solution ( bss ; alcon laboratories , fort worth , tx , usa ) after 15 minutes in order to promote adherence between donor and recipient stromal surfaces . a 5-mm superior scleral tunnel incision was made in the recipient cornea , and the epithelial surface marked with a 8.0 mm template for descemet membrane stripping . the descemet membrane was scored and stripped using a reverse - sinskey hook within the epithelial marking . the donor disc was then folded with forceps , inserted into the anterior chamber , and unfolded . finally , an air bubble was injected to attach the donor disc to the recipient stromal bed . the scleral wound was closed with 10 - 0 nylon sutures , and the previously injected air was replaced with bss after 15 minutes . following a 5.0 mm scleral incision in the recipient cornea , deep lamellar dissection was performed to approximately 80% of the corneal thickness using a dissecting spatula ( dorc international , zuidland , netherlands ) . the epithelial surface was marked using with methylene blue on a 8.0 mm template , and the posterior lamellar disc was excised from the cornea with curved plk scissors ( dorc international ) over 360 degrees . the donor cornea was mounted on an artificial anterior chamber ( bausch & lomb , st . louis , mo , usa ) , dissected in a similar way , and punched out with trephine so to match corneal size between recipient and donor . an 8.0 mm prepared donor posterior disc was folded endothelium to endothelium ( separated by viscoelastics [ hyaluronate sodium 10 mg/1 ml ; hyal-2000 , lg life sciences , daejeon , korea ] ) , and then inserted into the anterior chamber through the scleral incision . after unfolding , the donor disc was attached to the recipient stromal bed by injecting air underneath the graft . the scleral incision was then sutured with 10 - 0 nylon , and the previously injected air was replaced with balanced salt solution ( bss ; alcon laboratories , fort worth , tx , usa ) after 15 minutes in order to promote adherence between donor and recipient stromal surfaces . a 5-mm superior scleral tunnel incision was made in the recipient cornea , and the epithelial surface marked with a 8.0 mm template for descemet membrane stripping . the descemet membrane was scored and stripped using a reverse - sinskey hook within the epithelial marking . the donor disc was then folded with forceps , inserted into the anterior chamber , and unfolded . finally , an air bubble was injected to attach the donor disc to the recipient stromal bed . the scleral wound was closed with 10 - 0 nylon sutures , and the previously injected air was replaced with bss after 15 minutes . following a 5.0 mm scleral incision in the recipient cornea , deep lamellar dissection was performed to approximately 80% of the corneal thickness using a dissecting spatula ( dorc international , zuidland , netherlands ) . the epithelial surface was marked using with methylene blue on a 8.0 mm template , and the posterior lamellar disc was excised from the cornea with curved plk scissors ( dorc international ) over 360 degrees . the donor cornea was mounted on an artificial anterior chamber ( bausch & lomb , st . louis , mo , usa ) , dissected in a similar way , and punched out with trephine so to match corneal size between recipient and donor . an 8.0 mm prepared donor posterior disc was folded endothelium to endothelium ( separated by viscoelastics [ hyaluronate sodium 10 mg/1 ml ; hyal-2000 , lg life sciences , daejeon , korea ] ) , and then inserted into the anterior chamber through the scleral incision . after unfolding , the donor disc was attached to the recipient stromal bed by injecting air underneath the graft . the scleral incision was then sutured with 10 - 0 nylon , and the previously injected air was replaced with balanced salt solution ( bss ; alcon laboratories , fort worth , tx , usa ) after 15 minutes in order to promote adherence between donor and recipient stromal surfaces . donor discs were prepared as described above ( size 8.0 mm ) . a 5-mm superior scleral tunnel incision was made in the recipient cornea , and the epithelial surface marked with a 8.0 mm template for descemet membrane stripping . the descemet membrane was scored and stripped using a reverse - sinskey hook within the epithelial marking . the donor disc was then folded with forceps , inserted into the anterior chamber , and unfolded . finally , an air bubble was injected to attach the donor disc to the recipient stromal bed . the scleral wound was closed with 10 - 0 nylon sutures , and the previously injected air was replaced with bss after 15 minutes . this study included a total of 16 eyes from 16 patients aged 53 to 78 years . the mean follow - up was 45.56.89 months ( with a range of 32 to 52 months ) for the dlek group and 13.62.7 months ( with a range of 11 to 17 months ) for the dsek group . table 1 summarizes the patients ' preoperative characteristics and operative data . because of the significant difference in follow up period between groups , only data from the first post operative year were analyzed in regards to visual outcome , endothelial cell count , donor - recipient interface opacity , contrast sensitivity testing and complication rates . the mean preoperative bcva was 20/1000 ( logarithm of the minimum angle of resolution [ logmar ] , 1.720.27 ) for the dsek group and 20/1000 ( logmar , 1.700.30 ) for the dlek group , with no statistically significant difference occurring ( p>0.05 ) . although statistically insignificant , the postoperative ucva and bcva for individuals in the dsek group were observed to be better during the entire follow up period ( fig . the bcva was 20/70 ( logmar , 0.550.28 ; range , 20/500 to 20/30 ) for the dlek group and 20/50 ( logmar , 0.400.35 ; range , 20/200 to 20/25 ) for the dsek group , with no statistically significant difference occurring ( p=0.642 ) ( table 2 ) . table 2 shows the mean spherical equivalents and refractive astigmatisms between the two groups at postoperative month 12 . the mean spherical equivalents between the 2 groups did not vary significantly ( p=0.641 ) , although the dsek group was found to be slightly more hyperopic . corneal endothelial cell counts were evaluated at postoperative month 12 : the donor endothelial cell count was 2507416 cells / mm for the dlek group and 2415275 cells / mm for the dsek groups , with no statistically significant difference between groups . at postoperative month 12 , the corresponding endothelial densities were 1849494 and 1643417 cells / mm , representing cell losses of 26.2% and 31.9% for the dlek and dsek groups , respectively . no significant differences in endothelial cell counts or endothelial cell losses were identified between groups 12 months after surgery ( p=0.620 , p=0.470 ) ( table 2 ; fig . preoperative corneal thickness also did not significantly differ between groups ( p=0.590 ) , with thicknesses assessed at 707169 for the dlek group and 774130 m for the dsek group . however , a statistically significant difference in mean corneal thickness was observed at postoperative month 12 . at this time , the mean corneal thickness was 553139 m among individuals in the dlek group and 67769 m among individuals in the dsek groups ( p=0.042 ) ( table 2 ) . the donor - recipient interface opacity was assessed by averaging data from 10 different pentacam - measured points . at postoperative month 12 , the dsek group exhibited slightly less interface opacity than the dlek group , although these results were not significant ( p=0.576 ) ( table 2 ) and may have occurred from stripping technique performed in the dsek group . at all spatial frequencies , no significant differences in postoperative contrast sensitivity testing were identified ( p>0.05 ) , with fig . table 3 summarizes the data regarding incidence of intra- and postoperative complications occurring after dlek and dsek surgeries . disc dislocation occurred in two individuals ( 28.5% ) who underwent dlek and one individual who underwent dsek , all of which were rescued with air injection . due to primary donor failure , one subject ( 12.5% ) in the dlek group and two subjects ( 25.0% ) in the dsek group required secondary penetrating keratoplasty due to primary donor failure . recently , a number of comparative studies have compared dlek and dsek [ 6 - 8 ] . a lamellar corneal transplantation that specifically replaces the diseased endothelium may be performed using either method . interestingly , the cause of endothelial dysfunction appears to differ between asians and caucasians , with pseudophakic bullous keratopathy occurring more commonly in asians and fuchs ' endothelial dystrophy in caucasians . as most previously published studies have primarily only enrolled caucasian subjects , the present study is especially significant , as it was performed in ethnic koreans and is , to the best of our knowledge , the first comparative study of dlek and dsek in asians . in this cohort , the average bcva value at postoperative month 12 was 20/70 for dlek and 20/50 for dsek , which are not as good as previously reported values [ 2,9 - 13 ] . however , given the relatively high prevalence of vision - limiting diseases in the enrolled subjects ( such as glaucoma ) and the relatively low preoperative potential acuity meter values ( 20/60 ) , we contend that the visual outcomes achieved here were more than satisfactory . moreover , when we compared the visual outcomes between groups , no significant differences in bcva were identified at postoperative months 3 , 6 , or 12 , with these results mirroring those of previously published reports . furthermore , the visual outcomes achieved here were better than those previously reported for pkp , suggesting that plk may be a better treatment option for patients with endothelial dysfunction . in terms of refraction , the dsek group showed a tendency toward hyperopia ( p=0.641 ) . it was recently reported that thickness changes in donor grafts might induce a hyperopic shift , and that this hyperopia decreases with changes in posterior corneal curvature . data from another study also indicate that donor lenticules with thicker peripheries and thinner centers may act as minus lenses , thus producing a hyperopic shift . such an effect may have been minimized in the dlek group in our study , as the donor lenticules were similar in shape to the recipient stromal beds , thereby reducing differences in the thickness between the central and peripheral cornea and ultimately ensuring a good fit . moreover , the mean refractive astigmatism did not significantly differ between groups , which is consistent with previous reports . the differences in endothelial cell loss between the dlek and dsek groups were not observed to be statistically significant . at 12 months after surgery , the average percentage of endothelium loss was 26.2% in the dlek group and 31.9% in the dsek groups . terry and ousley   reported an average cell loss of 29% at 12 months after small - incision surgery and 28% after large - incision dlek surgery . reported a losses of 26% after large - incision posterior lamellar keratoplasty , while data from gorovoy   showed losses of 40% after small - incision dsek surgery . overall , our findings concur with these results , although the subjects in our study experienced minimal progressive cell losses between postoperative months 6 and 12 , which is different from previous reports . terry et al .   demonstrated that endothelial cell loss after plk may occur as late as one to two years postoperatively , with donor cell loss substantially accelerating with time . consequently , long - term data is needed to adequately categorize postoperative cell loss rates . in the present study , we assessed donor - recipient interface opacity and contrast sensitivity , neither of which has been well characterized to date . interface opacity may induce higher - order aberrations , contrast sensitivity losses , and visual impairment . accordingly , we measured interface opacity ( using pentacam ) and contrast sensitivity , and analyzed the resulting data for any differences between groups . although the dlek group exhibited slightly more interface opacity , the difference between the two groups was not statistically significant . in terms of contrast sensitivity since dlek requires additional recipient stromal dissection , we expected that the dsek group would experience less interface opacity and have better contrast sensitivity . in a previous study , the mean contrast sensitivity was found to be similar between candidates undergoing penetrating keratoplasty and deep anterior lamellar keratoplasty . due to the dearth of other studies directly comparing the postoperative interface opacity and contrast sensitivity after dlek and dsek , donor disc dislocation occurred in one subject ( 16.6% ) in the dsek group and in two subjects ( 28.5% ) in the dlek group . in all cases , donor - lenticule separation was treated by graft repositioning via air or gas bubble tamponade . the donor dislocation rate that occurred here is greater than in the study from terry and ousley ( who reported a donor dislocation rate of 4% after dlek ) , suggesting that the difference may result from surgeon experience . nevertheless , the rate observed in the present study is consistent with the reported dislocation incidences in other studies ( range , 14% to 25% ) . moreover , the dislocation rates observed here were not significantly different between the dlek and dsek groups , which supports the findings of bahar et al . however , other studies have concluded that the incidence of dislocation is greater in dsek than dlek , as dsek has only one manually dissected surface and consequently a smoother donor - recipient interface . in summary , our study directly compares the clinical outcomes of dlek and dsek , when performed as initial cases by a single surgeon . despite the small case number , we believe that our results reflect an accurate comparison , as we attempted to eliminate the bias resulting from sufficient learning experience of dlek . our data indicate that both dlek and dsek produce favorable clinical outcomes at 12 months postoperatively , and that the two techniques did not significantly differ in subject visual acuity , refraction , endothelial cell loss , and complication rates . interestingly , no significant differences were identified in interface opacity and contrast sensitivity between the two techniques . further studies with larger study populations and longer follow - up periods are required to verify our findings .
purposeto compare clinical outcomes after deep lamellar endothelial keratoplasty ( dlek ) with descemet stripping endothelial keratoplasty ( dsek ) performed as initial cases by a single surgeon.methodssixteen patients with corneal endothelial were enrolled . 
 eight patients ( 8 eyes ) underwent dlek and 8 patients ( 8 eyes ) dsek . 
 we measured uncorrected visual acuity , best corrected visual acuity ( bcva ) , manifest refraction , corneal endothelial count , interface opacity via schiempflug imaging , and contrast sensitivity , as well as tracked postoperative complications over the first postoperative year.resultsprimary graft failure occurred in two dlek cases and one dsek case , all of which were excluded for further analysis . 
 the average 12-month postoperative bcva was 20/70 in the dlek group and 20/50 in the dsek group , with the difference not statistically significant . 
 no significant differences were identified between the 2 groups in terms of mean spherical equivalent and refractive astigmatism , although individuals in the dsek group tended toward hyperopia . 
 the average endothelial cell count at postoperative month 12 was 1849494 in the dlek group and 1643417 cells / mm2 in the dsek group , representing cell losses of 26.2% and 31.9% , respectively . 
 no significant differences in endothelial cell count or endothelial cell loss were observed between groups . 
 early postoperative donor disc dislocation occurred in two eyes after dlek and one eye after dsek . 
 interface opacities and contrast sensitivities were similarly not significantly different between groups.conclusionsno significant differences in any assessed clinical outcome were observed between individuals undergoing dlek and dsek , when performed as initial cases by a single surgeon .