the descemet 's stripping automated endothelial keratoplasty ( dsaek ) procedure is primarily used to treat corneal endothelial dystrophies , and more recently to treat endothelial failure in previous penetrating keratoplasty .
descemet 's membrane and endothelium are removed through a small incision and replaced with donor tissue , which adheres to the recipient 's inner corneal stroma .
the advantages of the dsaek procedure when compared with the traditional penetrating keratoplasty ( pk ) technique have been previously described in the literature [ 1 , 38 ] .
the major postoperative complication of the dsaek procedure is dislocation of the donor tissue from the corneal transplant bed , which has been reported to happen in 427% of patients [ 1 , 5 , 7 , 9 , 10 ] .
donor detachments are most likely attributed to surgeon error or a lack of donor tissue viability . in ontario , procured donor tissue is sent to the eye bank of canada before being shipped to the transplanting surgeons for implantation .
a period of time , typically hours , passes between the death of the donor and enucleation of the eye , and between enucleation and processing .
the tissue then spends a period of days in storage at the eye bank before implantation in the recipient eye .
currently all dsaek donor tissue is prepared by individual surgeons in ontario at the site and time of transplantation , as precut dsaek tissue is not available .
it is our hypothesis that a greater period of time spent in storage prior to processing results in a greater loss of tissue viability and concordantly leads to a higher rate of detachment .
additionally , it is hypothesized that a higher endothelial cell count indicates better tissue function and results in a lower detachment rate
. the primary aim of our investigation is to determine whether these factors play a predictive role in tissue detachment in one surgeon 's practice .
data on donor tissue and procedure outcome were collected through a retrospective chart review of all patients in one academic surgeon 's practice at hotel dieu hospital in kingston , ontario .
the investigation included all of the senior author 's dsaek patients from april 1 , 2007 until march 30 , 2010 .
for all procedures the surgeon cut the donor tissue minutes prior to implantation in the patient .
no major problems occurred in preparing the tissue that might have contributed to dsaek button detachment .
four venting incisions were used in all patients , and interface fluid was drained via these incisions in all patients until no further fluid could be drained .
all patients had a complete fill of air in their anterior chambers for 15 minutes after the drainage of fluid from the venting incisions , and about 50% of the air was removed just prior to concluding each case , to ensure no papillary block developed .
all patients were kept in the recovery area , lying flat for 1 hour postoperatively .
all patients were routine cases undergoing dsaek for fuchs ' endothelial dystrophy or pseudophakic bullous keratopathy .
data on length of time between donor death and tissue procurement , procurement and processing , and time spent in storage were taken from the eye bank reports that accompany the donor tissue .
a total of 71 procedures were performed during the period of study , with 10 resulting in postoperative tissue detachment .
duration of time spent between enucleation , processing , and implantation , as well as endothelial cell count for the detachment and nondetachment groups are summarized in table 1 .
the time spent in each phase of processing was compared between the detachment and nondetachment group using a paired student 's t - test .
this showed no statistically significant difference between the two groups , with the p values reported in table 1 .
endothelial cell counts of the two groups were similarly compared using a paired student 's t - test , again showing no statistically significant difference between the 2 groups .
as demonstrated by our results , there was no statistically significant difference in the storage and processing times between the detachment and nondetachment groups .
this suggests that slight variations in donor tissue processing and storage times do not result in a higher incidence of dsaek graft dislocation .
this of course would apply only to this surgeon 's practice , but may warrant further investigation .
also , it would only include intraoperatively prepared donor tissue and not precut tissue , prepared by the eye bank .
however , dapena et al . described success with a range of ages of precut tissue , suggesting that this result may apply to precut tissue as well .
they did not , however , make a direct comparison between a population of successful implantations and graft failures .
additionally , the use of surgeon - cut tissue has not been shown to have a different incidence of graft dislocation as compared to precut tissue [ 11 , 12 ] .
endothelial cell count was also found not to be significantly different between the two groups , within the population of donor tissue available from the eye bank .
contrary to our initial expectation , the average cell count was actually slightly higher in the detachment group than in the nondetachment group , though this did not reach statistical significance .
the main limitation to this study is its limited scope , including only the practice of one surgeon .
neither length of processing time nor endothelial cell count appears to be significant predictors of graft dislocation in dsaek procedures in one surgeon 's practice .
this suggests that in kingston , all donor tissue from the eye bank being cut by the surgeon at the time of surgery has an equal chance of being successfully implanted , with the determinant of procedural success lying in the technique of the attending surgeon . a future direction for
study could include various surgeons looking at their dislocation rates to see if this is the case in general , or that it was an isolated finding in one surgeon 's practice .
 
 purpose . to determine whether the rate of graft detachment in patients undergoing the dsaek procedure is influenced by the time elapsed between donor death and tissue implantation 
 . methods . data on procedure outcome and donor tissue for patients undergoing the dsaek procedure were reviewed . 
 data on time elapsed between harvest , processing , storage , and implantation of the tissue , as well as donor tissue endothelial cell count were obtained from reports made available from the eye bank of canada . 
 the adverse outcome of interest was graft detachment . 
 results . 
 71 cases were reviewed , with 14% resulting in detachment . 
 the following time periods were compared between detachment and nondetachment groups : donor death to enucleation ; enucleation to processing ; duration of storage at the eye bank to implantation . 
 no statistically significant differences were found ( student 's t - test , p > 0.05 ) . 
 endothelial cell counts of donor tissue were compared between the two groups , and no statistically significant difference was found ( student 's t - test , p > 0.05 ) . conclusion . 
 the range of processing times and endothelial cell counts in donor tissue available from the eye bank did not predict a change in the rate of graft dislocation in one surgeon 's practice . 
1. Introduction
2. Methods
3. Results
4. Discussion