There is no controversy that posterior lamellar keratoplasty is today the gold standard in endothelium transplantation. It has been the procedure of choice because of its advantages over PK, such as higher survival rates and fewer surgery-related complications. Still, most published studies have reported results in moderate- to low-risk conditions, such as pseudophakic bullous keratopathy or Fuchs endothelial dystrophy.6,7 We report 34 eyes with a history of high-risk conditions, such as previous graft failure, anterior chamber IOLs, glaucoma surgery (tube shunt, trabeculectomy, or transscleral cyclodestructive procedures), or any anomaly that may complicate surgery or postoperative evolution. 8.9
Although primary and secondary graft failure are commonly-described DSAEK complications, there is little information regarding these complications in high-risk patients. Lee et al. found primary graft failure to be the third most common DSAEK complication in the reviewed literature, with a range of 0–29% and an average PGF rate of 5% among all published studies, but not considering high-risk patients.7 In patients with previous graft failure, we reported a PGF of 42% and SGF of 14%. Einan et al. reported 50% of graft failure in a group of DSAEK in previous failed PK, similar to our subgroup of patients with prior graft rejection.10 In eyes with previous GDD and DSAEK, Aldave et al. reported a PGF of 8.2% and SGF of 18%.11 Similarly, Kang reported that 35% of patients with previous trabeculectomy and GDD who underwent DSAEK experienced an SGF.12 Our PGF in patients with previous GDD was 53%, with no SGF during the follow-up. Hernstadt et al. reported that GDD patients experienced an initial survival graft rate at 12 months comparable to DSAEK with no GDD. However, graft survival declined significantly, such that the survival rate was 75% by 24 months and 63% by 36 months.13
Providers should exercise additional caution in cases of previous GDD or concomitant GDD. Surgeons must more closely monitor the length of the tube, the angle of insertion, and the tube's location. Also, maintaining air tamponade and the graft attached is more challenging in eyes with previous glaucoma surgery or vitrectomy as it is easier for the injected air to migrate into a vitrectomized posterior chamber or through a fistula. In six cases where an air bubble could not be retained in the anterior chamber, a transfixing suture was passed through the transplanted tissue; two of these cases subsequently failed.
Another relatively frequent complication was graft dislocation. Overall, we reported six cases (17%) of graft dislocation, three of which were successfully treated with air rebubbling or transfixing suture. Some authors report a dislocation rate from 5–20%.6,14,15 Specifically, a rate of 18-35.7% has been reported in patients with GDD,11,1 and of 25% in patients with previous graft rejection.10
The fact that there is a steep learning curve in regard to this type of surgery should be considered when analysing surgical complications like graft detachment. Aldave et al. reported complications in 23 and 13 of the first 100 cases performed by each surgeon (18.0% average) and in 20 of 261 subsequent cases (7.7% average).11 This learning curve must be considered even more in patients with high-risk conditions, for example, cases where a tube must be repositioned or implanted, or a concomitant anterior segment surgery must be performed. Our surgical group was made up of first or second-year fellows assisted by an experienced surgeon. Evidence suggests that poor surgical technique, the use of specific surgical steps that are inherently more traumatic, and excessive tissue handling due to surgeon inexperience are all associated with higher PGF risk. There is also a learning curve in cutting the donor cornea with a microkeratome to produce a lamella graft. It should be noted that in this study, our surgical team prepared the lamella graft for 29 eyes (85.2%).16
Further studies with a higher number of patients and longer follow-up need to be done to support more efficient and effective clinical decision-making. Furthermore, more attention should be made to improving the learning curve in these difficult cases, as this could reduce the high rate of PGF. Our study suggests that high-risk DSAEK presents an elevated percentage of PGF with minimum improvement in BCVA. The most common complication was graft detachment, with a rate similar to other reports in non-high-risk patients. In our series, previous graft failure is a higher risk factor than a GDD.
To summarize, the present study shows anatomic and visual results, survival rates, and complications in high-risk patients who underwent DSAEK in a referral ophthalmological centre. These results can help us understand the limitations and risks of this surgery in this group of patients. We can conclude that adverse outcomes are highly common in high-risk patients who received a DSAEK, especially in those patients for whom a graft previously failed or with a glaucoma drainage device. The most common complication was graft detachment, with a rate similar to other reports in non-high-risk patients. In our study, previous graft failure is a higher risk factor than a GDD. This nature of this study (retrospective) and the lack of comparison does not provide enough evidence to draw conclusions about the difference between high-risk and non-high-risk patients. Further investigations are needed to definitively establish the risk factors, similarities, and differences between high-risk and non-high-risk patients who underwent a DSAEK.