PBK in the setting of ACIOL presents a surgical dilemma for the cornea surgeon.
The decision regarding the optimal surgical management consists of two main components: first, whether to retain the ACIOL or to replace it with a sutured posterior chamber IOL, and second, to evaluate which type of EK is more suitable in this specific setting and would result in a better outcome.
On the one hand, retention of the ACIOL and coping only with the decompensated cornea is an easier and quicker procedure that could be performed under local anesthesia. However, ACIOL retention could cause a higher rate of postoperative EC loss and graft failure (14). As previously mentioned, the DMEK graft needs to be unfolded when inserted into the anterior chamber, unlike the DSAEK graft which is inserted already spread open. The presence of ACIOL makes this process more challenging and might cause excessive endothelial loss and higher rate of graft detachment with lower graft survival rate (15). Hence, in eyes with ACIOL retention, DSAEK might have a better outcome.
Tannan et al. compared ACIOL retention and DSAEK with ACIOL exchange and DSAEK and found no difference in the incidence of graft rejection and primary or secondary graft failure (13). The question remaining unanswered is whether ACIOL exchange combined with DMEK results in better outcomes regarding graft survival, intraoperative and postoperative complications, and visual outcome compared with ACIOL retention and DSAEK.
Concerning graft survival, we found a significantly higher rates of graft failure (both primary and secondary) in the “DSAEK and ACIOL retention” group, compared to the “DMEK and ACIOL exchange” group, where ACIOL was removed and a new IOL fixated to the sclera. Since previous publications comparing primary DMEK to primary DSAEK have established that there is no significant difference in the ECD loss as a result of the procedure itself (1), the higher rate of secondary graft failure could be related to the retention of the ACIOL rather than to a different EK techniques.
Ang et al (3) showed that in eyes after DSAEK with retained ACIOLs, the EC loss three years postoperatively was significantly higher compared with eyes with posterior chamber IOL. Although ECD was not documented during follow-up time in our study, secondary failure is the clinical result of significant ECD loss (16,17).
With these findings considered, we presume that the higher rate of secondary graft failure was a result of the retention of the ACIOL. Therefore, in younger patients with otherwise healthy eyes, we suggest considering ACIOL removal and fixation of the posterior chamber IOL rather than performing DSAEK surgery with retention of the ACIOL.
DMEK combined with ACIOL exchange and trans-scleral fixation is a more complicated procedure than DMEK or DSAEK alone as previously reported (18). Nevertheless, there was no statistically significant difference in primary graft failure, rebubble rate, or BCVA six months postoperatively between the groups.
The main disadvantage of DMEK with ACIOL exchange is a higher rate of complications compared with DSAEK and ACIOL retention in the immediate postoperative time and during the first three months after surgery. It has been reported that EK combined with ACIOL exchange is associated with a higher complication rate. In the mentioned above study by Tannan et al (19), it was reported that postoperative complications in which surgical or medical interventions were required, were more common in the ACIOL exchange group. This finding suggests that the higher complication rate in the “DMEK and ACIOL exchange” group in our study is a result of the removal of ACIOL and scleral fixation of the new IOL.
Considering the aforementioned assumptions that the ACIOL should be removed and a new IOL re-fixated and that the probable cause of the higher rate of complications is the process of IOL exchange itself, we now reach the final step in our pursuit of the preferred management of PBK in the setting of ACIOL, examining the type of EK. As mentioned above, the advantages of DMEK over DSAEK are widely reported(5–7). It is also known that in the setting of PBK the overall graft survival with either technique is lower than in other EK indications such as Fuchs’ endothelial dystrophy. Nevertheless, graft survival after DMEK remains higher compared to DSAEK (20). As with other surgeries, we believe that “practice makes perfect” and since DMEK is a more challenging and complicated procedure, the impact of an experienced and skilled surgeons would be greater, resulting in better visual outcomes.
When assessing the patient prior to surgery, several parameters should be addressed before deciding on the type of procedure; age and presumable life expectancy, functional state, and ability to undergo general anesthesia or tolerate the discomfort of a longer procedure under local anesthesia. A younger patient with a relatively long lifespan is the most suitable candidate for ACIOL exchange with DMEK procedure, which provides a longer graft survival and probably improved visual outcome. Nonetheless, an older patient whose well-being is satisfying, can also benefit from this procedure, although longer and more complicated. Most importantly, these issues should be initially discussed with the patient. The patient should be presented with the higher risk of complications in the DMEK and ACIOL exchange procedure versus the higher rate of corneal graft failure in the DSAEK and ACIOL retention procedure. Above all, the procedure performed should be the one the surgeon is most comfortable with, in adherence to the principle of 'primum non nocere'.
Another matter to consider when approaching a decision regarding patients with ACIOL and PBK is the visual potential. Previous studies show that the visual improvement following these procedures, which are complicated to begin with, is limited. This finding coincides with the BCVA results in this study (4,18).
Our study has several limitations. First, its retrospective nature and probable residual confounders. Second, the possible variability between surgeons in the different medical centers, although this was regarded in the statistical analysis. Third, the lack of endothelial cell count and the relatively small number of patients in each group.
In summary, ACIOL exchange combined with trans-scleral fixation of a posterior chamber IOL and DMEK for the treatment of PBK is a more complex procedure. Nevertheless, the higher rates of graft failure and the need for second keratoplasty with retainment of ACIOL and DSAEK, might suggest that in this specific setting, ACIOL exchange with DMEK would provide a better alternative, especially in younger patients and eyes with poorly positioned ACIOL.