Patients with glaucoma drainage devices (GDDs) have a high rate of graft failure after endothelial keratoplasty (DSEK). 1-2 The mechanism of this increased risk is unknown, but one common hypothesis states that mechanical trauma to the corneal graft by a GDD in the anterior chamber may increase the rate of failure. In this retrospective chart review of 85 eyes, the authors investigate the hypothesis that anterior chamber (AC) GDD may be associated with higher rates of DSEK graft failure than that of pars plana (PP) GDD due to mechanical trauma to the graft. The study found that patients with past or concurrent AC shunt experienced graft dislocation at a rate of 37.7%, which was not significantly higher than the rate graft dislocation in the PP shunt group (29.2%) (P = 0.56). When taking into account the longer follow-up time for the PP shunt group, there was no significant difference between the rates of secondary graft failure (SGF) for eyes with AC shunts 18.9% and eyes with PP shunts 41.7% (log-rank test P = 0.51).
This study by Kang et al., which is the first to compare DSEK outcomes in patients with previous or concurrent AC or PP GDD, demonstrates no association between the rate of DSEK graft failure and GDD placement. However, it is important to note that this study has a small sample size is retrospective and thus not randomized. There are also some significant differences between the comparison groups. The follow-up time was significantly different between these groups with a median follow-up of 41.9 months in the PP shunt group compared to 16.4 months in the AC shunt group (P = 0.001). Furthermore, a much higher proportion of the PP shunt group were concurrent revisions (43.8% versus 18.9%) and concurrent vitrectomy (47.9% versus 5.4%) compared to the AC shunt group, with many of the eyes in the PP shunt group having had a previous AC shunt. Further research, including prospective studies and larger retrospective studies, is required to elucidate the mechanism of DSEK graft failure in eyes with GDDs.