This large retrospective study found that glaucoma surgical intervention is associated with significantly worse graft survival after penetrating keratoplasty and DSAEK, while medical therapy alone is not.
Investigators reviewed the charts of 57 consecutive eyes that underwent penetrating keratoplasty and 156 consecutive eyes that underwent DSAEK stratified into those with no glaucoma treatment, those that received medical therapy only or those that received surgical intervention.
After either procedure, five-year graft survival was excellent in eyes that required no treatment or medical therapy only. However, surgical intervention was associated with a dramatically worse prognosis for graft survival compared to no treatment or medical therapy alone.
They write that the etiology of the association between glaucoma surgery and a high rate of graft failure is probably multifactorial and includes both mechanical and immunological etiologies, including direct trauma from the close proximity of a tube to the endothelium and mechanical trauma associated with the anterior segment manipulations required for placement of a tube.
They hypothesize that glaucoma surgical interventions, irrespective of their timing in the clinical course, may have compromised the protective effect of anterior chamber-associated immune deviation and led to some cases of chronic endothelial rejection that may not have been clinically obvious. If so, this factor, in combination with other mechanical causes of endothelial attrition associated with glaucoma surgery, may have contributed to the high incidence of graft failure.
The authors also note that this study afforded an opportunity to compare the outcomes of penetrating keratoplasty and DSAEK in a similar patient population with the same surgical indication managed by the same set of corneal surgeons and co-managed by the same group of glaucoma specialists.
The five-year graft survival was virtually identical with both procedures in eyes without glaucoma therapy, eyes with medical therapy alone and in eyes with surgical intervention. The similarity of graft survival irrespective of glaucoma therapy status suggests that mechanical factors that may be more favorable for endothelial survival after penetrating keratoplasty are neutralized by immunologic factors that may be more favorable to endothelial survival after DSAEK. It also suggests that concerns about differential survival relative to the glaucoma treatment regimen need not be applicable to procedure selection.
They conclude that patients who have already had surgical intervention or who require a combined keratoplasty and glaucoma procedure must be advised of the guarded prognosis for long-term graft survival.