Reduced need for repeat PK

Better EK, prosthetics, outcomes could cut need for full-thickness re-grafts

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Donald Tan MD
Steadily improving outcomes for treating failed penetrating keratoplasty (PK) grafts with endothelial keratoplasty (EK) and corneal prosthetic implants could reduce the need for repeating PK, Donald Tan MD told the American Academy of Ophthalmology 2017 Annual Meeting in New Orleans, USA. “As the learning curve for DSAEK, and now DMEK, allows us to reduce complications and rejection rates of repeat grafting, it is likely that less repeat PKs will be performed,” said Dr Tan, of the Singapore National Eye Centre. Singapore registry data show that long-term graft survival rates for PK vary dramatically by indication, with repeat PK among the worst (Tan et al, Ophthalmology 2008). In fact, at about 70%, PKs generally have about the same 10-year graft survival rates as kidney transplants, while high-risk PKs, including all repeat PKs, are only about 40% – worse than liver transplants, according to another study (Waldock A, Cook SD. BJO 2000;84:813-815). “This is rather depressing,” Dr Tan said. But are the alternatives better? The evidence is growing stronger, Dr Tan said. Reported graft survival rates for Descemet’s stripping automated EK (DSAEK) after failed PK run as high as 96% at four years for patients without glaucoma (Anshu A, Price MO, Price FW. Ophthalmol 2011:18:2155-2160). Similarly, a study by Dr Tan and colleagues found an 86.5% PK-EK survival rate compared with 51.3% for PK-PK at five years (Ang et al. AJO 2014;158:1221-1227). “For us, EK was far superior,” Dr Tan said. However, Australian registry data suggest the opposite, with repeat PK graft survival rates significantly higher than PK-EK for keratoconus and pseudophakic bullous keratopathy patients – though EK failure rates were much higher for inexperienced surgeons, suggesting learning curve is a factor, Dr Tan said (Keane MC et al. BJO 2016;0:1-7). Looking down the road, Descemet’s membrane EK (DMEK) may further improve graft survival after failed PK, though this procedure, too, may be more challenging in post-PK eyes. The Boston KPro 1 prosthesis success rate runs around 60% out to seven years (Aldave JA et al. Ophthalmol 2012; 119:1530-1538) and shows success rates similar to DSAEK out to five years (Ahmad et al. Ophthalmology 2016). “For severe PK failures with total stromal opacification, the Boston Type 1 KPro now appears to be a viable alternative to repeat PKs, with improved intermediate-term survival rates,” Dr Tan said. However, additional follow-up is needed to determine how long-term success rates compare for the KPro versus EK surgery, he added.