Complications, interventions reduce graft survival after PK in Singapore study

Findings from the Singapore Corneal Transplant Study support deep anterior lamellar keratoplasty and endothelial keratoplasty as safe alternatives to PK.

Donald T.H. Tan

Postoperative complications and interventional procedures markedly diminished long-term graft survival rates after penetrating keratoplasty in a Singapore population, according to a large study.

The results underscored the predominance of postoperative risk factors in affecting graft survival, the study authors said.

“The most significant finding was that postoperative risk factors may play as important a role as preoperative factors or intraoperative surgical factors, with regards to graft survival,” Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, OSN Asia-Pacific Edition Board Member and corresponding author, said in an email interview.

Of 13 identified risk factors that significantly affected graft outcome, eight were postoperative events such as recurrence of primary disease, graft rejection, infection and repeat corneal surgery, Dr. Tan said.

However, preoperative assessment and management of pre-existing pathologies are critical in distinguishing low-risk grafts from high-risk grafts, he said.

“Glaucoma needs appropriate management to ensure that IOP is adequately controlled before proceeding with PK,” Dr. Tan said. “Inflammation needs to be controlled, and the ocular surface needs to be stabilized optimally prior to surgery.”

The study was published in the American Journal of Ophthalmology.

Patients and protocols

The prospective analysis included data from 901 PK procedures performed in the Singapore Corneal Transplant Study, an ongoing cohort analysis of more than 2,750 corneal transplant procedures undertaken at one center in Singapore since 1991.

The cohort included only full-thickness corneal transplantations; all other transplantation methods were excluded. One graft per patient was selected randomly to ensure statistical accuracy.

Univariate and multivariate analyses were undertaken to determine predictive factors for postoperative graft failure. Hazard ratios were calculated for preoperative, intraoperative, donor and postoperative risk factors.

Investigators identified potential postoperative risk factors for limited graft survival; these included nine types of graft complications and eight postoperative surgical or laser procedures.

Preoperative and intraoperative risk factors were combined with postoperative factors to provide a thorough statistical model for final analysis.

Complications, graft survival

According to the study data, the most common postoperative complications were glaucoma or elevated IOP (20.7%), allograft rejection (18.2%) and epithelial problems (15.6%). Primary graft failure was identified in 13 eyes (1.4%). Late graft failure was identified in 9.4% of eyes.

The most commonly performed procedures after corneal transplantation were glaucoma surgery (7.7%), repeat grafting (7.3%) and graft re-suturing (5.7%).

Graft survival rates for eyes without postoperative risk factors were 96.4% at 1 year, 90.8% at 3 years, 87.7% at 5 years and 85.3% at 10 years.

Survival rates for eyes with at least one risk factor were 78.8% at 1 year, 58.6% at 3 years, 48% at 5 years and 34.2% at 10 years.

Overall, the presence of one or more postoperative risk factors significantly reduced graft survival (P < .001).

The most significant postoperative predictors for graft failure were graft rejection, microbial keratitis, endophthalmitis, primary disease recurrence, wound dehiscence, lid surgery, glaucoma surgery and repeat grafting.

The most significant preoperative and intraoperative predictors for failure were female gender, graft size smaller than 7 mm and larger than 9 mm, primary diagnosis, preoperative inflammation and existing perforation, the authors reported.

Surgeons should inform patients about the importance of postoperative examination after PK, Dr. Tan said.

“As such, corneal surgeons must inform corneal transplant patients that postoperative follow-ups are very important to ensure their grafts stay clear, and to identify and treat any postoperative complications at an earlier stage,” Dr. Tan said. “Postoperatively, particular attention needs to be paid to prevent ocular surface complications as well as infection. High-risk eyes need to be on long-term topical steroids and/or systemic immunosuppression to prevent rejection and graft failure.”

Viable alternatives to PK

The findings also supported a shift away from PK toward selective deep anterior lamellar keratoplasty in disorders that spare the endothelium, such as keratoconus and corneal stromal dystrophies, and endothelial keratoplasty in disorders affecting primarily the endothelium, such as Fuchs’ dystrophy, Dr. Tan said.

Performing anterior lamellar keratoplasty in lieu of PK may mitigate the ongoing global shortage of suitable donor corneas in two ways, Dr. Tan said.

“If endothelial rejection is avoided by performing anterior lamellar keratoplasty instead of conventional penetrating keratoplasty, not only will there be less graft failures, but more donor tissue will now be able to be used, as donors with suboptimal endothelial cell status can be used for ALK patients, thus increasing the total amount of corneas available,” he said. – by Matt Hasson

Reference:

• Anshu A, Lim LS, Htoon HM, Tan DTH. Postoperative risk factors influencing corneal graft survival in the Singapore Corneal Transplant Study. Am J Ophthalmol. 2011;151(3):442-448.

• Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, can be reached at Corneal and External Eye Disease Service, Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore 168751; 65-6227-7255; fax: 65-6323-1903; email: snecdt@pacific.net.sg.
• Disclosure: Dr. Tan has no relevant financial disclosures.

This paper reports in detail on the postoperative risk factors after corneal graft. This is a large study of more than 900 eyes and patients with at least 5 years’ follow-up. Preoperative and intraoperative risk factors in this group of Singaporean patients were reported in 2008.

This comprehensive ongoing study with detailed statistical analyses showed the most common postoperative risk factor for graft rejection was microbial keratitis, followed by endophthalmitis and herpes simplex activation. Raised IOP, disease recurrence and allograft rejection were also significant.

Postoperative events requiring active treatment were glaucoma (21%), rejection (18%), epithelial problems (15%), graft failure (9%), cataracts (4%), microbial keratitis (4%) and wound dehiscence (4%). Secondary surgeries required were glaucoma, repeat graft and resuturing (each around 7%) along with cataract and refractive surgery (both near 4%).

When no risk factors were evident, the likely survival rates at 1 and 5 years were 96% and 88%, respectively. When risk factors were present, these survival rates dropped to 78% and 48%.

– Noel A. Alpins, FRACO, FRCOphth, FACS
OSN Asia-Pacific Editorial Board Member
Disclosure: Dr. Alpins has no relevant financial disclosures.