EyeWorld India June 2015 Issue

29 Corneal lamellar surgical procedures June 2015 EWAP SECONDARY FEATURE have had long-standing Fuchs’ and scarring due to the years of swelling, full-thickness scars, perforated or infected ulcers, and bacterial or fungal keratitis that threatens the integrity of the eye. Additionally, eyes with PKs performed 20–30 years ago often develop severe astigmatism from wound ectasia. When these PKs eventually fail, repeat PKs may do a better job than EKs in improving astigmatism and reducing the patient’s dependence on rigid contact lenses. Challenges with PK The biggest challenges with PK remain the delay in visual recovery and the complications associated with full-thickness sutures. These include broken or infected sutures, high postoperative astigmatism, and late-onset traumatic graft ruptures. “There’s no question that endothelial keratoplasties have much more rapid visual rehabilitation, and overall, the quality of their vision is better than with penetrating keratoplasty,” Dr. Mannis said. DSEK patients usually reach their visual goals in 1–3 months, whereas PK patients reach their visual goal at 6–12 months. The shorter visual recovery time with DSEK is a huge advantage, especially for an elderly patient, Dr. Mannis said. High postop corneal astigmatism after PK is also an issue, largely because it is dependent on the healing process of the patient as much as the skill of the surgeon, he added. Dr. Mannis finds that patients who have had a PK in 1 eye and DSEK in the other almost routinely prefer the DSEK eye, even if the two eyes have comparable visual acuity. A potentially devastating complication following PK is traumatic graft rupture, according to Dr. Lee. “[It] is a particularly devastating complication that I see several times a year where a traumatic injury blinds a PK patient from a corneal graft wound rupture and expulsion of ocular contents,” he said. “These issues do not occur with EK procedures and thus represent the major reason why EK has become so popular across the globe.” Concerns over graft survival Although the majority of full-thickness transplants are successful, graft failure due to immune rejection or endothelial decompensation remain major issues. Many donor and recipient risk factors can contribute to these outcomes. On the recipient side, anything that affects the ocular surface adversely affects the success rate of transplants, Dr. Rapuano said, including ocular surface disease, severe dry eye, severe blepharitis, and lid problems. Glaucoma is also one of the biggest risk factors for graft failure, he said, because it contributes to endothelial decompensation, and deep stromal vascularization has been linked to graft rejection. The donor risk factors for graft failure, however, are less clear. There has long been an age bias in graft selection—physicians tend to prefer younger corneas and as a result, many eye banks set an upper age limit of 65 years. The Cornea Donor Study (CDS) helped to eliminate some of that age bias by showing that older corneas (aged 66 to 75 years) had survival rates comparable to younger corneas (12 to 65 years). The CDS data helped to alleviate concerns over whether there will be an adequate supply of donor cornea tissue as the population ages, but more research is needed to determine what donor risk factors are relevant for graft survival. The future of PK The physicians agreed that strategies to promote faster and stronger wound healing after PK would be a tremendous advancement in the procedure. Faster wound healing would mean that sutures could be removed earlier without fear of wound dehiscence, and visual recovery would be more rapid and predictable. “If we had a glue that we could use to secure corneal transplants, without all the sutures and the suture-related problems, that might be something that would improve full-thickness transplant care,” Dr. Rapuano said. Using a femtosecond laser to create the PK wound is one technique that could make strides in this direction. “Femtosecond PK could provide a stronger PK wound and allow for a more stable wound with the potential for earlier suture removal and faster visual recovery,” Dr. Lee said. “Unfortunately, the economics of femtosecond lasers, the decreased surgical efficiency, and the similarities in outcomes to PK with corneal trephines have prevented the technology from becoming more popular.” “I think the femtosecond laser is an interesting idea,” Dr. Rapuano said. “It’s not very practical and didn’t show significant improvement in clinical results, but there may be innovations in the future that show improved clinical results.” The future of PK may also hinge on the evolution of deep anterior lamellar keratoplasty (DALK). In contrast to endothelial keratoplasty, DALK has had little impact on the indications for PK. Of the nearly 50,000 corneal transplant procedures performed in the U.S. in 2013, nearly half were EKs, while fewer than 1,000 were DALKs. “There are newer techniques evolving that will perhaps make DALK more reliably effective than it is right now, but it’s still in a tremendous state of evolution,” Dr. Mannis said. “DALK has traditionally been more popular internationally compared to within the U.S.,” Dr. Lee said. “I think the U.S. will see an increased trend toward DALK for the surgical treatment of anterior corneal conditions like keratoconus and anterior corneal dystrophies in the future as we learn more about DALK from our international colleagues.” Regardless of refinements of lamellar techniques, there will always be a need for PK procedures, even if it is small. “I see it still having a significant place in the practice of cornea because not everyone’s a good candidate for an anterior procedure or a posterior procedure,” Dr. Rapuano said. “There are some training programs that are only doing both of those and not doing any PKs, and I think that doesn’t provide full-service corneal care.” EWAP Editors’ note: Drs. Lee, Mannis, and Rapuano have no financial interests related to their comments. Contact information Lee: lee0003@aol.com Mannis: mjmannis@ucdavis.edu Rapuano: cjrapuano@willseye.org