Results from the prospective, multicenter, randomized, controlled Dutch Lamellar Corneal Transplantation Study support performing deep anterior lamellar keratoplasty instead of penetrating keratoplasty in eyes needing corneal transplantation for stromal pathology not affecting the endothelium.
Orlando, FL-Results from the prospective, multicenter, randomized, controlled Dutch Lamellar Corneal Transplantation Study (DLCTS) support performing deep anterior lamellar keratoplasty (DALK) instead of penetrating keratoplasty (PK) in eyes needing corneal transplantation for stromal pathology not affecting the endothelium, said Rudy M.M.A. Nuijts, MD, PhD, at Cornea 2011: Controversies and Consensus.
"Between 1997 and 2008, about 25% of eyes in The Netherlands needing corneal transplantation would be considered eligible for DALK," said Dr. Nuijts, associate professor of ophthalmology, Academic Hospital Maastricht, The Netherlands. "Yet, only a very small proportion of these potential candidates underwent the partial-thickness procedure because DALK is challenging surgery."
"However, DALK has the advantage of avoiding immunological rejection, and as demonstrated in the DLCTS, it can provide visual outcomes matching PK with significantly less endothelial cell loss if it can be performed without perforating Descemet's membrane," Dr. Nuijts said. "Therefore, I believe it is time to convert from PK to DALK."
He explained that optimizing visual outcomes after DALK depends on deep dissection at the level of Descemet's membrane. However, the number of technique modifications that have been introduced for exposing Descemet's membrane as well as the DLCTS data speak to the difficulty of this step. In the DLCTS, microperforation of Descemet's membrane occurred in 32% of 28 DALK eyes, and in 14% of eyes, it was not possible to achieve a big bubble. Overall, 18% of planned DALK cases needed to be converted to PK.
Results from the DLCTS also showed that if Descemet's membrane is perforated during the surgery, the advantage of DALK for preserving the endothelium is lost. Although the endothelial cell loss rate at 12 months was lower after DALK than PK, 19% versus 28%, the difference between groups was not statistically significant. Once the 32% of DALK eyes with an intraoperative microperforation of Descemet's membrane were excluded, the endothelial cell loss rate in the remaining DALK cases was significantly lower in the DALK versus PK group, 12.9% versus 28%.
"It is important to recognize that the DLCTS was a multicenter study and not all of the surgeons involved were very experienced with DALK," Dr. Nuijts said.
The DLCTS enrolled 56 eyes that were randomly assigned 1:1 to undergo DALK or PK. The two groups were well matched preoperatively for best spectacle-corrected visual acuity, SE, refractive and topographic astigmatism, and contrast sensitivity, and in both groups, the majority of eyes had keratoconus (~54%).
Dr. Nuijts said that early visual outcomes were significantly better in the PK group. However, at 12 months after surgery, best-corrected visual acuity (BCVA) was only about 1 line better for the PK eyes, and BCVA continued to improve in both groups thereafter, so that by 24 months as well as at 3 years, mean BCVA was the same in the two groups.
The 12-month refractive data showed no difference between eyes that underwent DALK versus PK in mean SE, and there were also no significant differences between groups in refractive cylinder or topographic astigmatism.
Quality of vision was evaluated by measuring straylight (C-Quant, Oculus) and contrast sensitivity was tested with Pelli-Robson charts. Data from follow-up at 3, 6, 12, and 24 months showed no significant difference between groups in either endpoint, and there was a significant improvement from baseline in contrast sensitivity in both groups. From the patient's perspective, the two procedures were associated with similar, clinically relevant improvements in vision-related quality of life based on changes in NEI VFQ-25 scores.
There were no endothelial rejections in the DALK group and epithelial rejection occurred in a single eye.
"These results from the DLCTS compare nicely with the findings from a recently published metaanalysis from the American Academy of Ophthalmology that showed no differences between DALK and PK in visual acuity and refractive outcomes but an advantage of DALK for minimizing endothelial cell loss [Ophthalmology 2011;118:209-218]," Dr. Nuijts said.
He also reviewed a 12-month cost analysis of DALK versus PK that was undertaken based on the DLCTS data. While the results showed DALK is the more costly procedure, Dr. Nuijts suggested that over the long term, anticipating a lower rate of future graft failures and improvements to reduce the intraoperative perforation rate, cost-effectiveness would favor DALK [Am J Ophthalmol 2011;151:449-459].
Rudy M.M.A. Nuijts, MD, PhD E-mail: email@example.com
Dr. Nuijts did not indicate any financial interest in the subject matter.