The retreatment flap over epithelial ingrowth

Comparing ingrowth issues with femtosecond created flaps to those made with microkeratomes

Epithelial ingrowth
Source: William Trattler, M.D.

It’s an omnipresent risk of performing a LASIK retreatment—the potential for significant epithelial ingrowth. But can the way the LASIK flap was initially created have ramifications on later development of this all too pervasive problem? That’s what investigators set out to find in a study published in the November 2009 issue of the Journal of Refractive Surgery, according to Francis W. Price Jr., M.D., Price Vision Group, Indianapolis.
“The biggest concern with epithelial ingrowth has been retreatments for which the incidence is tremendously high,” Dr. Price said. “Some have estimated this to be 5%-10%.” Not all LASIK procedures appear to be equal in this regard. “It’s good news that the newer excimer lasers, especially when combined with the femtosecond lasers, seem to have fewer retreatments,” Dr. Price said. However, since practitioners sometimes need to retreat LASIK patients who had undergone the procedure eight or 10 years earlier, Dr. Price thinks that it’s important to understand all of the relative risks.

Retreatment woes

Currently there is no consensus on why retreatments are so prone to epithelial ingrowth. Dr. Price attributes this in part to bad luck or to something about the technique. “Surgeons should be really meticulous with their technique; if they actually implant epithelium then they’re going to get this,” he said. “What usually happens is that there is some kind of trauma or an area where the edge of the flap doesn’t seal down as tightly as we would like and then the epithelium has a track and could start growing.”
As a rule, Dr. Price finds that although the femtosecond lasers are more expensive, they tend to be a bit safer and the complications are easier to deal with than with the microkeratome. But he wanted to see if the same held true for epithelial ingrowth. “I was getting the impression that we had fewer epithelial ingrowth cases with the femtosecond and I thought we should look into that,” Dr. Price said.
Included in the study were 272 retrospective, consecutive retreatments performed over a four-year period. The flap was lifted using the same technique for all eyes included in the study. Of the cases involving a mechanical microkeratome, 132 required retreatment. When investigators looked at epithelial ingrowth they found that 9 of 11 eyes required surgical intervention to remove this from the stromal interface. Meanwhile, when they looked at cases involving flaps initially created by the IntraLase (Abbott Medical Optics, Santa Ana, Calif.), epithelial ingrowth was found in two eyes of one patient of those in the femtosecond group. In neither case was it necessary to use surgery to remove the epithelial ingrowth.

A cut above?

Dr. Price theorizes that the type of cut made by the microkeratome to initially create the flap makes it vulnerable to epithelial ingrowth. “We think that is because whenever you use a microkeratome you have a tapered incision because the blade starts and goes into the tissue at an angle,” he said. “The angle could vary depending upon the microkeratome and then it gets to the dissection bed and stays at that depth. With the femtosecond laser, you basically set the entry angle at whatever you want.”
In most cases with the IntraLase, Dr. Price finds that practitioners use an entry that is close to vertical. “We usually do the entry at about 70 degrees. In our experience that seemed to minimize the tendency of the epithelium to grow back under it,” he said. “I think that it makes a better seal and that makes it harder for the epithelium to get around the corner and go in.” As a result, epithelial ingrowth is less likely to occur.
Dr. Price sees the clinical message as clear cut. “The take-home message is that surgeons are less likely to get epi ingrowth if they use a femtosecond laser,” he said. “It’s another one of the advantages of a femtosecond laser.” There is a caveat here, he stressed. “We can’t speak for all of the lasers because the Ziemer (Ziemer Ophthalmic Systems AG, Port, Switzerland) does a tapered incision kind of like a microkeratome,” Dr. Price said. “We don’t know whether that will have any advantages compared to the microkeratome in regards to the incidence of epithelial ingrowth.”

Editors’ note: Dr. Price has financial interests with Abbott Medical Optics (Santa Ana, Calif.), Alcon (Fort Worth, Texas), and Allergan (Irvine, Calif.).

Contact information

Price: fprice@pricevisiongroup.net