Long-term incidence of ectasia rare, surgeon says

LONDON — If a patient is going to develop keratectasia after LASIK, it will usually present within 6 to 20 months after surgery, said one ophthalmologist speaking here.

David Gartry, MD, FRCS, FRCOphth, noted the rates of ectasia range from one in 500 up to one in 2,500, and surgeons should be able to identify those at highest risk of its development. He spoke here on the complications of refractive surgery and the likelihood of ectasia development at the Moorfields Bicentenary scientific meeting.

“Risk factors include patients with greater than –8 D, an abnormal cornea preoperatively, a residual stromal bed of less than 250 µm and low preop pachymetry,” he said.

A meta-analysis of 21 published papers dealing with the incidence of keratectasia showed a majority of patients had a best corrected visual acuity of 6/7.5 or worse, 1.25 D of astigmatism or more and a residual myopia of more than 2 D. The residual corneal bed for these patients was less than 400 µm, he said. In addition, he recommended surgeons keep ablation depths to no more than 80 µm.

He said in his own practice he has had three cases of ectasia in more than 8,500 refractive surgeries. All three patients were asymmetric although each had undergone bilateral surgery. In one case, a 39-year-old woman underwent bilateral LASIK in 2001. Her initial error was –8 D/-0.75 x 175, he said. Her pachymetry preoperatively showed 520 µm. The ablation depth was 84 µm. Her residual stromal bed was 276 µm. “So why, 3 years later, did she develop ectasia in one eye but not in the fellow eye?” he asked. While he cannot answer his own question, he advised surgeons presented with patients who do not fall into his “safe” range to be offered the option of undergoing epi-LASIK or LASEK instead.

To manage the complication, Dr. Gartry said he uses spectacles, contact lenses or Intacs (although he said the results for Intacs are “unreliable”), reduces IOP or sutures the flap edge. In some cases, corneal grafting may be necessary. He estimated about 10% to 30% of patients who develop ectasia will require grafting.

“LASIK is still an excellent procedure for low myopes,” he said. “An epidemic of ectasia is unlikely.”

The European Society of Cataract and Refractive Surgeons has created a Web site to collect information about the rates and incidence of ectasia. It can be found at http://www.escrs.org/Corneal_Ectasia.asp, Dr. Gartry said.

He further advised surgeons to avoid advertising complication rates, as some are now doing in the United States and elsewhere. “Quoting a complication rate of 0.1% is useless,” Dr. Gartry said. “You have to break it down for the patient.” For instance, an overall dry eye complication rate of 25% is not uncommon, but errors that are mechanical in nature, such as buttonholes, occur in one in 1,000, and infection may occur in “one in 7,000 or 8,000,” he said.