Lasik offers ‘very effective treatment’ for refractive errors after PK, says US specialist

Ana Hidalgo-Simón MD, PhD
in Gatwick

Stephen S. Lane MD

AN increasing amount of clinical research suggests that Lasik can be performed safely and effectively to correct a wide range of refractive errors in selected patients who have undergone penetrating keratoplasty (PK), according to Stephen S. Lane MD.

“Lasik offers a considerable capability for enhancements and a relatively low risk of scarring. However, it may also cause a weakening of the wound and can potentially induce graft rejection. Predictability is good in some cases but is not fail-safe,” he told a session of the Cornea 2002 meeting. Dr Lane conducted a retrospective study based on the results he recorded with Edward J. Holland MD, University of Cincinnati, US. All surgeries were performed between 1998 and 2000. The review included 33 eyes, of which 76% were keratoconus patients. The mean age of patients was 46 years.
The indications for Lasik were either anisometropia or contact lens intolerance. Patients with irregular astigmatism were excluded. Lasik was typically performed more than one year after PK, and then only after all sutures were removed and topography showed a stable eye.

The surgeons used the VISX Star2 excimer laser, with an optical zone of 6.0 mm. They used the Hansatome microkeratome in 28 eyes and automated corneal shaper in five.
The mean number of months from PK to Lasik was 62, ranging from 10 to 216. Mean refractive error before Lasik was -6.2 D, ranging between -12.75 D and +1.5 D, and the mean cylindrical error was 6.0 D within a range of 1.25 D and 9.5 D.
Flap creation and laser ablation were performed as a one-step procedure. A pilot study indicated that there was no clear difference or advantage in doing otherwise, Dr Lane explained.

The mean follow-up after Lasik is now more than one year. Analysis of these results showed that 69% of eyes achieved a UCVA of 20/40 or better after Lasik, and 88% had a BCVA of 20/40. Some 65% of those saw 20/20.
“We found that our mean reduction in spherical error after Lasik (81%) was much better than our mean reduction in cylinder (65%).
“A comparison of studies looking into this in the literature shows that everybody is much better at taking care of the sphere than the cylinder. This is an important point to consider when you set your expectations for these operations,” he said.
Complications included three cases of diffuse lamellar keratitis (DLK), two of which resolved with topical steroids. There was also one buttonhole flap and one slipped flap requiring suturing. There were no cases of graft rejection.

The surgeons performed five enhancements without any complications. One case could not be lifted and was recut without further complications, Dr Lane reported.
“There are other ways to treat refractive problems following PK, but these are in general very invasive. Lasik has many potential advantages over PRK, including a reduced risk of glare and haze.
“I believe Lasik is a very effective treatment for refractive errors after PK, but is more effective in treating myopia than astigmatism in these patients. And the treatment is very safe,” he said.
Dr Lane also highlighted his concerns regarding the use of Lasik in these patients, noting the potential for weakening or dehiscence of the wound and the potential for graft rejection. He also noted a concern for the unpredictability of the refractive outcome and the possibility of regression.

Based on his clinical experience, he recommended waiting between 10 and 12 months in patients under 40 years before performing Lasik after PK, and 18 to 24 months for those over 50.

He also warned that it might be necessary to recut for enhancements because flaps may be very difficult to lift due to healing of the flap at the graft host interface.
“The ability to achieve good results with Lasik has changed the way I treat PK patients postoperatively. Now I only use interrupted sutures and I hardly ever perform sequential, topographically-guided suture removal.
“Instead, I remove sutures as soon as possible, aiming to perform Lasik around a year after the PK operation. I have reduced significantly the amount of steroids I use during the postoperative period.
“I tell my patients, especially those with keratoconus, that the treatment procedure has two stages — the second one is the Lasik procedure,” Dr Lane said.

Stephen S. Lane MD
University of Minnesota, US
Email: sslane@associatedeyecare.com

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