Take-home message: Researchers explore the efficacy and reliability of laser vision correction for the treatment of residual refractive error after refractive lens exchange.
By Fred Gebhart; Reviewed by Steve Schallhorn, MD
San Diego—Both LASIK and PRK are safe and effective procedures to treat residual refractive error following refractive lens exchange (RLE), according to a multisite, international study.
The study also suggested a preference to perform LASIK for residual hyperopia and PRK for myopia, said senior author Steve Schallhorn, MD.
“This large sample—larger than previous reports—showed that laser vision correction after implantation of a premium IOL is safe and effective and can improve unaided vision,” said Dr. Schallhorn, clinical professor of ophthalmology, University of California San Diego School of Medicine and chief medical director for Optical Express.
LASIK is the preferred procedure for faster visual recovery, as more patients attained 20/20 vision in the early postoperative time period. However, PRK has multiple advantages, including not needing pressure-raising suction for the flap creation. PRK is also a simpler procedure to perform, he noted.
Both LASIK and PRK have similar long-term outcomes and both carry the possibility of dry eye side effect symptoms.
Patients who receive a premium IOL tend to have higher expectations than patients receiving a standard monofocal IOL following cataract surgery, Dr. Schallhorn said.
Goal of emmetropia
Presuming that emmetropia is the target, the closer postoperative refractive error is to zero, and the higher patient satisfaction and the fewer and less intrusive the patient’s visual symptoms.
“Getting to that goal of emmetropia is important and well recognized,” he said. “The real question is how to best achieve it.”
For patients who have residual refractive error, several options have potential. If the refractive error is significant, the IOL can be repositioned or exchanged or a piggyback lens can be implanted. Astigmatic keratotomy may be appropriate if the spherical equivalent is on-target, but there is visually significant astigmatism.
For patients with a relatively modest refractive error—typically within a few diopters—laser vision correction may be more appropriate.
Prior studies have used both PRK and LASIK procedures in smaller populations. Regardless of the procedure selected, patients must meet four basic criteria for laser vision correction following RLE:
- The patient must have a visually significant refractive error.
- The error cannot be large enough to warrant IOL repositioning or exchange.
- The patient must desire improved vision.
- The patient must meet other indications for laser vision correction.
Researchers conducted a retrospective review of patients who underwent laser vision correction following RLE between January 2008 and June 2014 using Optical Express’ electronic medical records.
The study cohort included 661 patients and 893 eyes that underwent LASIK after RLE and 602 patients and 724 eyes that underwent PRK after RLE. The two cohorts were well matched, a mean age of 54 in both groups, and 52% male in the LASIK group versus 53% male in the PRK group. The LASIK group had 49% of left eyes and 51% of right eyes treated compared with 44% left and 56% right in the PRK group.
The preoperative refraction showed a mean sphere of 0.28 ± 1.06 D with a minimum of –3.75 and a maximum of +3.75 D. This improved to +0.03 ± 0.52 D for LASIK and +0.08 ± 0.57 D for PRK (p < 0.001 for both LASIK and PRK). The average time from laser vision correction to last postoperative refraction was 5.4 months.
The mean preoperative cylinder was –1.00 ± 0.67 D with a maximum of –4.5 D. This improved to –0.36 ± 0.37 D for LASIK and –0.43 ± 0.46 D for PRK.
A total of 96% of LASIK patients were within 0.5 D of goal at final refraction compared with 94% of PRK patients.
Patients who had a myopic correction after RLE were more likely to have 20/20 uncorrected distance acuity (UCDA) compared with patients who had a hyperopic correction, 70.8% versus 60.4% (p < 0.001). Treatments that were wavefront guided were more likely to produce 20/20 UCDA, as were LASIK treatments, Dr. Schallhorn said.
“We showed that both LASIK and PRK are safe and effective,” he said.
PRK has some advantages in that the procedure is relatively easy to perform, particularly for surgeons who do not have extensive refractive surgery experience, he noted.
“You would need appropriate training and access to an excimer laser, but this should not be particularly onerous to achieve,” Dr. Schallhorn said. “Being simple and straightforward to perform are important advantages for PRK to enhance the final outcome of a premium IOL.”
At the same time, faster visual recovery and less perioperative discomfort are significant advantages of LASIK. However, long-term outcomes for the two procedures are similar.
Steve Schallhorn, MD
This article was adapted from Dr. Schallhorn’s presentation at the 2015 meeting of the American Society of Cataract and Refractive Surgery. Dr. Schallhorn is chief medical director for Optical Express.