PRK safe, stable after 12 years

Almost 90% of eyes recalled for 12-year follow-up maintained or improved best corrected visual acuity, the retrospective study found.

Myopic eyes that underwent PRK in the early days of laser corneal refractive surgery have maintained refractive stability and low myopia through 12 years of follow-up, a retrospective study found.

The study also found a high rate of patient satisfaction, despite reports of night vision problems from about 40% of patients.

The results of the study, by Jeremy O’Connor, MRCOphth, Michael O’Keeffe, FRCS, and Patrick I. Condon, FRCS, of Mater Private Hospital, Dublin, Ireland, were published in the Journal of Refractive Surgery. Mr. O’Keeffe is the corresponding author of the study.

Eighty patients (120 eyes) underwent one-step myopic PRK at the Mater hospital during 1992 and 1993. Of that group, 39 patients (65 eyes) were located and agreed to return for a follow-up examination 12 years after surgery. The researchers excluded five patients who had undergone re-treatment, leaving 34 patients (58 eyes) with only the primary PRK treatment for long-term evaluation, the authors said. Patients ranged from 20 to 54 years old.

The researchers performed slit-lamp examination, corneal topography, wavefront aberrometry and specular microscopy and evaluated visual acuity, refraction, corneal haze and complications. They also used a survey to gauge patients’ subjective outcomes and satisfaction.

Refraction/visual acuity

Michael O'Keeffe

Of the 58 eyes studied, 47 (81%) were within ±1 D of emmetropia and 36 (62.1%) were within ±0.5 D of emmetropia after 12 years. Four eyes (7%) were greater than ±2 D from emmetropia.

The authors observed a hyperopic shift in the first 12 months after surgery. However, eyes exhibited refractive stability between 2 and 12 years after surgery. Mean refractive error was +0.06 D at 1 year, –0.27 D at 2 years and –0.58 D at 12 years.

For most patients, corrected visual acuity remained stable or improved; 51 eyes (87.9%) maintained or improved from the preoperative level of best corrected visual acuity. Only seven eyes (12.1%) lost one line of BCVA, and no eyes lost two lines, the study authors said. Regarding efficacy, 39 eyes (67.2%) had uncorrected visual acuity 20/20 or better, and 53 eyes (91.3%) had UCVA of 20/40 or better.

Ten eyes (17.2%) had trace visible corneal haze at 12 years’ follow-up. All but one of those eyes had been corrected for myopia higher than –5 D. The amount of corneal haze had gradually decreased over the 12 years.

Return to the surface

The amount of corneal haze decreased after 12 years.

Image: O'Keeffe M

Mr. O’Keeffe said it is important to review the results of early PRK procedures because interest is returning to surface ablation.

“We’re moving more and more back to the surface of the cornea,” he said in an interview with Ocular Surgery News. “In my practice, 2 years ago it was 90% LASIK, 10% surface [ablation] ... and today I’m doing 70% LASIK and 30% LASEK.”

Patient selection was conservative when these patients underwent PRK.

“The first PRK patients were only 14 or 15 years ago, and this is 12-year follow-up, so at the time PRK was literally just starting out,” he said. “Patient selection was crucial, so we did low to moderate myopes at the time.”

He said having long-term data on those early procedures is important because many “high-volume commercial clinics” today do not carry out appropriate follow-up and quality measurements.

“I think studies like this are absolutely vital for both doctors and patients ... because of the questions that most patients ask any doctor when they come in: ‘What are the long-term effects?’”

Minimal complications

No eyes showed clinical or topographic signs of corneal ectasia. Corneal topography showed no great change in keratometric power or simulated keratometry from preop to 12 years postop, the authors said, noting that direct comparisons were difficult because of changes in topography equipment over the interval.

In response to the questionnaire, 14 patients (41.1%) reported some degree of night vision problems, 11 patients described those symptoms as mild, two as moderate and one as severe. All 14 patients said these symptoms had improved during the 12-year interval. Eight patients reported that they were “uncomfortable” driving at night. Sll patients reported that they would have the procedure again.

For more information:
  • Michael O’Keeffe, FRCS, the corresponding author of this study, can be reached at Mater Private Hospital, Eccles St., Dublin 7, Ireland; 353-1-8858626; fax: 353-1-8858490; e-mail: Neither he nor his fellow authors have a direct financial interest in the surgical procedures discussed in this article.
  • OConnor J, OKeeffe M, Condon P. Twelve-year follow-up of photorefractive keratectomy for low to moderate myopia. J Refract Surg. 2006;22:871-877.
  • Matt Hasson is an OSN Staff Writer who covers all aspects of ophthalmology and focuses on regulatory, legislative and practice management topics.