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Refractive stability, visual acuity sustained 16 years after PRK
Glare and halos diminished over the follow-up period, and all patients said they would undergo the procedure again.
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PRK for up to 7 D of myopia resulted in stable visual acuity and refraction and minimal optical symptoms at 16 years, a study found.
The study is believed to be the longest follow-up analysis of PRK for mild to moderate myopia, the study authors said.
“This study demonstrates the potential long-term outcomes and results of one treatment after 16 years,” Marc B. Guerin, MD, MRCOphth, said in an email interview. “Re-treatments were excluded so we could ascertain exactly how long only one treatment would last. The problem, of course, with any study of this duration of follow-up is that patients disappear, and thus the attrition rate is unfortunately high.”
Marc B. Guerin
Long-term follow-up data aided physicians in evaluating treatment options, obtaining informed consent and managing patient expectations, Guerin said.
The study was published in the Journal of Cataract and Refractive Surgery.
Patients and parameters
The cohort study included 120 eyes of 80 patients who underwent PRK at one center in Ireland in 1992 and 1993; 39 eyes of 23 patients were followed for 16 years. Mean patient age at the time of surgery was 32.5 years.
“[Patient selection and patient age] were probably quite significant, as the average age was quite high at 32.5 years old, and the highest refractive error was only moderate at –7.25 D,” Guerin said. “Thus, the issue of regression and the need for re-treatments was lessened.”
Preoperative spherical equivalent ranged from –1.75 D to –7.25 D; mean spherical equivalent was –4.36 D. Astigmatism ranged from 0 D to 1.5 D.
All patients underwent single-step PRK performed with the UV200 excimer laser (Summit Technology). Thirteen patients underwent less than 3 D of myopic correction.
Manifest refraction, uncorrected distance visual acuity, corrected distance visual acuity, slit lamp biomicroscopy, dilated fundoscopy, applanation tonometry and corneal topography were assessed at 16 years. Subjective outcomes such as glare and halos and patient satisfaction were also evaluated.
Outcomes and observations
Study results showed that final uncorrected distance visual acuity was 20/20 or better in 27 eyes and 20/30 or better in 36 eyes. Eight eyes lost one line of corrected distance visual acuity and 16 eyes gained one line; no eye lost two or more lines of corrected distance visual acuity.
Mean spherical equivalent was –0.25 D at 2 years and –0.58 D at 16 years.
Results showed an initial hyperopic shift followed by steep regression over the first 12 months; refraction stabilized in subsequent years.
“A temporary postop hyperopic shift is not unusual in the immediate aftermath of PRK and was even more pronounced with 1992 technology,” Guerin said.
Visible haze was identified in four eyes, and two eyes had developing haze. No eyes had clinical or topographic evidence of ectasia. Six patients reported halos or glare but all symptoms improved. All patients said they would undergo PRK a second time.
Guerin attributed clinical and subjective outcomes to thorough preoperative assessment and patient acceptance of new technology.
“This technology was in its infancy at this point, thus these people were by their nature optimistic, positive and wanted to partake in a new treatment,” Guerin said. “Finally, these patients had only one treatment and most derived huge benefits of convenience.” – by Matt Hasson
Reference:
- Guerin MB, Darcy F, O’Connor J, O’Keeffe M. Excimer laser photorefractive keratectomy for low to moderate myopia using a 5.0 mm treatment zone and no transitional zone: 16-year follow-up. J Cataract Refract Surg. 2012;38(7):1246-1250.
For more information:
- Marc B. Guerin, MD, MRCOphth, can be reached at Moorfields Eye Hospital, 162 City Road, London EC1V 2PD, United Kingdom; 44-75-44-820-977; email: marcbguerin@hotmail.com.
- Disclosure: Guerin has no relevant financial disclosures.
Perspective
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Jorge L. Alió, MD, PhD
The authors report the outcomes of a clinical study and patient satisfaction survey performed on patients treated 16 years prior with PRK for low to moderate myopia with a small optical zone and no transitional area. This is, to the best of my knowledge, the first report on small optical zones after such a long period of time. As reported in previously published papers, the patients, despite the primitive technology used at that moment, did well and were satisfied after such a long follow-up. This paper is in agreement with previous reports about the positive long-term outcomes of LASIK and PRK in low to moderate myopia with initial generations of excimer lasers.
The main message of this report is about refractive stability and patient satisfaction. Despite the optical zones used at that moment being clearly inadequate, the patients did well, and probably neuroadaptation has happened to the disability caused by the small optical area. Some regression was confirmed in those with higher refractive corrections. Once more, the excimer laser has proven to be safe, stable and predictable even in the long term in low to moderate myopia. The endpoint is that surface ablation in the form of PRK has confirmed positively the test of time.
Perspective
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George O. Waring III, MD
The authors report on 39 patients followed for 16 years after a single PRK with the Summit UV200 5-mm diameter ablation and no transition zone or astigmatism correction. It worked. But the information presented is as out-of-date as the surgical technique: no topographic analysis, no aberrometry, no thorough analysis of the subjective questionnaire. The term “safe and effective” is used almost as a cliché, especially when there is no information on quality of vision. Nevertheless, the early technology did reduce the myopia and create “happy patients,” a fact that I can affirm, since I presented the Summit data to the FDA that achieved the first U.S. regulatory approval for excimer laser vision correction surgery.
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