Take-home: According to recent study results, transepithelial photorefractive keratectomy is a better alternative procedure than other refractive methods when treating myopia that involves epithelium mechanical manipulation.
Seoul, South Korea—Transepithelial photorefractive keratectomy (TransPRK) is a safe and effective alternative to other refractive procedures to treat myopia that involve mechanical manipulation of the epithelium, according to 12-month data from a South Korean prospective study.
This all-laser version of PRK showed similar visual and predictive results compared to LASEK and types of PRK that involve mechanical or alcohol-based removal of epithelium, however, it offered faster operative times, faster healing, less haze, and less postoperative pain than the more conventional and more invasive procedures.
“Transepithelial PRK with the Amaris laser platform is a modified no-touch, continuous single step technique for combined epithelial and stromal ablation,” said Jung Sub Kim, MD, B&VIIT Eye Center, Seoul, Korea. “The Amaris platform removes corneal epithelium with a modified PTK mode, which is different from other surface ablation refractive surgical techniques that use a brush, alcohol and other methods."
The instrument used—the Amaris 750 Hz excimer laser (Schwind eye-tech-solutions, Germany)—has been approved for use in Asia and the European Union, but has not been approved for clinical use in the United States.
TransPRK is the next step in the development of surface manipulation using
The all-laser system combines epithelial ablation and the refractive laser treatment in a single step, which reduces operative time. The no-touch technique is gentler on the eye, which translates into faster healing and faster restoration of visual acuity.
The mean corneal epithelial thickness is 53 µm at the center and 63 µm at the 8-mm periphery, he continued.
The Amaris PTK ablation target is 55 µm centrally and 65 µm at the periphery of the 8-mm ablation zone. The single step ablation not only reduces operative time, but reduces the risk of dehydration between steps that is part of most other refractive surgical techniques.
Examining the study
Dr. Kim and his colleagues treated 381 eyes of 159 patients with a mean age of 27.2 years. The cohort included 68 males and 91 females. The mean preoperative spherical refraction was -4.12 D, the mean cylindrical refraction was -0.63 D, and the corrected visual acuity was 20/20 or better for all patients.
Patients with corneal epithelial pathology, keratoconus, ocular inflammation, glaucoma, or posterior segment pathology were excluded from the study.
All patients received mitomycin-C (0.01% for 10 to 25 seconds), a soft bandage contact lens for 3 to 4 days as needed, topical levofloxacin 4 times daily for 2 weeks, and fluorometholone (0.1%) 6 times daily after epithelial closure, and tapered over 3 to 4 months.
Postoperative pain was assessed by patient report and epithelial healing was evaluated by daily slit-lamp exam until the re-epithelialization was complete. Uncorrected visual acuity, best corrected visual acuity, remaining refractive error, and corneal haze were evaluated at 3 or 4 days, 3 weeks, 2 months, 6 months and 12 months following surgery.
Dr. Kim reported that 95.5% of patients had complete epithelial healing at 3 days postoperatively, and all patients showed complete epithelial healing by 4 days. At 12 months, 4 eyes had evidence of grade 1 haze and 1 eye had grade 2 haze. At 12 months, 99.1% of patients had 20/20 or better uncorrected visual acuity. Nearly all patients showed progressively improving visual acuity from 3 weeks through the 2-month, 6-month and 12-month exams.
Refractive results were excellent and highly predictable. At 12 months, 98.5% of patients were within 0.5 D of the preoperative spherical equivalent target, 96.2% were within 0.5 D of the spherical refraction target and 94.8% were within 0.5 D of the cylindrical refraction target. Results were also extremely stable. Most patients, 97.8%, had a change in spherical equivalent of 0.5 D or less from 2 months postoperatively to 12 months after surgery.
While the outcomes from the Amaris instrument are highly positive, the instrument is not ideal for all patients, Dr. Kim noted. It is less useful in patients with abnormal or uneven epithelial thickness resulting from scarring due to prior procedures or corneal pathology. The study also did not attempt to evaluate high order aberrations or make direct comparisons with other surface ablation techniques.
“This study, like many others around the world, show that transepithelial PRK using the Amaris platform showed very good effectiveness, safety and predictability, faster epithelial healing, and less postoperative pain than we see in the literature for other types of refractive surgery,” Dr. Kim said. “It is a very useful alternative for the patient who wants faster healing and less postoperative pain.”
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