Single-Step Transepithelial Photorefractive Keratectomy Superior to 2-Step Procedure

FI.Eye.#2.AS.1–8–97.A UCLA, Los Angeles, CA. Dr. Robert K. Maloney, M.D.,M.A., Director of Diseases and Surgery of the Cornea at the UCLA Laser Refractive Center at Jules Stein Eye Institute is performing PRK (Photo–Refractive Keratectomy) to patient Yael E. Haffner with the excimer laser that removes microscopic layers of tissue from the surface of the cornea to correct nearsightedness. Photo ^^^. (Photo by Al Seib/Los Angeles Times via Getty Images)
The single-step approach more effectively corrects mild to moderate myopia and myopic astigmatism and has a faster recovery time, a report shows.

A single-step transepithelial photorefractive keratectomy (PRK) approach more effectively corrects mild to moderate myopia and myopic astigmatism, and has a faster recovery time compared with the 2-step phototherapeutic keratectomy (PTK)-PRK procedure, according to findings published in Eye (Lond).

This prospective, randomized, comparative trial was conducted at the TIBA eye center in Egypt. Patients (N=50) with myopia and myopic astigmatism in both eyes were randomized to undergo the 2-step transepithelial PTK-PRK procedure (50 eyes of 25 patients) or a bilateral single-step transepithelial transepithelial PRK procedure (50 eyes of 25 patients). The primary outcomes were visual acuity and manifest refraction and secondary outcomes were epithelial healing, pain, and haze.

The cohorts had a mean age of 25.4±1.9 and 25.1±1.4 years. The ratios of women to men were 17:8 and 16:9, respectively, uncorrected distance visual acuities (UDVA) were 1.03±0.23 and 1.04±0.19 logMAR, corrected distance visual acuities (CDVA) were 0.02±0.006 and 0.02±0.006 logMAR, and manifest spheres were -2.37±0.25 and -2.42±0.18 D, respectively.

At 1 week and 1, 3, and 6 months, UDVA was significantly better among the single-step PRK cohort (P <.001). At 12 months, the both cohorts achieved UDVA of 20/20 (72% vs 36%) and 20/25 or better (92% vs 78%). At 1 week, CDVA was significantly better among the single-step PRK recipients, but was similar between groups thereafter.

The single-step PRK procedure was favored for astigmatic efficacy (P <.001) and manifest sphere (P <.001) outcomes. At 6 months, 78% of the single-step PRK eyes had a postoperative cylinder of 0.25 D or less compared with 32% of PTK-PRK eyes.

The average time to epithelial healing was 3.24±0.43 days in the single-step PRK procedure group and 5.48±0.76 days in the PTK-PRK group (P <.001). The single-step group reported less pain up to postoperative day 7 (P <.001). The proportion of patients reporting no haze at 3 months was similar in the single-step PRK (62%) and PTK-PRK groups (60%).

A significant correlation was observed between the depth of stromal ablation and haze at 3 months (r, 0.48; P <.001) and a correlation was trending toward significance for the depth of epithelial ablation and manifest refraction spherical equivalent at 6 months among the single-step PRK recipients (r, 0.27; P =.054).

No postoperative complications occurred. Limitations of this study included the small sample size and the inability to perform contralateral eye operations.

“Although both … groups showed significant improvement of postoperative refractive outcome parameters (postoperative UDVA, the manifest sphere, cylinder and MRSE at all follow up visits), a faster visual recovery with a better refractive outcome was achieved in the single-step TE-PRK group when compared with the PTK-PRK group,” researchers explain.

This study found that the single-step TE-PRK was also associated with shorter time to epithelial healing and less pain.


Abdel-Radi M, Shehata M, Mostafa MM, Aly MOM. Transepithelial photorefractive keratectomy: a prospective randomized comparative study between the two-step and the single-step techniques. Eye. Published online July 21, 2022. doi:10.1038/s41433-022-02174-4