Table 3.
Summary of selected studies on PRK and myopic regression conducted over more than two decades
| Author (Year) | Participant characteristics | Conclusions |
|---|---|---|
| Li et al. (2022) [ 25 ] | Included 45 eyes (25 patients) in the femtosecond LASIK treatment group and 44 eyes (24 patients) in the tPRK treatment group. | Postoperative myopic regression was investigated from 8 to 21 months. When regression occurred, corneal epithelial thickness was significantly increased compared with preoperative values in both treatment groups. When myopic regression subsided three months after steroid therapy, corneal epithelial thickness was significantly decreased compared to values at treatment onset. |
| Shin et al. (2020) [ 26 ] | Ninety-five eyes underwent PRK with a 6.0-mm OZ (n = 40 eyes) or a 6.5-mm OZ (n = 55 eyes). | No significant differences were found in the SEQ of manifest refraction, simulated K value, UCDVA, or regression between 6.0-mm OZ and 6.5-mm OZ over one year post-PRK. The 6.5-mm OZ eyes had a better root mean square of higher-order aberrations, spherical aberration, and Q value measured in the 8.0-mm zone (mean follow-up was 20.71 versus 17.47 months in the 6.0-mm and 6.5-mm OZ group, respectively). |
| Naderi et al. (2018) [ 19 ] | Of 293 eyes of 150 participants who underwent PRK, the numbers of eyes with myopic astigmatism, hyperopic astigmatism, myopia, astigmatism, and hyperopia were 223, 37, 16, 14, and 3, respectively. | The prevalence of regression was higher in women (21.1% in women versus 15.9% in men), in the > 30-year age group (21.4% in > 30 versus 17.4% in < 30-year group), myopic astigmatism (78.1% in myopic astigmatism versus 10.5% in hyperopic astigmatism), and myopia (5.9% in myopia versus 1.3% in hyperopia). The Generalized Estimating Equations of the independent variable of regression after PRK showed that the simulated K value, 5-mm irregularity, and sphere value were significantly related to refractive error regression. For myopic astigmatism, the 5-mm irregularity, simulated K value, and increase in the SEQ increased the likelihood of refractive error regression. |
| Pokroy et al. (2017) [ 20 ] | A total of 9699 consecutive patients (9699 eyes) underwent myopic PRK with mitomycin-C. | The likelihood of retreatment increased significantly with astigmatism ≥ 3.5 D and surgeon factor. tPRK and high astigmatism were associated with increased myopic PRK retreatment rates. |
| Alio et al. (2016) [ 21 ] | Outcomes of PRK for 33 eyes of 33 patients with myopia up to -10.00 D and - 4.50 D of astigmatism at 15 years follow-up. | Preoperative SEQ and ablation depth were significantly correlated with refractive regression. Regression depended on both sphere and cylinder, and the combination of these two parameters should be considered to predict changes in refraction. The model predicted 2.00-D myopic regression for an ablation depth of 130 µm at 15 years after PRK. |
| Nakamura et al. (2016) [ 27 ] | Postoperative outcomes of 23 eyes with LASIK and 23 eyes with tPRK were evaluated between six months and seven years and compared. | Slight myopia developed in the LASIK (- 0.18 D)- and tPRK (- 0.36 D)-treated eyes and was significantly greater in the tPRK group. A significant difference in corneal power change was found between the LASIK (0.23 D steeper)- and tPRK (0.57 D steeper)-treated eyes. Myopic regression was more pronounced in the tPRK-treated eyes than in the LASIK-treated eyes. |
| Mohammadi et al. (2015) [ 22 ] | Comparing 70 eyes requiring re-treatment versus 158 control eyes not requiring re-treatment, at least nine months after PRK for myopia or myopic astigmatism. | Preoperative SEQ of > -5.00 D, intended OZ < 6.00 mm, and ocular fixation instability during laser ablation were significantly associated with under-correction and regression, and their significance remained in the multiple logistic regression model. |
| Guerin et al. (2012) [ 28 ] | Outcomes of myopic PRK for 120 eyes (80 patients) over 2 ‒ 16-year follow-up. | Postoperative manifest refraction changed in all eyes over the 16 years. Initially, there was a hyperopic shift, with subsequent sharp regression over the first 12 months, followed by stabilization of refraction. At 12 and 16 years post-PRK, 81% and 79.5% of eyes were within 1.00 D of emmetropia, respectively. No correlation was found between keratometric data analyzed for postoperative ectasia and myopic regression, probably implying a latent lenticular etiology in eyes with myopia. |
| Na et al. (2012) [ 29 ] | LASIK-treated eyes (n = 577) and 577 propensity score-matched surface-ablated eyes i.e. LASEK, epi-LASIK, and PRK were included in this three-year follow-up study. | Myopic regression was observed in the surface ablation-treated eyes through postoperative years 1 and 2, yet this difference had no significant effect on visual acuity. |
| Koshimizu et al. (2010) [ 30 ] | Outcomes of myopic PRK for 42 eyes of 29 patients with > 10-year follow-up. | At the 10-year follow-up, 55% and 76% of the eyes were within 1.0 D and 2.0 D, respectively. All eyes had a mild myopic regression with a mean change of - 0.51 ± 1.78 D in refraction. |
| Shojaei et al. (2009) [ 12 ] | Outcomes of myopic PRK for 371 eyes of 203 patients with eight-year follow-up. | They detected myopic regression in 31 eyes (15.97%), which was significant in 11 eyes and required retreatment. Most refractive regressions were detected in the first 18 months and had a significant positive correlation with preoperative spherical refraction. Refractive regressions stabilized within two years. |
| Alio et al. (2008) [ 31 ] | Evaluation of 267 eyes of 191 patients with myopia (SEQ > - 6 D) treated with myopic PRK at three months, one year, two years, five years, and 10 years postoperatively. | At 10 years, 156 (58%) eyes were within 1.00 D and 209 (78%) were within 2.00 D, and retreatment was performed for 124 eyes (46.4%) because of overcorrection, regression, or both. |
| Alio et al. (2008) [ 11 ] | Evaluation of 225 eyes of 138 myopic patients (SEQ: 0 to - 6 D) treated with myopic PRK, 10 years postoperatively. | At 10 years, 169 (75%) of 225 eyes were within 1.00 D and 207 (92%) were within 2.00 D, and retreatment was performed for 95 (42%) eyes because of overcorrection, regression, or both. |
| Kuo et al. (2004) [ 32 ] | The incidence of myopic regression ≥ -1.0 D in 542 consecutive patients, ≥ 3 months after myopic PRK. | In ten eyes of eight patients, they observed late-onset haze with myopic regression > - 1.00 D, for a prevalence of 1.8%. The mean SEQ regression was - 2.01 ± 0.79 D (ranging from - 1.00 to - 3.00 D). Regression stabilized at 6 to 15 months postoperatively. The amount of regression was not correlated with the magnitude of the attempted correction but was correlated with topographic steepening. The study suggested at least 10 months of follow-up for stabilization of refraction post-PRK. |
| Honda et al. (2004) [ 33 ] | Retrospective evaluation of 15 PRK-treated eyes of eight patients after five years. | There was a tendency toward myopic regression within the first postoperative year, and mean manifest refraction changed significantly from + 0.80 ± 1.62 D at 1 week to - 0.45 ± 0.70 D at 1 year. The tendency for regression continued after the second year. They found a significant difference between the mean manifest refraction at two years (- 0.36 ± 0.75 D) and 5 years (- 1.11 ± 1.12 D). Thus, myopic regression was detected in the first year, and a mild regression of approximately - 0.75 D continued between two and five years. |
| Pietila et al. (2004) [ 13 ] | Eight-year outcomes of myopic PRK with a 5.0-mm ablation zone in 92 eyes of 55 patients. | At eight years post-PRK, the percentages of eyes within 1.00 D of emmetropia for low, moderate, and high myopia were 78.3%, 68.8%, and 57.1%, respectively. In all subgroups of myopia, change in myopic regression stabilized within 12 months, yet a small myopic shift was detected up to eight years postoperatively. |
| Wu et al. (2000) [ 23 ] | Two-year outcomes of myopic PRK for 214 eyes of 121 patients with myopia of - 1.00 D to - 6.00 D in 124 eyes and - 6.25 to - 16.00 D in 90 eyes. | Myopic regression had a significant positive correlation with degree of attempted correction (rate of regression: 9.7% versus 27.8% in mild to moderate myopia compared with high myopia). Those in the older age group had a significantly higher regression rate than younger patients. Nearly severe subepithelial haze often coincided with the regression. The main factors causing post-PRK myopia regression were the degree of attempted correction, patient age, and presence of corneal haze. |
| Katlun et al (2000) [ 24 ] | Outcomes of myopic PRK for 338 eyes of 212 patients with myopia ranging from - 1.25 D to -11.25 D up to 12-month follow-up. | Regression and persistent haze were observed in 17 eyes with preoperative refraction > - 6.0 D and mean regression of - 1.67 D at 12 months post-PRK. Haze ≥ grade 1 ‒ 2 at 12 months post-PRK was correlated with regression and a loss of best-corrected visual acuity. |
| Haw et al. (2000) [ 34 ] | Outcomes of photoastigmatic refractive keratectomy in 93 eyes of 56 patients with primary compound myopic astigmatism who had baseline sphere of - 1.0 to - 7.0 D and cylinder of - 1.0 to - 5.0 D were reported up to 12 months postoperatively. | Between 1 and 12 months of postoperative evaluation, a mean myopic regression of 0.27 D was detected. |
Abbreviations: PRK, photorefractive keratectomy; LASIK, laser-assisted in situ keratomileusis; tPRK, transepithelial photorefractive keratectomy; mm, millimeters; OZ, optical zone; n, numbers; SEQ, a spherical equivalent of refractive error in refraction; K, keratometry reading; UCDVA, uncorrected distance visual acuity; Sphere, a spherical component of refractive error in refraction; D, diopter; Cylinder, a cylindrical component of refractive error in refraction; µm, micrometers; LASEK, laser sub-epithelial keratomileusis; epi-LASIK, epithelial laser-assisted in situ keratomileusis.