Clinical Outcomes of Smart Pulse Technology Assisted TransPRK to Treat Moderate to High Astigmatism

Objective: To evaluate the clinical efficacy of corneal wavefront aberration-guided TransPRK surgery in the correction of moderate to high astigmatism with the help of smart pulse technology (SPT). Methods: In this retrospective study, TransPRK- corrected myopia in 29 patients (54 eyes) with high astigmatism in Yuncheng City Eye Hospital during July 2016 to December 2017 were examined. The eyes were examined before treatment and 1 month, 3 months and 6 months after treatment for uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and manifest refraction, slit lamp microscopy, intraocular pressure measurements, and Pentacam corneal topography measurements. The preoperative spherical scope ranged from -6.00 to -1.25 D (mean -3.57±1.19 D), and the cylinder range was 1.50 to 4.00 D (mean 2.06± 0.55 D). The clinical outcomes and evaluation of the postoperative astigmatism vector in the correction of myopia with moderate and high astigmatism were evaluated. Preop and postop indexes were analyzed by repeated measurement analysis of variance, and Pearson correlation coefficients were used to assess the correlation between different variables. Results: Six months after surgery, 98% of the eyes had a UCVA of 1.0 or better, and an 87% equivalent spherical value of between ±0.50. The intended refractive correction (IRC) was 2.03±0.51 D, the mean of the surgically induced refractive correction (SIRC) was 2.02±0.69 D, the mean of the error vector (EV) was 0.49±0.35 D, the mean of the error angle (EA) was -1.37±7.62°, the mean of error magnitude (EM) was 0.23±0.40 D, the mean of error ratio (ER) was 0.25±0.19, and the mean of correction ratio (CR) was 0.99±0.21. There were significant correlations between IRC and SIRC (r=0.95, P<0.001), between EM and IRC (r=0.55, P<0.001) and between EV and ER (r=0.92, P<0.001). The EA results suggested that astigmatism changes counterclockwise, with the percentage of eyes in the range of 5° and 15° being 65% (35 eyes) and 96% (52 eyes). The CR results suggested a slight under correction of postoperative astigmatism. Conclusions: Corneal wavefront-guided TransPRK and the smart pulse technology assisted TransPRK show safe, predictable results in the correction of myopia with moderate and high astigmatism. It is necessary to improve the accuracy of astigmatism power and its axial direction before and during the surgery. Key words: astigmatism; vector analysis; transepithelial photorefractive keratectomy; smart pulse technology