Two-year stability of posterior corneal surface after transepithelial photorefractive keratectomy with a residual stromal thickness less than 350 μm

PURPOSE

This study aimed to investigate the stability of posterior corneal surface 2 years after transepithelial photorefractive keratectomy (TPRK) in patients with a residual stromal thickness less than 350 μm.

METHODS

In total, 408 eyes of 212 patients (160 women, 52 men) who underwent TPRK were enrolled in this retrospective study. All surgeries were performed in the Amaris 750S excimer laser platform with smart pulse technology. The posterior corneal elevation, anterior chamber depth, Q value, and curvature were measured using Pentacam preoperatively and postoperatively. All patients were followed up for 2 years. The relationship between percent tissue altered (PTA), age, and changes in posterior corneal surface was analyzed.

RESULTS

The mean preoperative spherical equivalent was - 6.80 ± 1.18 D (range: - 9.00 to - 2.63 D). The mean residual stromal thickness was 336.46 ± 7.25 μm (range: 310-348 μm). The mean PTA was 30.93 ± 2.03% (range: 24.29-35.28%). At 2 years after surgery, the elevation of six points in the central area decreased by 1.91 ± 2.97 μm, 2.98 ± 3.23 μm, 1.17 ± 3.85 μm, 1.70 ± 2.88 μm, 1.36 ± 3.19 μm, and 1.65 ± 3.18 μm, compared with the preoperative value (P < 0.05). The elevation of three points in the peripheral area increased by 1.87 ± 6.34 μm, 0.68 ± 6.00 μm, and 0.95 ± 5.50 μm (P < 0.05). There was no significant linear relationship between PTA, age, and changes in posterior corneal surface, anterior chamber depth, and K2 (all P > 0.05).

CONCLUSION

Within 2 years after TPRK, the posterior corneal surface remained stable in patients with a residual stromal thickness between 310 and 350 μm. There was no sign of iatrogenic ectasia during the follow-up period.

Role of corneal epithelial thickness during myopic regression in femtosecond laser-assisted in situ keratomileusis and transepithelial photorefractive keratectomy

BACKGROUND

The study aimed to investigate the relationship between changes in corneal epithelial thickness and the outcome of myopic regression after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and transepithelial photorefractive keratectomy (TPRK).

METHODS

This study included 45 eyes of 25 patients undergoing FS-LASIK and 44 eyes of 24 patients undergoing TPRK. Myopic regression occurred in these patients postoperatively from 8 to 21 months. The corneal epithelial thickness was measured using a spectral-domain optical coherence tomography at the onset of regression, 3 months after treatment, and 3 months after drug withdrawal.

RESULTS

Compared with that of preoperation, corneal epithelial thickness increased when regression occurred in both groups (all P < 0.05). The thickness of central corneal epithelium in FS-LASIK and TPRK groups reached 65.02 ± 4.12 µm and 61.63 ± 2.91 µm, respectively. The corneal epithelial thickness decreased when myopic regression subsided after 3 months of steroid treatment compared to the onset (P < 0.05). With a decrease in corneal epithelial thickness, the curvature of the anterior corneal surface, central corneal thickness, and refractive power all decreased (all P < 0.05). The corneal epithelial thickness and refractive error remained relatively stable after 3 months of treatment withdrawal (P > 0.05).

CONCLUSION

The corneal epithelial thickness determined the outcome of myopic regression similarly in FS-LASIK and TPRK. When the corneal epithelium thickened, regression occurred. After steroid treatment, epithelial thickness decreased whereas regression subsided.

Comparison of clinical results between trans-PRK and femtosecond LASIK for correction of high myopia

Background

To compare the clinical outcomes of transepithelial photorefractive keratectomy (TPRK) with femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correction of high myopia.

Methods

In this prospective, non-randomised, cohort study, 85 eyes of 46 patients treated with TPRK and 80 eyes of 42 patients treated with FS-LASIK were included. All eyes were highly myopic (spherical equivalent refraction <− 6.00 diopters). Both TPRK and FS-LASIK were performed by Schwind Amaris 750S excimer laser. Visual acuity, refraction, corneal high order aberration (HOA) and other variables were analyzed before and at 1, 3, 6, 12 months after surgery.

Results

At 12 months after surgery, uncorrected logMAR distance visual acuity (UDVA) in the TPRK and FS-LASIK groups was − 0.04 ± 0.04 and − 0.01 ± 0.08, respectively (P = 0.039). Corrected logMAR distance visual acuity (CDVA) was − 0.06 ± 0.05 and − 0.04 ± 0.05 in both groups (P = 0.621). For UDVA, 86% of eyes in the TPRK group and 80% in the FS-LASIK group remained unchanged or improved one or more logMAR lines (P = 0.314), compared to preoperative CDVA. For CDVA, 97% of eyes in the TPRK group and 90% in the FS-LASIK group remained unchanged or improved one or more lines (P = 0.096), compared to preoperative CDVA. Spherical equivalent refraction was − 0.05 ± 0.39 and − 0.26 ± 0.47 in both groups (P = 0.030). 87% of eyes in the TPRK group and 73% in the FS-LASIK group achieved ±0.50 D target refraction (P = 0.019). All 85 eyes (100%) in the TPRK group and 75 eyes (92%) in the FS-LASIK group were within ±1.00 D of target (P = 0.003). Root mean square (RMS) of corneal total HOA and vertical coma in the TPRK group were lower compared with the FS-LASIK group (P < 0.001 for both variables).

Conclusions

TPRK and FS-LASIK showed good safety, efficacy and predictability for correction of high myopia. Clinical outcomes of TPRK were slightly better than FS-LASIK.