Comparison of Changes in Corneal Biomechanical Properties after Photorefractive Keratectomy and Small Incision Lenticule Extraction

Abstract

Objectives:To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) in eyes with low and moderate myopia.Materials and Methods:We retrospectively examined 42 eyes of 23 patients undergoing PRK and 42 eyes of 22 patients undergoing SMILE for the correction of low and moderate myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with an Ocular Response Analyzer before and 6 months after surgery. We also investigated the relationship between these biomechanical changes and the amount of myopic correction.Results:In the PRK group, CH was 10.4±1.3 mmHg preoperatively and significantly decreased to 8.5±1.3 mmHg postoperatively. In the SMILE group, CH was 10.9±1.7 mmHg preoperatively and decreased to 8.4±1.5 mmHg postoperatively. CRF was significantly decreased from 10.8±1.1 mmHg to 7.4±1.5 mmHg in the PRK group whereas it was decreased from 11.1±1.5 mmHg to 7.9±1.6 mmHg in the SMILE group postoperatively. There was a significant correlation between the amount of myopic correction and changes in biomechanical properties after PRK (r=-0.29, p=0.045 for CH; r=-0.07, p=0.05 for CRF) and SMILE (r=-0.25, p=0.048 for CH; r=-0.37, p=0.011 for CRF).Conclusion:Both PRK and SMILE can affect the biomechanical strength of the cornea. SMILE resulted in larger biomechanical changes than PRK.

Corneal biomechanical properties after SMILE versus FLEX, LASIK, LASEK, or PRK: a systematic review and meta-analysis

“…The cap diameter was between 7.2 to 8 mm in 16 studies, [25, 30, 36, 38, 41, 45–51, 53, 58–60] and the diameter of the optical zone was between 6 to 7 mm in 19 studies [25, 30, 36, 38–41, 45, 47–49, 51–56, 58, 59]. Twelve studies were performed with an energy between 115 to 190 nJ [30, 36, 38, 40, 41, 45, 47, 49–51, 53, 54, 58].…”

“…The CH/CRF value was greater after PRK/LASEK compared with SMILE although the difference did not reach a significance. In the study of Yildirim et al, the amount of stromal tissue removed by SMILE was significantly greater than PRK [54]. This may bias the result because of the greater lenticule thickness or ablation depth the more decrease of CH and CRF value after refractive surgeries [51, 54].…”

“…In the study of Yildirim et al, the amount of stromal tissue removed by SMILE was significantly greater than PRK [54]. This may bias the result because of the greater lenticule thickness or ablation depth the more decrease of CH and CRF value after refractive surgeries [51, 54]. By contrast, Dou et al did not find a significant difference between SMILE and LASEK in CH or CRF decrease [51].…”

Comparison of Changes in Corneal Biomechanical Properties before and After Photorefractive Keratectomy and Small Incision Lenticule Extraction

“…Surgical correction of refractive errors is becoming progressively popular, quick and effective for correction of myopia, hyperopia and astigmatism [2,3]. Photo refractive keratectomy (PRK) has been administered effectively and reliably for many years in the treatment of myopia [4]. In PRK, the laser is applied directly to the anterior corneal stroma without creating a flap.…”

“…In PRK, the laser is applied directly to the anterior corneal stroma without creating a flap. It is one of the developing procedures that have been engaging to avoid flap creation [4,5].…”