Comparison of corneal hysteresis and corneal resistance factor after small-incision lenticule extraction and photorefractive keratectomy

Abstract

Purpose The aim of this study was to compare the corneal hysteresis (CH) and corneal resistance factor (CRF) after small-incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK). Patients and methods Fifty-six eyes of 28 patients were included in this study. The study eyes had myopia or myopic astigmatism with spherical equivalent less than or equal to −6 D. They were divided into two groups: group I (28 eyes of 14 patients) was corrected using the SMILE technique and group II (28 eyes of 14 patients) was corrected using the PRK technique. CH and CRF were measured in all eyes preoperatively and postoperatively using the ocular response analyzer instrument. Best-corrected visual acuity, spherical equivalent, and central corneal thickness were documented preoperatively and postoperatively in each follow-up visit. All patients were followed up at 3, 6, and 12 months postoperatively. Results The mean patients’ age was 23.8±4.2 years in group I and 24.1±4.7 years in group II (P=0.85). In the SMILE group, CH changed from 10.57±0.38 preoperatively to 8.6±0.26 at 12 months postoperatively (P<0.001), whereas in the PRK group it decreased from 10.7±0.4 to 8.7±0.26 (P<0.001). CRF changed from 10.21±0.1 to 8.4±0.2 and from 10.2±0.11 to 8.5±0.22 after SMILE and PRK, respectively (P<0.001). There were no significant changes in corneal biomechanical factors between SMILE and PRK after 12 months (P=0.1). Conclusion CH and CRF decreased after SMILE and PRK. There were no differences between SMILE and PRK treatments in postoperative CH or CRF values.

Keywords

• corneal biomechanics
• corneal hysteresis
• corneal resistance factor
• photorefractive keratectomy
• small-incision lenticule extraction