title: Ablation depth and its effects on corneal biomechanical changes in laser in situ keratomileusis and epipolis laser in situ keratomileusis.
abstract: To assess the corneal biomechanical parameters prior to and following laser in situ keratomileusis (LASIK) and epipolis laser in situ keratomileusis (epi-LASIK) and evaluate the probable correlative factors. Corneal hysteresis (CH), corneal resistance factor (CRF) and other biomechanical metrics were measured and evaluated with an ocular response analyzer preoperatively and 1 month postoperatively. Compared with preoperative values, CH and CRF decreased significantly after surgery in both groups (P = 0.000). The LASIK group exhibited a positive correlation between ablation depth (AD) and ∆CH/∆CRF with a strong r value (r = 0.543, P = 0.000; r = 0.574, P = 0.000). In the epi-LASIK group, however, the correlation was much weaker (r = -0.090, P = 0.682; r = 0.093, P = 0.673), although there were no significant differences between LASIK and epi-LASIK groups in postoperative CH (P = 0.730) and CRF (P = 0.736), and in the changes between CH (P = 0.539) and CRF (P = 0.881). Corneal biomechanical changes correlated with AD in LASIK but not in epi-LASIK, and it appeared that patients with identical demographics and similar attempted corrections are more likely to face a greater danger when undergoing LASIK than epi-LASIK. Therefore, the surface ablation procedure was recommended instead of lamellar ablation especially for correcting high myopia from a biomechanical viewpoint.
authors.affiliation: Tianjin Eye Hospital and Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, No. 4. Gansu Rd, Heping District, Tianjin, 300020, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000503:physiopathology* / Q000601:surgery; D012044:Regression Analysis; D055815:Young Adult