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.
Cornea Biomechanical properties Laser in situ keratomileusis (LASIK) Epipolis laser in situ keratomileusis (epi-LASIK)
This is a preview of subscription content, log in to check access.
This work was supported in part by the National Key Natural Science Program Grant 81170873 and Tianjin Health Ministry Science Program Grant 2012KY29.
Conflict of interest
The authors have no proprietary or commercial interest in any of the materials discussed in this article.
McDonald M (2007) A return to PRK. Cataract and refractive surgery today, pp 75–77 Google Scholar
MacCrae SM (2005) Surface vs. lamellar: which is best? ISRS/AAO 2005 Refractive surgery—simply the best. Program and abstracts of the American Academy of Ophthalmology 109th Annual Meeting, Chicago, Illinois Oct 15–18 2005Google Scholar
Tobaigy FM, Ghanem RC, Sayegh RR, Hallak JA, Azar DT (2006) A control-matched comparison of laser epithelial keratomileusis and laser in situ keratomileusis for low to moderate myopia. Am J Ophthalmol 142:901–908PubMedCrossRefGoogle Scholar
De Benito-Llopis L, Teus MA, Sanchez-Pina JM, Hernández-Verdejo JL (2007) Comparison between LASEK and LASIK for correction of low myopia. J Refract Surg 23:139–145PubMedGoogle Scholar
Klein SR, Epstein RJ, Randleman JB, Stulting RD (2006) Corneal ectasia after laser in situ keratomileusis in patients without apparent preoperative risk factors. Cornea 25:388–403PubMedCrossRefGoogle Scholar
Guirao A (2005) Theoretical elastic response of the cornea to refractive surgery: risk factors for keratectasia. J Refract Surg 21:176–185PubMedGoogle Scholar
Elsheikh A, Wang D, Pye D (2007) Determination of the modulus of elasticity of the human cornea. J Refract Surg 23:808–818PubMedGoogle Scholar
Luce DA (2005) Determining in vivo biomechanical properties of the cornea with an ocular response analyzer. J Cataract Refract Surg 31:156–162PubMedCrossRefGoogle Scholar
Ortiz D, Pinero D, Shabayek MH, Arnalich-Montiel F, Alió JL (2007) Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes. J Cataract Refract Surg 33(8):1371–1375PubMedCrossRefGoogle Scholar
Kirwan C, O’Keefe M (2008) Corneal hysteresis using the Reichert ocular response analyser: findings pre- and post-LASIK and LASEK. Acta Ophthalmol (Copenh) 86:215–218CrossRefGoogle Scholar
Hamilton DR, Johnson RD, Lee N, Bourla N (2008) Differences in the corneal biomechanical effects of surface ablation compared with laser in situ keratomileusis using a microkeratome or femtosecond laser. J Cataract Refract Surg 34(12):2049–2056PubMedCrossRefGoogle Scholar
Durrie DS, Slade SG, Marshall J (2008) Wavefront-guided excimer laser ablation using photorefractive keratectomy and sub-Bowman’s keratomileusis: a contralateral eye study. J Refract Surg 24:77–84Google Scholar
Kamiya K, Shimizu K, Ohmoto F (2009) Comparison of the changes in corneal biomechanical properties after photorefractive keratectomy and laser in situ keratomileusis. Cornea 28(7):765–769PubMedCrossRefGoogle Scholar
Pallikaris IG, Katsanevaki VJ, Kalyvianaki MI, Naoumidi II (2003) Advances in subepithelial excimer refractive surgery techniques: epi-LASIK. Curr Opin Ophthalmol 14(4):207–212PubMedCrossRefGoogle Scholar
Pallikaris IG, Kalyvianaki MI, Katsanevaki VJ, Ginis HS (2005) Epi-LASIK: preliminary clinical results of an alternative surface ablation procedure. J Cataract Refract Surg 31(5):879–885PubMedCrossRefGoogle Scholar
Roberts C (2000) The cornea is not a piece of plastic. J Refract Surg 16:407–413PubMedGoogle Scholar
Marshal J (2006) Biomechanics and why surface ablation is so important. Paper presented at the 5th international congress on Epi-LASIK and LASEK advanced surface ablation London, UK, Sept 8 2006Google Scholar
Schmack I, Dawson DG, McCarey BE, Waring GO 3rd, Grossniklaus HE, Edelhauser HF (2005) Cohesive tensile strength of human LASIK wounds with histologic, ultrastructural, and clinical correlations. J Refract Surg 21:433–445PubMedGoogle Scholar
Dawson DG, Grossniklaus HE, McCarey BE, Edelhauser HF (2008) Biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery: is there a difference between advanced surface ablation and sub-bowman’s keratomileusis? J Refract Surg 24:S90–S96PubMedGoogle Scholar
Seiler T, Matallana M, Sendler S, Bende T (1992) Does Bowman’s layer determine the biomechanical properties of the cornea? Refract Corneal Surg 8:139–142PubMedGoogle Scholar
Baek TM, Lee KH, Kagaya F, Tomidokoro A, Amano S, Oshika T (2001) Factors affecting the forward shift of posterior corneal surface after laser in situ keratomileusis. Ophthalmology 108:317–320PubMedCrossRefGoogle Scholar