International Journal of Keratoconus and Ectatic Corneal Diseases

Register      Login

VOLUME 3 , ISSUE 1 ( January-April, 2014 ) > List of Articles

RESEARCH ARTICLE

Corneal Biomechanical Properties Post-LASEK for the Correction of Myopia

David Zadok, Ali Nassar

Citation Information : Zadok D, Nassar A. Corneal Biomechanical Properties Post-LASEK for the Correction of Myopia. Int J Kerat Ect Cor Dis 2014; 3 (1):23-28.

DOI: 10.5005/jp-journals-10025-1073

Published Online: 01-04-2014

Copyright Statement:  Copyright © 2014; Jaypee Brothers Medical Publishers (P) Ltd.


Abstract

Introduction

Laser surgeries are effective and safe, however, over the years data has accumulated about several complications of the procedures, particularly corneal ectasia. Various studies demonstrated the importance of the front layers of the cornea to keep its structure fixed. In order to correct various degrees of myopia, different thicknesses of tissue have to be removed. Therefore, it is conceivable that the risk of developing ectasia might increase depending on the depth of corneal tissue removed.

In the last few years, the Reichert Ocular Respond Analyzer (ORA) for measuring the biomechanical parameters of the cornea has been introduced. Studies demonstrated a decrease in the corneal biomechanical parameters after Laser Assisted Sub-epithelial Keratomileusis (LASEK) surgery. However, the, relation between the depth of tissue removed and the amount of change in the biomechanical parameters had not been tested yet.

Purpose

To evaluate the relationship between corneal biomechanical parameters and corneal tissue ablation thickness.

Methods

Data was retrospectively collected from patient's files that underwent LASEK in private medical center – Hadassah Optimal in Haifa between January 2009 and May 2010. All patients were operated by same surgeon (AB). In our study we included patients that had at least three ORA measurements at three set periods of time; before the operation, up to 3 months postoperative and more than 3 months postoperative. We divided the patients into 3 groups depending on the refractive error and tested the effect of variable factors (Age, Total depth ablated-TDA, percent of total depth ablated-%TDA, sex, refraction). The data was analyzed by descriptive statistics and student t-test to find the relation between LASEK and the corneal biomechanical parameters.

Results

Ninety-eight patients participated in our study, which included 98 separate eye operations. A statistically significant decrease (p < 0.001) was found in CRF, CH, IOPg after LASEK. In group 1 (refraction −0.5 to −2.99): on CH – there was a statistically significant (p < 0.05) weak-moderate effect of TDA and %TDA (Pearson coefficient of 0.4, 0.39 respectively), statistically significant (p < 0.05) effect of age. On CRF — we found a statistically significant (p < 0.05) weak-moderate effect of TDA and %TDA (Pearson coefficient of 0.36 for both factors), statistically significant (p < 0.05) effect of age. In the second group (refraction value −3 to −5.99) only on IOPg a statistically significant (p < 0.05) weak effect of TDA (Pearson coefficient of 0.33) was demonstrated. In the third group, we did not find any effect of the variable factors on the change in biomechanical properties characteristics after LASEK.

Importance

Corneal biomechanical properties influence corneal behavior in certain eye diseases. Moreover, it has been noted that operations and procedures affect these biomechanical properties of the cornea. Hence, it is of great importance to reveal factors that could affect and change such parameters.

How to cite this article

Barbara R, Nassar A, Zadok D, Barbara Corneal Biomechanical Properties Post-LASEK for the Correction of Myopia. Int J Kerat Ect Cor Dis 2014;3(1):23-28.


PDF Share
  1. Refractive surgery: the future of perfect vision. Singapore MED J 2007;48(8):709-718.
  2. Overview of laser refractive surgery. Chang Gung Med J 31(3):237-254.
  3. Postoperative changes in intraocular pressure and corneal biomechanical metrics, Laser in sito keratomileusis versus laser assisted subepithelial keratectomy. J Cataract Refrac Surg 2009 Oct;35:1774-1788.
  4. The use of ocular response analyzer to determine corneal hysteresis in eyes before and after excimer laser refractive surgery, Contact lens and anterior eye 2009;32:123-128.
  5. Comparison of biomechanical parameters in penetrating keratoplasty and normal eyes using the ocular response analyzer. Clinical and Experimental Ophthalmology 2010;38:758-763.
  6. Determining in vivo biomechanical properties of the cornea with an ocular response analyzer. J Cataract Refract Surg 2005;31:156-162.
  7. Corneal hysteresis, resistance factor, topography, and pachymetry after corneal lamellar flap. J Refract Surg 2007 Jan 23.
  8. What biomechanical properties of the cornea are Relevant for the Clinician? Surv Ophthalmol 2007.
  9. The use of the Reichert ocular response analyzer to establish the relationship between ocular hysteresis, corneal resistance factor and central corneal thickness in normal eyes. Contact Lens and Anterior Eye 2006;29:257-262.
  10. Arnalich-Montiel F, Alio JL. Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes. J Cataract Refract Surg 2007 Aug;33:1371-1375.
  11. Repeatability of intraocular pressure and corneal biomechanical properties measurements by the ocular response analyzer. Klin Monatsbl Augenheilkd 2008;225:357-360.
  12. Evaluation of the influence of corneal biomechanical properties on intraocular pressure measurements using the ocular response analyzer. J Glaucoma 2006;15:364-370.
  13. Factors affecting corneal hysteresis in normal eyes: graefe's archive for clinical and experimental ophthalmology 2007;246(10):1491-1494.
  14. Corneal hysteresis and intraocular pressure measurement in children using the richert ocular response analyzer. Am J Ophthalmol 2006;142:990-992.
  15. Corneal hysteresis using the Reichert ocular response analyzer: findings pre- and post-LASIK and LASEK. Acta Ophthalmol 2008;86:215-218.
  16. Effects of aging on corneal biomechanical properties and their impact on 24-hour measure- ment of intraocular pressure. American J Ophthalmol 2008 Oct;146(4):567-572.
  17. Diurnal variation of ocular hysteresis in normal subjects: relevance in clinical context. Clinical and Experimental Ophthalmology 2006;34:114-118.
  18. Effect of 24-hour corneal biomechanical changes on intraocular pressure measurement. IOVS 2006 Oct;47(10):4422-4426.
  19. Effect of topical corneal anaesthesia on ocular response analyzer parameters: pilot study. Int Ophthalmol, 2008;29(5):325-328.
  20. Changes in corneal hysteresis after clear corneal cataract surgery. American J Ophthalmol 2007 Sep;144(3):341-346.
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.