Purchase this article with an account.
M.K. Chang, R.W. Snyder, J. Lee, J.T. Schwiegerling, C. Nedrud; Posterior Corneal Curvature Changes Comparing LASIK Versus LASEK . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2692.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess whether there is a difference in the antero-posterior shift of the posterior corneal surface after LASIK and LASEK surgeries using a scanning-slit topographer. Methods: A chart review of patients who had either LASIK or LASEK for correction of simple myopia or myopic astigmatism from July 2001 to April 2002 was completed. The antero-posterior movement of the posterior float was calculated by using the difference map function on the Orbscan topographer. Three points within the central 4 mm optical zone were measured between the preop and 6 month postop Orbscans: the center, area of greatest posterior float preop, and the point of greatest overall difference. Results: The LASEK group included 28 eyes of 15 patients with a mean preop refraction of –3.93 D sph and +0.61 D cyl. After LASEK, the mean postop refraction was –0.035 D sph and +0.125 D cyl. 89% of eyes achieved a visual acuity of 20/20 or better. All patients were 20/25 or better. The LASIK group included 35 eyes of 19 patients with a mean preop refraction of –4.23 D sph and +0.78 D cyl. After LASIK surgery, the mean postop refraction was –0.55 D sph and +0.67 D cyl. 40% of eyes achieved 20/20 or better vision, and 89% was 20/40 or better. The mean anterior shift between the preop and postop posterior floats at the center, greatest point preop, and overall greatest value was 6.7, 6.9, and 16.9 microns in the LASEK group respectively, and 10.6, 10.1, and 19.1 microns in the LASIK group respectively. There were no statistically significant differences between the groups when all patients were included. The patients were then stratified in a lower (<-4 D) and higher myope group ( > -4 D). There was a statistically significant difference at all three points in the higher myope group between LASEK and LASIK (center p=0.0016; greatest preop point p=0.011; point of greatest overall difference p=0.02). Conclusions: When performing LASIK, a flap is created using a microkeratome. The flap however does not contribute to the structural integrity of the cornea. A few advantages of LASEK surgery are that microkeratome related complications are avoided and there is a greater residual stromal thickness. Theoretically a greater stromal thickness should impart more structural integrity to the cornea. When comparing the anterior shift of the posterior corneal surface after refractive surgery, there was a statistically significant difference between the LASIK and LASEK patients for the higher myopes. In conclusion, LASEK surgery had superior visual acuity results and greater stabilty of the posterior corneal surface.
This PDF is available to Subscribers Only