Abstract
Purpose: To assess the changes in the posterior corneal curvature, asphericity and longitudinal spherical aberrations after myopic laser in situ keratomileusis (LASIK)
Method: Prospective nonrandomized comparative study. 68 eyes of 16 women and 18 men were included, with mean age at the time of surgery of 24.79 +3.47 (range 20-35) years ,with a spherical equivalent(SEQ) of -1.5 to -11.75 (mean ,-5.00 +2.168). All procedures were accomplished with the Star S4 IR excimer laser and the Moria microkeratome. (Flap size 90/130 microns). The residual stromal bed thickness of > 250 um or >50% of original thickness of the cornea was maintained. Subjective refractometry, corneal topographical analysis and pachymetry with Sirius (placido disc topography with Scheimpflug tomography) were performed before and 3 months after LASIK for myopia (n=12, range -1.5 D to -5.12 D, mean - 3.20+2.10 D ) and myopic astigmatism (n=56, sphere -1.5 to-10.75 D, mean -4.78 + 2.13 D, cylinder -0.25 D to-3.5D, mean -1.07 + 0.78D).
Results: Paired‘t’ test was used for analysis. A P value < 0.05 was considered to be statistically significant. Overall, change of posterior corneal curvature (-6.259+0.18D/-6.27+0.21 D, P=0.10) was not statistically significant. Change of asphericity (0.89+0.25/1.03+0.12, P <0.001) was highly significant. Change in longitudinal spherical aberrations (0.45+0.33/0.61+0.83, P=0.16) was not found to be significant.
Conclusion: No significant change is seen in the Posterior corneal power/ Longitudinal spherical aberrations following LASIK, but change in asphericity of the cornea (from prolate to oblate) is significant.
References
- Pallikaris IG, Papatzanaki ME, Stathi EZ, Frenschock O, Georgiadis A. Laser in situ keratomileusis. Lasers Surg Med. 1990;10:463–468.
- Dupps WJ Jr. Biomechanical modeling of corneal ectasia.J Refract Surg. 2005;21:186–190.
- Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomilieusis. J Refract Surg 1998; 14:3 12-7.
- Seiler T, Quurke A W. Iatrogenic keratectasia after LASIK in a case of forme frustekeratoconus. J Cataract Refract Surg 1998; 24:1007-9.
- Probst LE, Machat JJ. Mathematics of laser in situ keratomilieusis for high myopia. J Cataract Refract Surg 1998;24:190-5.
- Wang Z, Chen J, Yang B. Posterior corneal surface topographic changes after laser in situ keratomilieusis are related to residual corneal bed thickness. Ophthalmology. 1999;106:406-409.
- Seitz B, Torres F, Langenbucher A, Behrens A, Suarez E. Posterior Corneal Curvature Changes after Myopic Laser In Situ Keratomilieusis. J Ophthalmol 2001 ;108:666-673.
- Azar DT, Koch DD. Laser fundamentals, surgical techniques and complications. Taylor, chapter 2002, 11:163-170.
- Khairat Y, Mohamed Y et al. Evaluation of corneal changes after Myopic LASIK using the Pentacam. Clinical 2013:7; 1771-1776.
- Bottos KM, Leite MT, Aventura-Isidro M, et al. Corneal asphericity and spherical aberration after refractive surgery. J Cataract Refract Surg. 2011;37:1109–1115 .
- Hou J, Wang Y, Li J, Yang XY, Zhang L. Change of asphericity of posterior corneal surface after refractive surgery. Zhonghua Yan Ke Za Zhi. 2011;47:223–227.
- Applegate RA. Limits to vision: can we do better than nature? J Refract Surg. 2000; 16(5): S547-51.
- Applegate RA, Howland HC. Refractive surgery, optical aberrations, and visual performance. J Refract Surg. 1997;13:295-299
- Guillon M, Lydon DP, Wilson C. Corneal topography: A clinical model. Ophthal Physiol Opt. 1986; 6(1):47-56.
- Lam A, Douthwaite W. Measurement of posterior corneal asphericityon Hong Kong Chinese: A pilot study. Ophthal Physiol Opt. 1997;17(4): 348-56.
- Kohnen T, Mahmoud K, Buhren J. Comparison of corneal higher-order aberrations induced by myopic and hyperopic LASIK. Ophthalmology .2005 Oct;112(10):1692.
- Miller JM, Anwaruddin R, et al. Higher order aberrations in normal, dilated, intraocular lens, and laser in situ keratomilieusis corneas. J Refract Surg.2002;18(5):S579-83.
Corresponding Author
Dr Ashok H. Madan
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DOI: https://dx.doi.org/10.18535/jmscr/v6i11.112
