Abstract:Objective The aim of this study was to investigate the corneal resistance factor (CRF) and corneal hysteresis (CH) before laser in situ keratomileusis (LASIK) and to determine their relationship to central corneal thickness (CCT) and to compare the biomechanical properties of the preoperative and postoperative periods of LASIK surgery. Methods This was a case-control study. Eighty-four patients (168 eyes) were selected from January 2010 to February 2010 in Shanxi Eye Hospital who were scheduled to undergo LASIK surgery. CH and CRF values were compared to three corneal thicknesses (group A, 550-643 μm; group B, 500-549 μm; group C, 450-499 μm). An Optical Reaction Analyzer (ORA) was used for measurements. Complete records were obtained from 40 patients (80 eyes) who visited regularly for 1 year and a comparative analysis of the corneal biomechanical characteristics were available for both the preoperative and postoperative periods (1, 3, 6, 1 months). A one-way ANOVA were used for data analysis using SPSS 13.0 software. Results The CRF and CH values for the three preoperative central corneal thickness groups were: 11.11±1.69 and 10.79±1.48, 9.83±1.39 and 9.87±1.29, 9.06±1.96 and 9.79±1.76. The differences were statistically significant (F=19.55, P<0.01; F=8.54, P<0.01). The differences in the CRF and CH values for the preoperative and postoperative periods were also statistically significant (F=102.88, P<0.01; F=60.80, P<0.01). But the CRF and CH values for the different postoperative periods were not statistically significant. Conclusion The CRF and CH values decreases with decreased corneal thickness. Corneal biomechanical characteristics are reduced significantly after LASIK surgery, but there is no change during the postoperative period after LASIK. More than 50% of the entire corneal thickness is composed of the residual corneal stroma that is fairly stable and safe after LASIK.
贺瑞,周迎霞,牛建敏. LASIK手术前后角膜生物力学特性的比较[J]. 中华眼视光学与视觉科学杂志, 2012, 14(2): 106-108.
HE Rui,ZHOU Ying-xia,NIU Jian-min. A study of the corneal biomechanical characteristics in the preoperative and postoperative periods of laser in situ keratomileusis surgery. Chinese Journal of Optometry Ophthalmology and Visual Science, 2012, 14(2): 106-108. DOI: 10.3760/cma.j.issn.1674-845X.2012.02.010
Geggel HS, Talley AR. Delayed onset keratectasia following laser in situ keratomileusis. J Cataract Refrect Surg,1999,25:582-586.
[2]
Amoils SP, Deist MB, Gous P, et al. Iatrogenic keratectasia after laser in situ keratomileusis for less than -4.0 to -7.0 diopters of myopia. J Cataract Refract Surg,2000,26:967-977.
[3]
Dupps WJ Jr. Biomechanical modeling of corneal ectasia. J Refract Surg,2005,21:186-190.
[4]
Guirao A. Theoretical elastic response of the cornea to refractive surgery: risk factors for keratectasia. J Refract Surg 2005,21:176-185.
[5]
Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg,1998,14:312-317.
[6]
Guirao A. Theoretical elastic response of the cornea to refractive surgery: risk factors for keratectasia. J Refract Surg,2005,21:176-185.
Shah S, Laiquzzaman M, Yeung I, et al. The use of the Ocular Response Analyser to determine corneal hysteresis in eyes before and after excimer laser refractive surgery. Cont lens Anterior Eye,2009,32:123-128.
[11]
Caitriona K, Michael O. Corneal hysteresis using the Reichert Ocular Response Analyser: findings pre- and post-LASIK and LASEK,Acta Ophthalmol,2008,86:215-218.
[12]
Sunil Shah, Mohammed Laiquzzaman, Rajan Bhojwani, et al.Assessment of the biomechanical properties of the cornea with the Ocular Response Analyzer in normal and keratoconic eyes. Invest Ophthalmol Vis Sci,2007,48:3026-3031.
[13]
Ortiz D, Pi?ero D, Shabayek MH, et al. Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes. J Cataract Refract Surg,2007,33:1371-1375.