Long-Term Clinical Evaluation Of Laser In Situ Keratomileusis For High Myopia

Objectives To evaluate long-term visual and refractive outcomes of LASIK.The main outcome measures were efficacy,predictability and safety. Meanwhile,The relationships were investigated between various factors and refractive regression of high myopic subjects who underwent laser in situ keratomileusis(LASIK) for five years ago.Methods The study was a retrospective analysis of 167 eyes of 96 patients who had undergone LASIK with preoperative refraction ranging from -6D to-10D(mean-7.39±1.15D) in the First Affiliated Hospital of Guangxi Medical University from January 2002 to December 2003.The flaps were cut using the Hanstatome microkeratome.Laser ablation was done with Schwind Multiscan. The postoperative follow-up lasted for 5～6 years.All patients had a detailed preoperative and postoperative examination including uncorrected visual acuity(UCVA),best corrected visual acuity(BCVA),spherical equivalent refra- ction,slit lamp examination and dilated fundus examination of one day,seven days,one month,three months,six months,one year,one and a half years,two years,5 years after surgery.In addition,age,intraocular pressure,corneal curvature, corneal pachymetry and postoperative complications were also recorded at last follow-ups.Statistical analysis was performed using SPSS13.0 software.Results(1) The postoperative UCVA of all patients had obvious elevation compared with the UCVA preoperation.The mean uncorrected visual acuity (UCVA) was 0.84±0.35,49.1%of eyes had uncorrected visual acuity of 1.0 or better and 83.2%of 0.5 or better,visual efficacy index was 0.71 after five years postoperatively.(2)All of the postoperative refraction had obvious descent. The mean refraction was -0.55±0.80D,the residual refractive error within±1.0D was 75.4%and within±0.5D was 59.3%after five years postoperatively.(3)The mean BCVA was 1.21±0.19,35.33%of eyes gained 1 line postoperative BCVA after 5 years compared with preoperative BCVA,26.35%of eyes lost 1 line, 0.6%of eyes lost 2 lines,73.05%of eyes were unchanged or improved after five years postoperatively.(4) There were two irregular flaps intraoperatively.Postoperative complications were rare,only two eyes with glare and halo,two eyes with yellow chromatosis in central cornea.3.6%(6/167) patients complained postoperative dry eye syndrome.Above complications occurred within one year after surgery.No other complications had appeared during two to five years,no grave complications,such as diffuse lamellar keratitis,epithelial ingrowth,insecondary keratoconus,etc.(5) Refractive regression was positively correlated with preoperative spherical equivalent refraction.Refractive regression was negatively correlated with the amount of change in corneal curvature.No significant correlation was found between regression and preoperative and postoperative corneal curvature.There was no correlation between regression and intraocular pressure.A negative correlation was found between regression and the amount of changes in central pachymetry.Refractive regression had not correlation with preoperative and postoperative central pachymetry.Refractive regression was negatively correlated with laser ablation diameter.Conclusions(1)The long-term evaluation of LASIK for the correction of high myopia is effective,safe and predictable.The Refractive regression occurs in some cases.(2)Refractive regression was correlated with preoperative spherical equivalent refraction,the amount of preoperative and postoperative change in corneal curvature,the amount of preoperative and postoperative changes in central pachymetry and laser ablation diameter.(3) Preoperative central corneal thickness had been morethan 450 micrometer and residual stromal bed thickness had been over 250 micrometer,there was a important factor for not insecondary keratoconus during five years after surgery.(4)Big laser ablation diameter would help to decrease the rate of glare and the loss of best corrected visual acuity after surgery.