经上皮准分子激光角膜表面切削术（TransPRK）对角膜光密度与角膜高阶像差的影响

目的　观察经上皮准分子激光角膜表面切削术（transepithelial photorefractive keratectomy，TransPRK）对角膜光密度与角膜高阶像差的影响，并分析二者的相关性。方法　选取于2017年3月至7月在新乡医学院第一附属医院眼科行TransPRK治疗近视及近视散光的患者80例，均选取右眼纳入研究。对比患眼术前与术后1个月、3个月、6个月角膜光密度与高阶像差的变化情况。术前与术后不同时间点差异的比较采用LSD-t检验，角膜光密度和高阶像差之间的相关性应用Pearson相关分析。结果　在TransPRK术后1个月、3个月、6个月以角膜顶点为中心≤2 mm、＞2~6 mm和＞6~10 mm区域内角膜光密度均较术前明显增高，差异均有统计学意义（均为P＜0.05）。术后1个月、3个月、6个月，总高阶像差、彗差、球差均较术前明显升高，差异均有统计学意义（均为P＜0.05）；三叶草像差在术后1个月、3个月与术前相比差异均有统计学意义（均为P＜0.05）；二级散光差在术后1个月与术前相比差异有统计学意义（P＜0.05）。术后3个月以角膜顶点为中心≤2 mm区域内角膜光密度的变化值与球差的变化值存在负相关性（r=-0.252，P=0.024）。以角膜顶点为中心＞2 ~6 mm区域内角膜光密度变化值与总高阶像差、彗差的变化值均存在正相关性（r=0.403、0.567，均为P=0.000）；与球差的变化值存在负相关性（r=-0.607，P=0.000）。术后6个月时以角膜顶点为中心≤2 mm区域内角膜光密度的变化值与球差的变化值存在负相关性（r=-0.257，P=0.021）；以角膜顶点为中心＞2 ~6 mm区域内角膜光密度变化值与彗差的变化值存在正相关性（r=0.244，P=0.029），与球差的变化值存在负相关性（r=-0.374，P=0.001）。结论　角膜光密度可以作为评判角膜健康情况的定量客观指标，其可以评估TransPRK术后患者角膜的恢复情况，并且预测或者提示术后高阶像差的变化。

Changes and correlation of corneal optical density and corneal higher-order aberrations after transepithelial photorefractive keratectomy

Objective　To observe the changes in corneal optical density and higher order aberrations (HOAs) after transepithelial photorefractive keratectomy (TransPRK) and to analyze the correlation between the corneal optical density and HOAs.Methods　Totally 80 patients (80 right eyes) of myopia and astigmatism were selected from the First Affiliated Hospital of Xinxiang Medical University from March to July 2017.The change of HOAs and the corneal optical density of patients were compared before and after TransPRK at 1 day，1 month,3 months and 6 months.LSD-t test was used to compare the change between pre-operative and different time points of post-operative data.Pearson correlation analysis was applied to analyze the correlation between corneal optical density and HOAs.Results　After TransPRK,the corneal optical density from the area of corneal vertex to 2 mm,>2 mm to 6 mm,>6 mm to 10 mm significantly increased when compared with before operation during the entire follow-up period (all P<0.05).The postoperative values of corneal HOAs root mean square (HO-RSM),coma and spherical aberration were significantly increased at 1 month,3 months and 6 months (all P<0.05).There were significant differences between pre-operative and post-operative trefoil at 1 month and 3 months (all P<0.05).There were statistical differences between pre-operative secondary astigmatism and post-operative data at 1 month (P<0.05).At 3 months after operation,there was a negative correlation between the change of corneal optical density from the area of corneal vertex to 2 mm and the spherical aberration (r=-0.252,P=0.024),while the variation of corneal optical density in the area from 2mm to 6 mm and HO-RMS as well as coma had a positive correlation r=0.403,0.567,both P=0.000).In addition,there was a negative correlation between the change of corneal optical density in the area from 2 mm to 6 mm and the spherical aberration r=-0.607,P=0.000).After TransPRK,there was a negative correlation between the change of corneal optical density that the area from corneal vertex to 2 mm and the spherical aberration at 6 months r=-0.257,P=0.021).Finally,6 months after TransPRK,there was a positive relevant between the change of corneal optical density that the area from 2 mm to 6 mm and the coma r=0.244,P=0.029);on the contrary,there was a negative relationship with spherical aberration r=-0.374,P=0.001).Conclusion　Corneal optical density,as a quantitative and objective index,can evaluate corneal health and the recovery of refractive surgery patients,predict the changes of HOAS after TransPRK.