角膜塑形术治疗近视眼安全性的探讨

目的 观察和分析角膜塑形术后角膜形态的变化以及角膜生物力学属性的变化.方法 对30例青少年近视眼患者年龄(11.67±1.63)岁,屈光状态(-2.56±0.86)D]采用夜戴型角膜坦形镜进行近视矫正.分别在戴镜前、戴镜后1 d、1周、1个月、3个月及6个月时用眼反应分析仪(ORA)测量角膜黏滞性(CH)、角膜阻力因子(CRF)、Goldmann相关眼压(IOPg)、角膜补偿眼压(IOPcc),分别用改进的光学相干断层扫描仪(OCT)、计算机辅助的角膜地形图和非接触角膜内皮显微镜测量中央角膜厚度、角膜地形和角膜内皮细胞密度,只取右眼数据用重复性方差分析进行统计学分析.结果 配戴角膜塑形镜1 d后近视度数已开始有效减低.戴镜前、戴镜后1周及6个月平均角膜曲率分别为(43.32±0.21)、(41.66±0.27)和(41.65±1.45)D,差异有统计学意义(F=38.837,P<0.01),1周之后变化趋于稳定.角膜生物力学CH值和CRF值戴镜1 d后也开始降低,1周以后开始恢复,3和6个月时已恢复到戴前水平.戴镜后1周IOPg和IOPcc分别为(9.09±0.38)和(8.52±0.39)mm Hg(1 mm Hg=0.133 kPa),比戴镜前降低,1周时达到最低,1周以后变化趋于稳定.戴镜前后中央角膜厚度在1周时降低,6个月时仍比配戴前低(F=4.739,P<0.05).角膜内皮细胞密度无明显变化.结论 角膜塑形术能有效的降低近视度数集中于1周内,该时间段角膜生物力学属性产生相应的降低变化,但在1周之后的角膜塑形稳定期内,角膜生物力学属性会恢复并保持原来水平,说明角膜塑形未破坏角膜微型结构,其早期的反应可能与角膜对角膜塑形镜片适应过程中的角膜结构暂时性调整有关.

A study on the effect of the corneal biomechanical properties undergoing overnight orthokeratology

Objective To evaluate the changes of corneal biomechanical properties and corneal topography undergoing overnight orthokeratology treatment. Methods Thirty teenagers with low andmoderate myopia with age of 11.67±1.63,myopia(-2.56±0.86)D,were included and were fitted with Ortho-K CL. The corneal biomechanical properties,including corneal hysteresis (CH),corneal resistance factor(CRF),goldmann-correlated lOP(IOPg) and corneal-compensated intraocular pressure(IOPcc) were measured with ocular response analyzer(ORA).Corneal topography,central corneal thickness(CCT) and corneal endothelium density were measured with computerized corneal topography,optical coherence tomography(OCT) and non contact specular microscope respectively.The measurements were taken at pre-wear,1 day and 7,30,90,180 days after orthokeratology.Only data from the right eyes were analysed.Results All subjects were significantly reduced the myopia amount after 1 day of lens Wear.The corneal curvature flattening(F=38.837,P<0.01)became slightly down to stable after the first week.There were significant decrease in CH and CRF after the orthokeratology treatment within the first week,and CH and CRF reversed and thereafeter into the original level at 3-month and 6-month follow up.IOPg and IOPcc decreased and reached the lowwest level at 1-week visit and after then became down to stable.There were significant reduction in CCT after 1 week(F=4.739,P<0.05).There were no significant changes in corneal endothelium density during orthokeratology treatment for 6 months.Conclusions The amount of myopia reduction with orthokeratology occurred mostly within 1 week while the corneal biomechanical properties such as CH and CRF were decreased. However the corneal biomechanical properties are reversal to the original level thereafter and remain unchanged within the 6 months follow up visits.It proves that orthokeratology does not demage corneal microsturcture.The early sign of reduction may due to the temporal response to the reshaping of the cornea.