角膜塑形镜配戴后瞳孔与光学区的大小对视觉质量的影响

Effects of pupil size and treatment zone diameter on optical quality after myopic orthokeratology treatment

目的探究角膜塑形镜治疗后暗室对比敏感度与调制传递函数截止频率(modulation transfer function cutoff,MTF cutoff)变化,并分析瞳孔与光学区的大小对暗室下对比敏感度以及MTF cutoff的影响。方法选取2015年8月至12月在天津医科大学眼科医院进行角膜塑形镜治疗的近视青少年40人(右眼40眼),戴镜前、戴镜后6个月分别测量角膜地形图、暗室瞳孔大小、光学区大小、暗室及暗室眩光条件下对比敏感度曲线下面积(area under log contrast sensitivity function,AULCSF)及MTF cutoff,戴镜前后视觉质量参数变化采用配对t检验,暗室瞳孔与光学区对视觉质量参数的影响采用Pearson相关分析。结果戴镜后6个月等效球镜度数降低(P<0.001),柱镜度数无变化(P=0.879);暗室对比敏感度及暗室眩光条件下对比敏感度均下降(均为P<0.001);MTF cutoff下降(P<0.001)。戴镜前后瞳孔直径为(6.50±0.34)mm。戴镜后6个月光学区直径为(4.05±0.24)mm。暗室条件下AULCSF变化与暗室瞳孔直径及光学区直径均不相关(r=0.159,P=0.307;r=-0.223,P=0.167),暗室眩光条件下AULCSF变化与暗室瞳孔直径及光学区直径均不相关(r=0.174,P=0.289;r=-0.200,P=0.216)。MTF cutoff变化与暗室瞳孔直径及光学区直径相关(r=0.509,P=0.001;r=-0.511,P=0.001),暗室、暗室眩光条件下AULCSF及MTF cutoff变化均与瞳孔直径和光学区直径之差相关(均为P<0.05)。结论角膜塑形镜配戴后暗室对比敏感度及MTF cutoff均降低,且较小的暗室瞳孔与较大的光学区可获得更好的视觉质量。

Objective To analyze the changes in contrast sensitivity and modulation transfer function cutoff values （ MTF cutoff） after orthokeratology （ortho-k） treatment and its correlation with the magnitude of pupil and the diameter of the treatment zone. Methods A prospective study was conducted in 40 eyes of 40 patients wearing orthokeratology contact lens. Mesopic area under log contrast sensitivity function （AULCSF） with and without glare and MTF cutoff were measured and compared before and 6 months after ortho-k lens treatment. The magnitude of pupil and diameter of the treatment zone （TxZ） were tested against the change in AULCSF and MTF cutoff after ortho-k treatment in Pearson correlation test. Results After 6 months of ortho-k treatments, the mean spherical refractive error significantly decreased （ P 〈 0.001 ）, but refractive astigmatism did not significantly change （P = 0. 879 ）. The mesopic AULCSF with and without glare and MTF cutoff significantly decreased after ortho-k lens wear （allP〈0.001）. The mean pupil size was （6.50 ±0.34） mm;The mean TxZ diameter was （4.05 ± 0.24） ram. The mesopic AULCSF with and without glare was significantly correlated with the difference between the magnitude of pupil and the diameter of the TxZ （Dpupil-TxZ） （P = 0. 019 ,r = 0.368 ;P = 0.034 ,r = 0.336, respectively）, but not with the magnitude of pupil （ r = 0. 159 ,P = 0. 307 ; r = - 0. 223 ,P = 0. 167, respectively） and the diameter of the TxZ （P = 0. 289, r = 0. 174 ; P = 0. 216, r = - 0.200, respectively）. The MTF cutoff was significantly correlated with the magnitude of pupil and diameter of the TxZ and Dpupil-TxZ （P = 0. 001, r = 0. 509 ; P = 0. 001, r = - 0.511, respectively）. Con- clusion The contrast sensitivity and MTF cutoff decreases after ortho-k treatment, which can be alleviated by a smaller pupil size and a larger TxZ diameter.