角膜塑型镜治疗后镜片偏离中心的角膜地形图分析

目的　探讨角膜塑型镜治疗后镜片偏离中心的相关因素及其对视功能的影响。方法应用HumpheryInstrumentsATLAS 8 0角膜地形图分析系统对 135例 (2 70只眼 )患者配戴角膜塑型镜前及治疗 6个月内的角膜地形图进行定量分析 ,以角膜顶点为参考点 ,检测治疗后光学区中心与角膜顶点的距离 ,即为偏中心距离 ,分析偏中心距离与患者治疗前有关参数之间的关系。分析偏中心距离大小对视功能的影响。结果　治疗 1d、1个月、3个月及 6个月患者平均镜片偏中心距离分别为 (0 4 9±0 34)mm、(0 5 7± 0 4 1)mm、(0 5 5± 0 4 8)mm及 (0 5 9± 0 39)mm。治疗 1个月平均偏中心距离≤0 5mm者 138只眼 (5 1 1% ) ,0 5～ 1 0mm者 96只眼 (35 6 % ) ,>1 0mm者 36只眼 (13 3% )。其中偏中心距离 >0 5mm者中 ,4 8 5 %的患者偏离方向为颞侧。治疗前不同散光度数和不同镜片直径者间的治疗后镜片偏中心距离比较 ,差异均有显著意义 (单因素方差分析 ,P =0 0 5、0 0 0 )。治疗前不同屈光度者间的治疗后镜片偏中心距离比较 ,差异无显著意义 (方差分析 ,P =0 6 4 )。治疗前不同平均角膜曲率半径和不同角膜偏心率E值者间的治疗后镜片偏中心距离比较 ,差异均无显著意义 (t检验 ,P=0 6 4、0 5 1)。治疗后有无发生重影和眩

Topographical evaluation on decentration of orthokeratology lenses

OBJECTIVE: To evaluate the degree and correlative factors of decentration of orthokeratology lenses and its effect on the visual function. METHODS: Two different kinds of orthokeratology lenses were fitted to 270 eyes of 135 patients [initial mean refractive error: (-3.98 +/- 1.51) D]. Humphery Instruments ATLAS 8.0 was used for the computer-assisted analysis of corneal differential topographical maps. The examination of corneal topography was proceeded on the patients before the fitting of orthokeratology lenses and 6-month later. The distance from center of optic zone to apex of the cornea was measured as the value of decentration of orthokeratology lenses. The factors influenced the value of decentration were analyzed, including the initial refraction error, astigmatism, keratometry values, corneal eccentricity, and the diameter of the lens. The complaints of patients were recorded. Questionnaires, involving the symptoms of monocular diplopia and glare, were used to evaluate the effects of decentration of orthokeratology lenses on the visual function. RESULTS: The mean distance of decentration was (0.49 +/- 0.34) mm after one night fitting, the mean distance of decentration after follow-up for 1 month, 3 months and 6 months was (0.57 +/- 0.41) mm, (0.55 +/- 0.48) mm and (0.59 +/- 0.39) mm, respectively. After one month, the distance of decentration was less than 0.5 mm in 51.1% eyes, 0.5 - 1.0 mm in 35.6% eyes and more than 1.0 mm in 13.3% eyes.The direction of decentration in eyes with more than 0.50 mm decentration was mainly in the temporal side (48.5%). Patients with greater initial astigmatism and smaller diameter of lens showed greater distance of decentration (P < 0.05). There was no statistically significant difference in the distance of decentration between two groups with different corneal eccentricities and keratometry values (P > 0.05). The distance of decentration was greater in patients with monocular diplopia and glare. CONCLUSIONS: The degree of decentration of orthokeratology depends on the degree of initial refractive error, astigmatism and the design of orthokeratology lenses. The degree of decentration can influence the visual function.