多焦点角膜接触镜配戴后角膜屈光力的变化及其与眼轴增长的相关性

目的：观察儿童配戴多焦点角膜接触镜前后角膜屈光力分布情况，并分析戴镜后角膜屈光力与眼轴增长的相关性。方法：回顾性系列病例研究。收集2018年12月至2019年4月在温州医科大学附属眼视光医院杭州院区视光诊疗中心就诊行多焦点角膜接触镜验配并完成1年随访的8～14岁儿童20例 （40眼）。使用Medmont测量双眼戴镜前及戴镜30 min后角膜形态，手动收集角膜各位点上的切向屈 光力。收集角膜4个轴方向（鼻侧：N；颞侧：T；上方：S；下方：I）及中央处角膜屈光力。4个方位均为距离角膜顶点1～3.5 mm范围，以0.5 mm为间隔，记录为N/T/S/I（1/1.5/2/2.5/3/3.5）；同时收集戴镜后4个方位角膜最大屈光力值及角膜顶点处屈光力，并收集同样位置戴镜前角膜屈光力值，记录为N/T/S/I（max）。将各位点角膜屈光力与角膜顶点屈光力的差值定义为相对周边屈光力，角膜最大屈光力值与角膜顶点屈光力差值定义为相对最大屈光力。使用IOLMaster测量初始及戴镜1年后双眼眼轴长度。使用线性回归分析角膜相对最大屈光力值及其改变量与眼轴改变量的相关性。结果： 角膜周边各位点屈光力较中央屈光力弱。戴镜后水平方向上，除了N2.5、N3及N3.5之外的位点，其余位点相对周边屈光力显著增加；垂直方向上，除了S3、S3.5及I3.5之外的位点，其余位点相对周边屈光力显著增加。配戴多焦点角膜接触镜1年后，眼轴增长（0.28±0.21）mm。戴镜后角膜相对最大屈光力较戴镜前显著增加，其中初始年龄及等效球镜度（OR=0.393，F=3.447，P=0.042）、戴镜前后 Imax改变量（OR=0.157，F=7.057，P=0.011）及戴镜后相对Imax（OR=0.108，F=4.583，P=0.039）对眼轴增长有显著影响。结论：配戴多焦点角膜接触镜后，由相对周边正屈光力朝正屈光力改变。除年龄及等效球镜度外，戴镜后下方角膜相对最大屈光力及戴镜前后相对最大屈光力改变量对眼轴增长有显著影响，推测与戴镜后显著减少眼球相对周边远视离焦量相关。

Correlation between Axial Length Growth and the Relative Corneal Power Shift after Using Multifocal Contact Lenses

Objective: To investigate the distribution of corneal refractive power before and after using multifocal contact lenses and to assess the relationship between corneal refractive power and axial elongation. Methods: A retrospective study was conducted on 40 eyes of 20 children from December 2018 to April 2019. The 8- to 14-year-old children were fitted with multifocal contact lenses in the Hangzhou Branchof Zhejiang Eye Hospital Affiliated to Wenzhou Medical University Corneal topography was measured by Medmont before and 30 minutes after using multifocal contact lenses. The corneal apical refractive power and corneal tangential power of multiple spots along the nasal, temporal, superior and inferior axes were manually collected. The range included 1 mm to 3.5 mm away from the apex in 0.5 mm steps and were recorded as N/T/S/I (1/1.5/2/2.5/3/3.5). At the same time, the corneal maximum refractive power and apical refractive power were manually collected after wearing the lenses. Corneal and apical refractive power were also collected at the same spots before wearing lenses and were recorded as N/T/S/I max. The difference between any corneal tangential power and corneal apical refractive power was defined as relative peripheral refractive power. The difference between any corneal maximum refractive power and apical refractive power was defined as relative maximum refractive power. The axial length was measured by IOLMaster before and 1 year after wearing the multifocal contact lens. Linear regression was used to analyze the relationship between the relative maximum refractive power and axial elongation. Results: The corneal peripheral refractive power was weaker than the corneal apical refractive power. After multifocal contact lens treatment, the relative peripheral refractive power was significantly increased at the horizontal axes, except at the N2.5, N3 and N3.5 spots. The relative peripheral refractive power was significantly increased at the vertical axes, except at the S3, S3.5 and I3.5 spots. Mean axial elongation at 1 year was 0.28±0.21 mm. The corneal relative maximum refractive power significantly increased after wearing the lens. The initial age and spherical equivalent refractive error (OR=0.393, F=3.447, P=0.042), inferior corneal relative maximum refractive power changes (OR=0.157, F=7.057, P=0.011) and the relative maximum refractive power after wearing the lens (OR=0.108, F=4.583, P=0.039) had significant effects on axial elongation during the 1-year period. Conclusions: The corneal relative peripheral negative refractive power changes to positive refractive power after wearing multifocal contact lens. Besides the initial age and spherical equivalent refractive error, after multifocal lens treatment, the relative maximum refractive maximum refractive power and the changes have significant effects on axial elongation. It was expected to be correlated with a significant reduction in the relative peripheral hyperopia defocus after wearing the lens.