University of Liverpool, Liverpool, United Kingdom.
University of Toronto, Toronto, Canada.
PLoS One. 2019 May 14;14(5):e0216484. doi: 10.1371/journal.pone.0216484. eCollection 2019.
To evaluate the impact of soft contact lens eye-fit on optical power by computational modelling and to produce correction maps for reversing this impact during the design process.
Finite element models of spherical and toric hydrogel contact lenses at varying nominal powers of -20 D to +20 D, base curves radii (R1b) of 8.2, 8.5, 8.8 mm, and overall diameters (d3) of 14.5, 15.0, 15.5 mm were generated. Lenses were fitted to computational eye models generated with human eyes' topography data. Combined eye-lens simulations were run under the boundary conditions of the tears' surface tension between the contact lens and the eye in addition to the eyelid blink pressure. Lens optical zone power changes were calculated through computational light-ray tracing methods following each simulation.
Effective power changes (EPC) were affected negatively for all toric simulated lenses with power varying from -20 D to +20 D. Spherical lenses demonstrated similar behaviour, however with some positive EPC over the power range from -20 D to -10 D for spherical power (SPH) lenses. EPC assessment was between +0.25 D and -0.5 D for most lenses, however, lenses with prescriptions from +10 D to +20 D incurred EPC outside this range. The spherical lenses showed a maximum effective power change of +1.046 ± 0.338 D (Average Eye), and a minimum of -3.278 ± 0.731 D (Steep Eye). Similarly, the toric lenses showed a maximum of +1.501 ± 0.338 D (Average Eye), and a minimum of -3.514 ± 0.731 D (Steep Eye). EPC trends, along with minimum and maximum power, generally increased negatively as nominal lens prescription increased positively. Contact lens base curve selection affected the assessed effective power change for both spherical and toric lenses. The effect from lens total diameter for spherical lenses was less substantial than that for toric lenses.
This study considered the impact of soft contact lens design parameters on effective optical power changes (EPC) after eye-fit. Spherical lenses experienced more EPC of clinical significance (>0.25 D) than toric lenses. Both types of lenses, spherical and toric (simple astigmatism), demonstrated similar trends in EPC on fitting from -20 D to +20 D, with lenses in the extremely positive and the extremely negative prescriptions demonstrating the highest EPCs. The lens base curve impacted the extent of EPC observed, with flatter base curves experiencing less power change. Diameter proved to impact toric lenses more than spherical ones, however generally the diameter has less effect on power change than base curve selection.
通过计算建模评估软镜适配对光焦度的影响，并在设计过程中生成校正图以逆转这种影响。
生成了名义屈光度为-20 D 至+20 D、基弧半径（R1b）为 8.2、8.5、8.8 mm 和总直径（d3）为 14.5、15.0、15.5 mm 的球形和散光水凝胶接触镜的有限元模型。将镜片拟合到使用人眼地形图数据生成的计算眼睛模型上。在接触镜和眼睛之间的泪液表面张力以及眼睑眨眼压力的边界条件下，对组合的眼睛-镜片模拟进行了运行。通过计算光线跟踪方法计算了每个模拟后的镜片光学区功率变化。
所有模拟的散光镜片的有效功率变化（EPC）都受到负向影响，其屈光度从-20 D 变化到+20 D。球形镜片表现出类似的行为，但对于球形镜片的-20 D 至-10 D 屈光度范围，EPC 有些为正。对于大多数镜片，EPC 评估在+0.25 D 和-0.5 D 之间，但是，处方从+10 D 到+20 D 的镜片的 EPC 超出了该范围。球形镜片的最大有效功率变化为+1.046 ± 0.338 D（平均眼），最小为-3.278 ± 0.731 D（陡眼）。同样，散光镜片的最大有效功率变化为+1.501 ± 0.338 D（平均眼），最小为-3.514 ± 0.731 D（陡眼）。随着名义镜片处方的增加，EPC 趋势、最小和最大功率通常呈负向增加。接触镜基弧的选择会影响球形和散光镜片的评估有效功率变化。对于球形镜片，镜片总直径的影响小于散光镜片。
本研究考虑了软接触镜设计参数对眼适配后有效光学功率变化（EPC）的影响。球形镜片的 EPC 临床意义大于散光镜片（>0.25 D）。从-20 D 到+20 D 拟合时，两种类型的镜片（球形和散光（单纯散光））的 EPC 都表现出相似的趋势，处方极高和极低的镜片表现出最高的 EPC。镜片基弧影响观察到的 EPC 程度，基弧越平坦，功率变化越小。直径对散光镜片的影响大于球形镜片，但总体而言，直径对功率变化的影响小于基弧选择。
