Young Graeme, Hall Lee, Sulley Anna, Osborn-Lorenz Kathrine, Wolffsohn James S
*PhD, FCOptom, FAAO †BSc, PhD ‡BSc, MCOptom, FAAO §OD, MS, FAAO ∥MBA, PhD, FAAO Visioncare Research Ltd, Farnham, United Kingdom (GY, LH); Aston University, Birmingham, United Kingdom (GY, LH, JSW); Johnson & Johnson Vision Care Companies, Wokingham, United Kingdom (AS); and Johnson & Johnson Vision Care Companies, Jacksonville, Florida (KO-L).
Optom Vis Sci. 2017 Apr;94(4):458-465. doi: 10.1097/OPX.0000000000001048.
To evaluate the inter-relationship of soft contact lens base curve radius (BC), diameter, and lens fit using a mathematical model.
A spreadsheet mathematical model was used to evaluate theoretical fitting characteristics for various combinations of soft lens BC and diameter. The designs were evaluated using ocular topography data collected from 163 UK subjects. The model evaluated lens tightness (edge strain) and on-eye diameter (horizontal corneal overlap) and assumed that acceptable values fell within the range 0 to 6% and 0.2 to 1.2 mm, respectively. Analyses were undertaken of various trends relating to soft lens fit, including (1) the effect of BC and diameter on fitting success; (2) the effect of lens asphericity, BC, and sag on lens diameter on the eye; and (3) the effect of lens diameter on lens tightness.
The highest overall success rate (90.2%) was achieved with an 8.60/14.2 mm (BC/diameter) design. Using this design on the sample population, the median edge strain value was 3.2% (IQR: 2.1%) whereas median corneal overlap was 0.62 mm (IQR: 0.35). There was a positive correlation (r = 0.37, P < .0001) between edge strain and corneal overlap. Edge strain showed significant correlations with each of the ocular topography variables, most notably corneal asphericity (-0.62, P < .0001). Corneal overlap showed significant correlations with corneal asphericity (r = -0.42, P < .0001) and corneal diameter (r = 0.92, P < .0001). For a 0.4 mm change in BC, it is necessary to change diameter by 0.2 mm to maintain similar on-eye diameter (arclength). When changing lens diameter, a change in BC of 0.2 mm is required to maintain similar tightness of fit.
Mathematical modeling is a useful technique for large-scale evaluation of the interactions of soft contact lens design and fit. The study has given useful insights into the general performance of soft lens designs.
使用数学模型评估软性接触镜基弧半径（BC）、直径和镜片适配之间的相互关系。
使用电子表格数学模型评估软性镜片BC和直径各种组合的理论适配特征。采用从163名英国受试者收集的眼表地形图数据对这些设计进行评估。该模型评估镜片贴合度（边缘应变）和眼上直径（角膜水平重叠），并假设可接受值分别在0%至6%和0.2至1.2毫米范围内。对与软性镜片适配相关的各种趋势进行了分析，包括：（1）BC和直径对适配成功的影响；（2）镜片非球面度、BC和矢高对眼上镜片直径的影响；（3）镜片直径对镜片贴合度的影响。
8.60/14.2毫米（BC/直径）设计的总体成功率最高（90.2%）。在样本群体中使用该设计时，边缘应变的中位数为3.2%（四分位距：2.1%），而角膜重叠的中位数为0.62毫米（四分位距：0.35）。边缘应变与角膜重叠之间存在正相关（r = 0.37，P <.0001）。边缘应变与每个眼表地形图变量均显示出显著相关性，最显著的是角膜非球面度（-0.62，P <.0001）。角膜重叠与角膜非球面度（r = -0.42，P <.0001）和角膜直径（r = 0.92，P <.0001）显示出显著相关性。对于BC变化0.4毫米，需要将直径改变0.2毫米以维持相似的眼上直径（弧长）。当改变镜片直径时，需要将BC改变0.2毫米以维持相似的贴合紧密度。
数学建模是大规模评估软性接触镜设计与适配相互作用的有用技术。该研究为软性镜片设计的总体性能提供了有益见解。
