Purpose

To measure the refractive index (RI) of commonly available soft contact lens (CL) materials, their packaging solutions and compare to the manufacturers’ nominal RI. The relationship between RI versus water content, and the effect of inaccurate RI when converting lens power measured in solution to in-air back vertex power were examined.

Methods

The RI of 18 single vision soft CL materials were measured using CLR 12–70 digital refractometer. Three lenses of each material were measured, in their packaging solution and then after soaking in standard phosphate buffered saline (PBS). The RIs of packaging solution were also measured. Accuracy requirements for correct wet to dry power conversion based on thick lens formula were projected.

Results

The standard deviation between three samples was less than 0.005. The measured RI ranged from 1.3744 ± 0.001–1.4265 ± 0.0004 for PBS soaked and from 1.3739 ± 0.0003–1.4264 ± 0.0024 for packaging solution soaked materials. Comparing nominal with mean measured PBS and packaging solution RIs, 5 and 3 lens materials, respectively, fell outside ISO tolerance. The packaging solution RI of DailiesAquaComfortPlus had the largest difference of 0.0040, compared to RI of standard PBS. For converting lens power measured in PBS to in-air power, the difference between measured and nominal RI of 0.0104 would result in wrongly calculated in-air power 0.99 D for a -6.00 D lens.

Conclusion

The CLR 12–70 is reliable and accurate refractometer for the measurement of soft CL materials. Accurate RI measurements are of relevance with increased use of wavefront sensors to measure lens power while they are immersed in solution. Even small errors in solution or material RI can lead to significant errors in converted in-air power. To obtain valid in-air lens power results, measurement conditions must match the material and solution RIs used for the conversion.

中文翻译：

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在包装溶液和标准磷酸盐缓冲盐水中测量的软性隐形眼镜材料的折射率及其对后顶焦度计算的影响。

目的

要测量常用软接触镜（CL）材料及其包装解决方案的折射率（RI），并与制造商的标称RI进行比较。检查了RI与水含量之间的关系，以及将溶液中测得的镜片光焦度转换为空气中后顶焦度时RI不准确的影响。

方法

使用CLR 12–70数字折光仪测量了18种单视觉软CL材料的RI。在包装溶液中，然后在标准磷酸盐缓冲盐水（PBS）中浸泡后，测量每种材料的三个镜片。还测量了包装溶液的RI。预测了基于厚透镜公式正确进行干湿转换的精度要求。

结果

三个样品之间的标准偏差小于0.005。对于浸透的PBS，测得的RI范围为1.3744±0.001–1.4265±0.0004，对于浸透包装的材料，测得的RI为1.3739±0.0003–1.4264±0.0024。将标称值与平均测得的PBS和包装溶液RI进行比较，分别有5种和3种镜片材料超出了ISO公差。与标准PBS的RI相比，DailiesAquaComfortPlus的包装溶液RI的差异最大为0.0040。为了将在PBS中测得的镜片光焦度转换为空中光焦度，对于-6.00 D镜片，实测RI与标称RI之间的差0.0104将导致错误计算的空中光焦度0.99D。

结论

CLR 12–70是用于测量软CL材料的可靠，准确的折光仪。准确的RI测量与将波前传感器浸入溶液中时用于测量透镜光焦度的方法越来越重要。溶液或材料RI的即使很小的误差也可能导致转换后的空中功率出现重大误差。为了获得有效的空中透镜放大率结果，测量条件必须与用于转换的材料和溶液RI匹配。