Dupre Terin E, Benjamin William J
Vision Science Research Center (T.E.D., W.J.B.), University of Alabama, Birmingham, Birmingham, AL; and Material Performance Assessments, LLC (W.J.B.), Hoover, AL.
Eye Contact Lens. 2019 Jan;45(1):23-27. doi: 10.1097/ICL.0000000000000527.
The relationship between water (W) content and silicon (Si) content of silicone-hydrogel (SiHy) contact lens materials was inspected using identical methodologies, equipment, and operators for materials composing 16 types of commercially available SiHy contact lenses. Fluorine (F) content was included in the analysis for the three materials also containing a fluoropolymer. One type of lens consisted of a bulk SiHy material coated with thin layers of conventional hydrogel.
SiHy materials were obtained in the form of 16 contact lens brands purchased on the open market in a common range of refractive powers from -3 to +6 D in single lots. All test lenses were equilibrated at room temperature in a standard saline recommended in the American National Standards Institute Z80.20-2016 and International Organization for Standardization (ISO) 18369-4:2017 standards. W content was obtained gravimetrically, in %, according to those standards for 16 lenses of each SiHy material. Si content was determined in % using inductively coupled plasma optical emission spectroscopy for four digested lenses of each material. F content was determined in % using an ion-selective electrode for four combusted lenses of each of the three fluorinated SiHy materials. W and Si contents of the bulk SiHy material of the coated lens were estimated by computational exclusion of the hydrogel layers.
The linear coefficients of determination (R, n=16) were -0.7576 (relating mean dry Si content [n=4] to mean W content [n=16]) and -0.8819 (relating mean hydrated Si content [n=4] to mean W content [n=16]). When the 4 SiHy materials that were fluorinated or coated were excluded from the analysis, the R values (n=12) were -0.8869 and -0.9263, respectively. When F contents and the coating were added to the assessments, the linear coefficients of determination (R, n=16) became -0.8948 (relating mean dry [Si+F] content to mean W content) and -0.9397 (relating mean hydrated [Si+F] content to mean W content).
There is a fundamental negative linear relationship between Si and W contents for SiHy contact lens materials above 35% W content that is followed when F content and hydrogel coatings are empirically added to the analysis below 35% W content. The relationship was tightest for hydrated (Si+F) content and W content, for which the regression equation had an R of -0.9397: (Si+F)=-0.3073 (W)+22.148. The relationship between (Si+F) and W therefore seems to be based on composition rather than structure of available SiHy contact lens materials.
使用相同的方法、设备和操作人员，对16种市售硅水凝胶（SiHy）隐形眼镜材料中硅（Si）含量与水（W）含量之间的关系进行了检测。对于三种还含有含氟聚合物的材料，分析中纳入了氟（F）含量。有一种镜片由涂覆有传统水凝胶薄层的块状SiHy材料组成。
以16个隐形眼镜品牌的形式在公开市场上购得SiHy材料，其屈光力在-3至+6 D的常见范围内，均为单批次。所有测试镜片均在美国国家标准学会Z80.20 - 2016和国际标准化组织（ISO）18369 - 4:2017标准推荐的标准盐溶液中于室温下平衡。根据这些标准，通过重量法测定每种SiHy材料的16片镜片的W含量，以百分比表示。使用电感耦合等离子体发射光谱法测定每种材料的4片经消化镜片的Si含量，以百分比表示。使用离子选择电极测定三种含氟SiHy材料中每种材料的4片经燃烧镜片的F含量，以百分比表示。通过计算排除水凝胶层来估算涂覆镜片的块状SiHy材料的W和Si含量。
决定系数的线性系数（R，n = 16）分别为-0.7576（将平均干燥Si含量[n = 4]与平均W含量[n = 16]相关联）和-0.8819（将平均水合Si含量[n = 4]与平均W含量[n = 16]相关联）。当从分析中排除4种氟化或涂覆的SiHy材料时，R值（n = 12）分别为-0.8869和-0.9263。当将F含量和涂层添加到评估中时，决定系数的线性系数（R，n = 16）变为-0.8948（将平均干燥[Si + F]含量与平均W含量相关联）和-0.9397（将平均水合[Si + F]含量与平均W含量相关联）。
对于W含量高于35%的SiHy隐形眼镜材料，Si和W含量之间存在基本的负线性关系，当经验性地将F含量和水凝胶涂层添加到W含量低于35%的分析中时，该关系仍然成立。对于水合（Si + F）含量和W含量，该关系最为紧密，其回归方程的R为-0.9397：（Si + F）=-0.3073（W）+ 22.148。因此，（Si + F）与W之间的关系似乎基于现有SiHy隐形眼镜材料的组成而非结构。
