标准编号:	GB/T 11417.7-2012
中文名称:	眼科光学 接触镜 第7部分: 理化性能试验方法
英文名称:	Ophthalmic optics. Contact lenses. Part 7: Physicochemical properties test methods
中标分类:	C40    医用光学仪器设备与内窥镜
行业分类:	GB    国家标准
ICS分类:	11.040.70 11.040.70    眼科设备 11.040.70
发布机构:	中华人民共和国国家质量监督检验检疫总局 中国国家标准化管理委员会
发布日期:	2012-12-31
实施日期:	2013-6-1
标准状态:	被替代
被新标准替代:	GB/T 11417.7-2012/XG1-2022 《眼科光学 接触镜 第7部分: 理化性能试验方法》含国家标准第1号修改单
被替代日期:	2013-6-1
翻译语言:	英文
文件格式:	PDF
中文字符数:	25000 字
翻译价格(元):	1800.00 元
交付时间:	付款后 1 个工作日

Ophthalmic Optics—Contact Lenses—

Part 7: Physicochemical Properties

Test Methods

眼科光学 接触镜

第7部分：理化性能试验方法



1 Scope



GB/T 11417.7 specifies the test methods of physicochemical properties for contact lenses materials, including extraction, oxygen permeability, refractivity, moisture content and contact angle.

This part is applicable to the test of physicochemical properties for contact lenses.



2 Normative References



The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated reference, the latest edition (including any amendment) applies.

GB/T 6682-2008 Water for Analytical Laboratory Use—Specification and Test Methods

GB/T 11417.1-2012 Ophthalmic Optics—Contact Lenses—Part 1: Vocabulary, Classification System and Recommendations for Labeling Specifications

GB 11417.2-2012 Ophthalmic Optics—Contact Lenses—Part 2: Rigid Contact Lenses

GB 11417.3-2012 Ophthalmic Optics—Contact Lenses—Part 3: Soft Contact Lenses

GB/T 11417.4-2012 Ophthalmic Optics—Contact Lenses—Part 4: Standard Saline Solution for Testing

GB/T 11417.6-2012 Ophthalmic Optics—Contact Lenses—Part 6: Testing Methods for Mechanical Properties



3 Terms and Definitions



For the purposes of this part, the terms and definitions given in GB/T 11417.1-2012 apply.



4 Physicochemical Properties of Contact Lenses



4.1 Test Methods, Unit and Repeatability

The physicochemical properties of hydrogel and non-hydrogel materials for contact lenses, as listed in Table 1, are measurable. The appropriate test methods, unit and repeatability are also specified in Table 1. If other test method is applied, the following requirements shall also be met.

Table 1 Test Methods, Unit and Repeatability of Physicochemical Properties

Item Repeatability Measuring unit Test method

Extraction b Mass fraction 4.2

Oxygen permeability 10% Dk unit a 4.3

Refractivity 0.01 Dimensionless 4.4

Moisture content 2% (Absolute value) % 4.5

Contact angle 2° (°) 4.6

a The unit of Dk is 10-11(cm2/s)[mLO2/(mL·hPa)].

b According to the terms and definitions given in GB/T 11417.1-2012, the repeatability of such test results shall be set by independent laboratory.

4.2 Extraction

4.2.1 Overview

It is a standard method that the extractable substance of contact lenses material is measured quantitatively by Soxhlet extraction method with different solvents. With the lenses dried to be constant, the mass difference of lenses before and after extraction at the dry state is the mass of extractable substance.

The quantitative and qualitative analysis of extractable substance contributes to assessing the new materials of contact lenses and the determination of preclinical inspection procedure. The extracted substance of lenses is measured by appropriate chromatography, spectrophotometry and wet analysis, thus to determine the content of residual monomer, crosslinking agent and initiating agent in the polymerization process.

4.2.2 Principle

The ordinary Soxhlet extractor is applied to this method. Water and an appropriate organic solvent at least shall be adopted in extraction. The solvent's effect on the lenses material substrate shall be considered for selection of organic solvent. Theoretically, the solvent shall not make the lenses material swelling or degraded. However, for the newly developed contact lenses materials, a solvent that can lead to reversible swelling may provide valuable information for overtime extraction.

4.2.3 Apparatus

The standard borosilicate glass Soxhlet extractor (See Figure 1) consists of round-bottom flask (100mL as recommended), Soxhlet extraction tube (30mL as recommended), condenser and heating jacket. Porous stainless steel sheet, sintered glass, filter paper or similar material with glass cotton plug or tube sleeve composed of other appropriate hermetic materials, as well as a vacuum drying oven or similar drying apparatus and an analytical balance of 0.1mg in precision are also needed.



Figure 1 Extraction Apparatus

4.2.4 Reagents

Distilled or deionized water that conforms to Level III requirements of GB/T 6682-2008 shall be adopted. Analytically pure or superior organic solvents shall be adopted (see Table 2). Laboratory-grade zeolite or anti-bumping particles shall be adopted. Appropriate drying agent shall be selected according to the properties of the tested material.

Table 2 Guidelines for Selection of Solvent for Lenses Extraction

Material Solvent Extraction

Hydrogel material Water (distilled or deionized)

N-hexane

Ethanol or methanol

Methylene chloride or chloroform Mild extraction (simulating intraocular extraction)

Slight extraction (nonpolar solvent)

Extraction of most non-crosslinking materials (may lead to swelling and degradation of lenses material)

Extraction of all non-crosslinking materials (may lead to swelling and slight degradation of lenses material)

Rigid lenses and polysiloxane elastic materials Water (distilled or deionized)

N-hexane

Methylene chloride or chloroform Mild extraction (simulating intraocular extraction)

Slight extraction (nonpolar solvent)

Extraction of all non-crosslinking materials (may lead to swelling and slight degradation of lenses material)

4.2.5 Test sample

The test sample shall be able to represent the finished product. It shall be packed in accordance with the finished contact lenses. The specimen shall be processed as per the routine manufacturing process of the product. The sample for lenses to be subject to sterilization treatment shall be treated likewise during preparation. Sufficient lenses shall be taken to ensure that the total dry mass of lenses sample is not less than 200mg before extraction.

The hydrogel lenses are generally placed in the solution containing inorganic salt. If water is used as extraction solvent, to reduce the impact of inorganic salt on the test result, appropriate adjustment shall be made in calculation and the moisture content of lenses shall also be determined, so as to accurately figure out the impact of inorganic salt on the extractable substance. Otherwise, immerse the specimen in water at room temperature before the test and change the water twice at least at an interval of 24h to reach equilibrium.

4.2.6 Test procedure

It is preferred to dry the specimen to be constant in the vacuum state at 60℃±5℃. Before weighing, cool the specimen to room temperature in the vacuum state or in a closed container containing active drying agent and then weigh to the nearest of ±0.1mg (m1). Put the specimen in the extraction sleeve and add appropriate solvent into the flask about 70% of its capacity (the solvent is selected in Table 2). Zeolite may be added into the flask if necessary. Put the round-bottom flask on the heating jacket, insert the extraction sleeve in the Soxhlet extractor, then connect the extractor to the flask and insert the condenser at the top. If extremely volatile or inflammable solvent is used, the complete device shall be placed in the ventilated chamber.

Connect with the water source and start heating and extract for 4h at least. After the solvent is cooled to room temperature, take out the specimen from the extraction sleeve. Dry the specimen according to the above method and weigh to the nearest of ±0.1mg (m2).

Note: the extraction rate is recommended to be 4~6 times/h.

4.2.7 Calculation of result

The amount of extracted material shall be expressed in mass fraction (%), see Formula (1):

(1)

Where,

m1—the specimen mass before extraction;

m2—the specimen mass after extraction.

4.2.8 Test report

It shall cover Chapter 5 and the following items:

a) the composition of the original hydration solution;

b) statement that whether the obtained percentage of extractable substance is adjusted according to the salt content in hydration solution;

c) whether the specimen is equilibrated in water before the test.

4.3 Oxygen Permeability

4.3.1 Overview

The oxygen permeability of contact lenses materials may be determined by two standard methods, of which the common elements are listed in 4.3.2. 4.3.3 specifies the requirements of polarography which are applicable to all materials with the measuring range of 0~145. 4.3.4 specifies the requirements of coulometry which is applicable to non-hydrogel materials. The calibration of both methods is detailed in 4.3.5 and the report requirements in 4.3.6. If other methods for measuring the oxygen permeability are deviated from the standard method, they may be applied after such deviation is calibrated.

The oxygen permeation rate of several sample materials for contact lenses is measured initially, so as to determine the oxygen permeability. The errors, although possibly induced in measuring the oxygen permeation rate, may be effectively reduced (corrected) by taking a derivative of oxygen permeability. Therefore, after such errors are corrected, the oxygen permeability derived from the initial (uncorrected) oxygen permeation rate is very practical and convenient. Then the corrected oxygen permeation rate is calibrated.

4.3.2 Common elements of both methods

4.3.2.1 Parameters

According to the terms and definitions given in GB/T 11417.1-2012, the key parameters for measurement and derivation of oxygen permeation rate are oxygen flow (j), oxygen permeation rate, oxygen permeability, thickness (e.g. radial thickness) and harmonic mean thickness.

If coulometry is applied, j is obtained by the oxygen rate flowing through the Coulomb probe (μLO2/s) divided by the area (A). If polarography is applied, j is obtained by the difference between the measured current and dark current multiplied by the coefficient in Formula (2) and then divided by cathode area.

Thickness t is the radial thickness at the measuring point or the harmonic mean thickness in the measurement area. According to the measured central thickness and the known refractivity, back vertex center curvature radius and back vertex power, the harmonic mean thickness is calculated. Unless otherwise specified, the unit of t should be in centimeters.

For coulometry, Dk is obtained by the measured oxygen permeation rate Dk/t multiplied by the sample thickness t. For polarography, the oxygen permeation rate is corrected by adjusting the oxygen coverage and the gradient 1/Dk is obtained from the curve of the measured oxygen resistance t/Dk versus thickness t. The oxygen permeability is a physical property of material rather than a function of the material sample from or thickness.

For coulometry, Dk/t is obtained by the oxygen flow j divided by the oxygen pressure difference of sample at both sides (local oxygen pressure). For polarography, the oxygen permeability is obtained by the oxygen permeation rate corrected by the fringe and interlayer multiplied by the central thickness t. The oxygen permeation rate is a characteristic value of lenses material and lenses thickness, which depends on the design of lenses.

4.3.2.2 Test sample

This part can be used to determine the oxygen permeability of finished lenses made from hydrogel and non-hydrogel elastic materials, and also to determine that of standard lenses made from hydrogel and non-hydrogel elastic materials.

If the study is to determine the oxygen permeability of finished lenses by measuring the initial oxygen permeation rate, the harmonic mean thickness of the central plane where the contact lenses are exposed to oxygen flow (see 4.3.2.1) shall be indicated in the test report (see 4.3.6). This thickness is independent of the initial oxygen permeation rate [see Formula (2) or Formula (10)].

The radius of back optical area of the test sample is not required, which may be flat sample or range from 7.00mm~9.00mm. The diameter of back/front optical area shall be greater than the chord diameter of the tested central area for gas exchange (2h in diameter at cathode). The test sample surface shall be clean and the polishing quality shall be consistent with the lenses normally used for human.

For hydrogel materials, the sample shall be kept in the standard saline solution (refer to GB/T 11417.4-2012) at room temperature (20℃±2.0℃) for at least 24h prior to the test and shall be equilibrated for at least 2h at the equivalent eye temperature (35℃±0.5℃).

4.3.3 Polarography

4.3.3.1 General

This part introduces the determination of oxygen permeability for hydrogel and non-hydrogel, as well as rigid and elastic contact lenses materials by polarographic oxygen probe. The measuring method and testing conditions are given in the procedure.

Polarography is applicable to the determination of the corrected oxygen permeability (Dk) of rotational symmetric geometrical lenses with various focal powers and that of finished lenses made from rigid and non-hydrogel elastic materials, as well as that of standard lenses made from hydrogel and non-hydrogel, rigid elastic contact lenses materials.

4.3.3.2 Principle

After oxygen molecules pass through the material, the polarography can remove them immediately from the solution by electrochemical process, thus to directly measure the oxygen molecular diffusivity of a single test material. If an oxygen molecule separated out from the sample contacts with the central electrode (cathode) of oxygen sensor covering the back surface of sample, it will immediately convert into four hydrogen ions by electrochemical process. The generated ions, which are in proportion to the moving oxygen molecule, form a current that can be measured with apparatus. The initial (uncorrected) oxygen permeation rate is calculated by substituting the measured current into Formula (2), in mLO2/(A·s).

Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Physicochemical Properties of Contact Lenses
4.1 Test Methods, Unit and Repeatability
4.2 Extraction
4.3 Oxygen Permeability
4.5 Moisture Content
4.6 Contact Angle
5 Test Report

服科光学 接触镜
第7部分：理化性能试验方法
1 范围
GB/T 11417.7给出了接触镜材料理化特性的试验方法，包括了萃取、透氧系数、折射率、含水量和接触角。
本部分适用于接触镜理化性能的测试。
2规范性引用文件
下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新本版本(包括所有的修改单)适用于本文件。
GB/T 6682—2008分析实验室用水规格和试验方法
GB/T 11417.1—2012眼科光学 接触镜 第1部分：词汇、分类和推荐的标识规范
GB 11417.2—2012眼科光学 接触镜 第2部分：硬性接触镜
GB 11417.3—2012 眼科光学 接触镜 第3部分：软性接触镜
GB/T 11417.4—2012眼科光学 接触镜 第4部分：试验用标准盐溶液
GB/T 11417.6—2012眼科光学 接触镜 第6部分：机械性能试验方法
3术语和定义
GB/T 11417.1—2012中界定的术语和定义适用于本文件。
4接触镜的理化特性
4.1试验方法、单位、重复性
表1中列出已应用于制作接触镜的水凝胶和非水凝胶材料的理化特性是可测的。另外，表1中给出了这些特性的试验方法、单位、重复性。若采用其他试验方法，也应遵守以下规定。
表1 理化特性试验方法、单位、重复性
项目 重复性 测量单位 试验方法
萃取 b 质量分数 4.2
透氧系数 10％ Dk单位a 4.3
折射率 0.01 无量纲 4.4
含水量 2％(绝对值) ％ 4.5
接触角 2° (°) 4.6
a Dk的单位是10-11(cm2/s)[mLO2/(mL·hPa)]。
b 根据GB/T 11417.1—2012中的术语和定义，这些测试结果的重复性应由独立实验室建立。

4.2萃取
4.2.1 概述
采用不同溶剂，通过索氏萃取法定量测定接触镜材料可萃取物是一种标准方法。将镜片干燥至恒重，萃取前后镜片在干燥状态下的质量之差即为镜片可萃取物质的质量。
对于可萃取物质定量和定性的分析有助于对接触镜片新材料进行评价，同时也有助于确定临床前的检查程序。通过合适的色谱法、光度法以及湿法分析来测定镜片萃取出的物质，从而确定聚合过程中残留单体、交联剂和引发剂含量。
4.2.2原理
本方法使用的是普通的索氏萃取器。萃取中要选用水和至少一种合适的有机溶剂。在选用有机溶剂时，要考虑到溶剂对镜片材料基质的影响。理论上溶剂不应致使镜片材料产生膨胀或降解。然而，对于新研发的接触镜材料，选择一种使其产生可逆溶胀的溶剂将为超时萃取的可能提供有价值的信息。
4.2.3仪器
标准的硼硅酸盐玻璃索氏萃取器(见图1)由圆底烧瓶(建议100 mL)，索氏萃取管(建议30 mL)，冷凝器和加热套组成。还需使用多孔不锈钢板、烧结玻璃、滤纸或类似带有玻璃棉塞的材质或其他合适密闭材料组成的管套，同时需一个真空干燥箱或类似的干燥仪器和一个具有0.1 mg精度的分析天平。

图1萃取仪器
4.2.4试剂
应采用符合GB/T 6682—2008中三级要求的蒸馏水或去离子水。应采用分析纯或更高级别的有机溶剂(见表2)。应采用实验室级沸石或防暴沸颗粒。根据被测材料的特性选用合适的干燥剂。
表2 镜片萃取用溶剂的选用指导
材料 溶剂 萃 取
水凝胶材料 水(蒸馏水或去离子水)正己烷乙醇或甲醇二氯甲烷或氯仿 温和萃取(模拟眼内萃取)轻微萃取(非极性溶剂)萃取多数非交联材料(但可能会引起镜片材料溶胀和降解)萃取所有非交联材料的(但可能会引起镜片材料溶胀和轻微降解)
硬性镜片和聚硅氧烷弹性材料 水(蒸馏水或去离子水)正己烷二氯甲烷或氯仿 温和萃取(模拟眼内萃取)轻微萃取(非极性溶剂)萃取所有非交联材料(但可能会引起镜片材料溶胀和轻微降解)

4.2.5测试样片
测试样片应能代表成品片。应按照接触镜成品状态包装。试样的加工应与其产品的常规制造过程一致。须经灭菌处理的镜片在样品制备时也需同样处理。抽取足够量的镜片，确保镜片样品在萃取之前的总干质量不少于200 mg。
水凝胶镜片通常是置于含有无机盐的溶液中。当用水作为萃取溶剂时，为减少无机盐对测试结果的影响，应在计算时做出适当的调整，还需了解镜片的含水量，从而能精确计算出无机盐对可萃取物的影响。否则，在测试开始前，要将试样在室温下的水中浸泡，中间至少换水两次，每隔24 h换水一次，以达到平衡。
4.2.6测试步骤
在60℃±5℃温度下，最好在真空状态中，将试样干燥至恒重。称重前试样在真空状态中或含活性干燥剂的密闭容器中冷却至室温，称重精确至±0.1 mg(m1)。将试样放入萃取套管中，向烧瓶加入体积约为其容量70％的合适溶剂(溶剂选用见表2)。如需要，可在烧瓶中放入沸石。将圆底烧瓶放在加热套上，萃取套管插入索氏抽提器中，然后再将抽提器与烧瓶连接，在其顶部插入冷凝器。当使用极易挥发或易燃溶剂时，整个装置应置于通风柜中。
接通水源并开始加热，萃取应至少进行4 h。当溶剂冷却至室温后，从萃取套管中取出试样。按上述方法干燥试样，称重精确至±0.1 mg(m2)。
注：萃取速率建议为4次/h～6次/h。
4.2.7结果计算
萃取材料的量应表述为质量分数(％)，见公式(1)：
…………………………(1)
式中：
m1——萃取前试样质量；
m2——萃取后试样质量。
4.2.8测试报告
应包含第5章和以下内容：
a)最初水合溶液的成分；
b)指明是否根据水合溶液中的盐分含量，对所得到的可萃取物百分比进行调整；
c)本试验前试样是否在水中进行平衡。
4.3透氧系数
4.3.1 概述
接触镜材料透氧系数的测定有2种标准方法，在4.3.2中列出了它们的共同要素。在4.3.3中给出了极谱法要求，它适用于所有材料，测量范围为0～145。在4.3.4中给出了库仑法的要求，它适用于非水凝胶材料。2种方法的校准见4.3.5，在4.3.6中给出了报告要求。当采用其他方法测量透氧系数与标准方法有偏离时，需在这些偏离被校准后方可应用。
初级测量几个接触镜试样材料的透氧量，从而测定透氧系数。虽然在测量透氧量时可能会产生某些误差，通过对透氧系数求导能有效减少误差(修正)。因此对这些误差进行修正后，从初级(无修正)透氧量测量求导透氧系数是非常实用和方便的。然后对修正的透氧量值进行校准。
4.3.2方法的共同要素
4.3.2.1参量
参见GB/T 11417.1—2012中的术语和定义，测量和透氧量求导的重要参量是氧流量(j)、透氧量、透氧系数和厚度(如径向厚度)和调和平均厚度。
当采用库仑法时，j等于流过库仑探头氧气的速率(μLO2/s)除以该面积(A)。当采用极谱法时，j是实测电流与暗电流的差值乘上公式(2)中的系数，然后除以阴极面积。
厚度t是测点的径向厚度或测量区域的调和平均厚度。通过测量中心厚度和已知的折射率，后顶中心曲率半径和后顶焦度，计算得到调和平均厚度，除非有其他指定，t的单位宜为厘米。
当采用库仑法时，Dk等于测得的透氧量Dk/t乘上样品厚度t。当采用极谱法时，透氧量通过调整氧流过面积来修正，从测量的氧阻t/Dk与厚度t的曲线得到斜率1/Dk。透氧系数是材料的物理特性，不是材料样品形状或厚度的函数。
当采用库仑法时，Dk/t等于氧流量j除以样品两边氧压差(氧局部压力)。当采用极谱法时，透氧系数是通过边缘和界层修正的透氧量，乘上中心厚度t。透氧量是镜片材料和镜片厚度的特性值，取决于镜片的设计。
4.3.2.2测试样品
本部分可用于测定水凝胶和非水凝胶弹性材料成品片的透氧系数。同样也可用于测定水凝胶和非水凝胶弹性材料标准片的透氧系数。
如果研究的目的是通过测量初级透氧量来测定成品镜片透氧系数，应在测试报告(见4.3.6)中给出接触镜与氧流量量(见4.3.2.1)接触中心面上的调和平均厚度。这个厚度与初级透氧量无关[见公式(2)或式(10)]。
测试样品的后光学区域半径无要求，可为平板样品，也可从7.00 mm～9.00 mm范围内变化。后、前光学区域直径应大于用于气体交换的被测中心区域的弦直径(阴极直径2 h)。测试样品表面应清洁，且抛光质量应与人正常使用镜片产品一致。
对于水凝胶材料，在测试前，样品应保存在室温(20℃±2.0℃)下在标准盐溶液(参照GB/T 11417.4—2012)至少24 h，并且在等效眼温度(35℃±0.5℃)下至少平衡2 h。
4.3.3极谱法
4.3.3.1 总则
本部分给出了使用极谱氧探头测定水凝胶和非水凝胶，硬性和弹性接触镜材料的透氧系数。步骤中给出了测量方法和测试条件。
极谱法适用于测量各种光焦度和旋转对称几何镜片，硬性和非水凝胶弹性材料成品片的修正透氧系数(Dk)，同样适用于测定水凝胶和非水凝胶，硬性和弹性接触镜材料标准片的修正透氧系数。
4.3.3.2原理简述
当氧分子透过材料时，极谱法可通过电化法将它们从溶液中瞬间去除，从而直接测量透过一片测试材料的氧分子扩散数。当从样品中分离出一个氧分子，它与覆盖着样品的后表面的氧传感器中心电极(阴极)接触，瞬间电化转化成4个氢离子。产生的离子形成仪器可测量的电流，它与移动的氧分子成比例。测得的电流代入式(2)计算初级(非修正)透氧量，单位为mLO2/(A·s)
…………………………(2)
式中
pA——大气压减水汽压的差乘以0.209(大气中氧气含量百分比值)，hPa；
A——探头中心电极(阴极)的面积，cm2；
I——安培表测得的电流值，A；
Id——探头暗电流(无氧的电流)，A。
在标准温度和压力下，假定每个氧分子减少需要4个电荷，1千克摩尔除以法拉第常数，除以每个氧分子减少所需的电荷数，得到的值为常数5.804×10-2。
为了导出特定材料的透氧系数，应进行边缘效应修正(见4.3.3.3)和界层效应修正(见4.3.3.4)。只有这样才能计算得到符合GB 11417.2—2012和GB 11417.3—2012中的接触镜材料的修正透氧量。
4.3.3.3边缘效应修正
在所有扩散方法中都有的效应是“边缘效应”。当氧从样品的一个表面通过材料另一面是不连续的，材料的横截面会发生边缘效应。在极谱法中，氧从样品比较大的前表面穿过，最终接触到镜片后面的阴极，因为前表面大于阴极面积，氧穿过镜片的前表面，像流过漏斗一样汇集到阴极。实际上，公式(2)中的A被低估，氧流量不再符合上面给出的阴极面积的线性函数。但是，如果阴极面积和样品厚度的比值是在仪器给出的校准范围中时，可用一个相对简单的计算方法修正边缘效应，精度符合本标准要求。
在4.3.3.4中需要用到透氧量的倒数，需要对初级倒数值(t/Dk或阻率)进行边缘效应修正。可采用适用的公式(3)、式(4)、式(5)、式(6)修正初级t/Dk值。在下式中，t和阴极直径D的单位为mm，为了方便起见，Dk的单位表述为“Dk单位”，如在使用公式前，对10-11乘上1011：
当使用球状表面探头测量水凝胶镜片：
…………………………(3)
当使用平面探头测量水凝胶镜片：
…………………………(4)
当使用球状表面探头测量非水凝胶镜片：
…………(5)
当使用平面探头测量非水凝胶镜片：
…………(6)
非水凝胶镜片修正公式中包含Dk值，在这个阶段是未知的。为了解决这个难点，按公式(7)用t/Dk值(无界层效应修正)计算Dk，用该方法得到的Dk值足够接近于真实值。
………………(7)
式中：
i∑——n次测量的总和，每次测量都有厚度(ti)和阻率(t/Dk)i。
公式(7)得到的Dk值已经与用于边缘效应修正公式所需的值足够接近。然后Dk按照4.3.3.4计算，最后结果Dk值是经过边缘和界层效应修正的。
4.3.3.4界层效应修正
对每种材料测试，至少采用4个具有代表性的不同厚度来测定初级(测量)Dk/t值，当透氧量倒数t/Dk与厚度t绘制曲线时，最小二乘回归线的斜率就是修正界层效应的透氧系数的倒数(1/Dk)。
该步骤用于减少在极谱方法中常见的实验假象，由于在样品前后表面有停滞的水界层，同样在非水凝胶镜片和氧探头的阴极间放置的“水桥”(湿润滤纸)也会产生阻碍。这个界层对氧流量产生了一个稳定的，较大的阻力。这些膜的阻力加上样品的阻力形成了仪器直接测量的总阻力，通过电流计算的初级Dk/t值，在经过边缘效应修正后仍然受到这些影响。但是，如果仪器是修正模式和按照下面的正确步骤，这些界层效应随厚度变化阻力为0。这样，通过上述的统计倒数斜率技术可消除界层效应在计算初级Dk值的影响。
4.3.3.5测试的重复性
采用极谱法单次测量透氧系数(Dk)修正，每种材料至少4个不同厚度进行测定，重复性偏差应在±10％之内。
4.3.3.6试剂和材料
4.3.3.6.1混合氧气：混合氧气(容积百分比20.9％)和氮气或其他气体(容积百分比79.1％)的气体，若大气符合要求也可使用。应进行增湿处理，与测试样品前表面接触时，应为饱和水蒸气气体。
4.3.3.6.2 滤纸：以非水凝胶材料的后表面与氧探头的前表面间的饱和盐溶液作为“水桥”。测试时滤纸层应采用同样的类型和厚度，应持续饱和。代表性的是卷烟纸，其他滤纸也可使用。
4.3.3.7仪器
在图3和图4中给出了一个透氧仪的示意图，它由一个夹紧装置，O形圈，尼龙网，滤纸，加热箱，热敏电阻，极谱探头，欧姆表和微安表组成。通过夹紧装置把与测试样品前表面接触的尼龙网把测试样品紧压在探头的阴极上，O形圈将尼龙网位固定在适当的位置。当夹紧时，一片水凝胶接触镜测试样品就处于极谱探头与尼龙网之间(见图2和图3)。