Ophthalmic optics—Contact lenses—Part 5: Testing methods for optical properties
1 Scope
GB/T 11417.5 specifies the testing methods of optical properties of contact lenses.
This part is applicable to the finished contact lenses.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 5702-2003 Methods of measuring the color of light sources
GB/T 11417.1-2002 Ophthalmic optics—Contact lenses—Part 1: Vocabulary, classification system and recommendations for labeling specifications
GB/T 11417.4-2002 Ophthalmic optics—Contact lenses—Part 4: Saline solution for contact lens testing
GB 17341-1998 Optics and optical instruments—Focimeters
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 11417.1-2012 and the following apply.
3.1
reproducibility conditions
conditions where independent test results are obtained on the same test sample by different operators using different equipment according to the same method in different laboratories
3.2
reproducibility value
R
absolute difference between the two independent test results obtained under the reproducibility conditions, with the probability that the expectation is not greater than the R value is 95%
4 Measurement of back vertex power
4.1 General
The back vertex power of contact lenses may be measured by focimeter in air, and by Moiré deflectometer method and Hartmann method in saline solution (see 4.2.3 and Annex A).
4.2 Focimeter measuring method
4.2.1 Instrument properties
A focimeter conforming to GB 17341-1998 shall be used for measurement, but will require modification of the contact lens support as specified below.
The increased sagittal depth of contact lenses compared to spectacle lenses, and the limited diameter of the optic zone of contact lenses, will not allow proper positioning of the back vertex and optic zone of a contact lens at the spectacle lens stop usually provided with the focimeter. Therefore, in order to ensure the accurate measurement of the back vertex power of the contact lens, the focimeter shall be modified with a special contact lens support (see Figure 1). The contact lens support shall be designed so that the contact lens rests on the supporting ring only, as shown in Figure 2.
Figure 1 shows an example of a suitable support. Its central aperture has a diameter of 4.50 mm ± 0.50 mm and projects 0.55 mm ± 0.02 mm less than the spectacle lens support which it replaces. The radius rc of the support ring supporting the posterior surface of the contact lens is 0.50 mm. This will provide the appropriate vertex power, by compensating for the sagittal depth change due to a back optic zone radius of 8.00 mm in a contact lens. Lenses with a back optic zone radius value substantially different from this may require further vertex distance correction.
Note: Although the contact lens stop will reduce sagittal errors, it will have little effect on reducing spherical aberration.
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1 Scope
2 Normative references
3 Terms and definitions
4 Measurement of back vertex power
5 Determination of spectral and luminous transmittance
6 Determination of color rendering index for color vision influence analysis
Annex A (Informative) Measurement of back vertex power of contact lenses in saline solution
Annex B (Normative) Determination of color rendering index for color vision influence analysis of contact lenses
