The standards issued by the national authorities are complied with the participations of various groups of people from public authorities, the business sector, industry, science and the general public. The national authorities play a major role in the compilation and publication of national and international standards.
National Standard Institutes (such as DIN, ANSI, AFNOR,… ),regional standards committees such as the European Standardisation Committee (CEN) and the International Standardisation Organisation (ISO) are responsible for establishing fundamental technical standards and for stipulating the procedures and terminology used in optometry.
These institutions specify and constantly update the parameters which are essential for quality and uniform international standards.
The European Union
Within the European Union, merchandise must be able to move without obstruction and it must meet basic requirements with regard to its safety, suitability and performance. To achieve this goal, directives are compiled which must be implemented in the national legislation of the individual member states.
The following standards apply for the field of optometry:
DIN 5361 for spectacle frames,
DIN EN ISO 14889 for basic requirements to be met by spectacle lenses,
DIN EN ISO 8980/1-3 for the requirements to be met by special lens types,
DIN EN ISO 13666 for ophthalmic terminology,
and the directives 89/686/EEC for sunglass lenses and 98/42/EEC for medical devices.
The latter contains stipulations which must be met by spectacle lenses, spectacle frames, contact lenses and ophthalmic instruments.
Since June 14, 1998, the CE (CE = Communité Européen) labelling stipulations have been in force for products to which EU directives and the appropriate standards apply.
The CE mark is the consumer’s guarantee that the minimum safety and performance requirements are met by the product to the extent stipulated by standards.
The CE Marking
The CE marking is applied to a clearly visible area of the product by the manufacturer, provided, as is the case with spectacle lenses, it would not impair the function of the product. In such cases, the packaging and instructions for use are labelled accordingly.
The ZEISS guarantee certificate you receive from your optician with your new spectacle lenses, verifies that you have purchased a high-quality product.
It contains, for example, the 6 criteria which are distinct traits of ZEISS quality:
- ZEISS is certified to DIN EN ISO 9001/2008.
- We guarantee that the optical quality of our lenses takes precedence over all other product criteria.
- The internal test specifications of ZEISS exceed the stipulations of the relevant standards.
- ZEISS can also provide you with lenses in very high or unusual prescriptions. And our many different coatings are also available for these powers.
- You can be sure that ZEISS lenses will continue to be available in the long term, ensuring that you also receive optimum lenses with time-tested quality for your eyes in the future.
- We ensure that ZEISS lenses are fitted exclusively by selected opticians.
The best way to clean your lenses is to hold them under running, cold water using pH-neutral cleaning agents. Dirt particles are simply washed off and cannot therefore cause any damage to the surface when the lenses are dried with a clean, soft cloth. For cleaning your lenses when you are out and about, we recommend the micro-fibre cloths and the special ZEISS lens cleaning agent. Other textiles may cause scratches on your lenses.
Important: Please do not expose your lenses to high temperatures of over
80 °C (e. g. in the sauna or on the dashboard of your car in the summer).
These standards, which were compiled with the participation of international experts, stipulates the basic requirements to be met by finished uncut spectacle lenses. These requirements cover such subjects as physiological compatibility, flammability, testing for mechanical strength and the transmittance of uncut finished spectacle lenses.
Transmittance, particularly the requirements to be met by lenses used by drivers, is of great importance not only for ZEISS as a lens manufacturer, but also for the optician.
If, for cosmetic or medical reasons, patients wish to purchase lenses which are not suitable for use in traffic or for night driving, the optician is obliged to inform them accordingly. He or she should stress that it is not only the intensity of the tint that influences the suitability of a lens for use in traffic, but also the ability of a lens to transmit certain wavelengths. For instance, a lens with a certain filter effect may subjectively appear to be "bright" enough for diving in twilight or at night, but it may falsify the colour of a traffic signal to such an extent that it is not suitable for driving.
- Lenses used for driving in the daytime must display a luminous transmittance τν of > 8% in the major reference point using standard illuminant D 65.
- Lenses used for driving in twilight or at night must display a luminous transmittance τν of ≥75% in the major reference point using standard illuminant D 65.
- The spectral transmittance τ (λ) of the lens must not be less than 0.2 times the luminous transmittance τν for any wavelength in the range from 475 to 650 nm.
- The relative visual attenuation quotient Q must not be less than 0.8 for red, yellow and 0.6 for green, and 0.4 for blue.
Needless to say, all lenses supplied by ZEISS are tested and labelled in accordance with the stipulations of these standards (suitability for use in traffic / suitability for twilight or night driving as per DIN EN ISO 8980-3).All ZEISS lenses also meet the minimum requirements concerning mechanical strength, inflammability and physiological compatibility.
- Luminous Transmittance τν
Luminous transmittance τν is the ratio of the luminous flux transmitted by the lens to the incident luminous flux, taking into account the spectral luminous efficiency of the eye in daylight V(λ).
- Spectral Transmittance τ(λ)
The spectral transmittance τ(λ) is the ratio of the spectral radiant flux transmitted by the lens to the incident radiant flux at any specified wavelength λ.
- Standard Illumnant D 65
The standard illuminant D 65 represents medium daylight conditions with the colour temperature 6500 K and is usually generated by the use of xenon lamps with filters.
- Attenuation Quotient Q
The relative visual attenuation quotient Q is the ratio of the luminous transmittance of a tinted lens for the spectral radiant power distribution of the light emitted by a traffic signal tsign to the luminous transmittance of the same lens for the standard illuminant D 65. Q does not therefore provide any information on the wearer’s colour perception with a lens, but only indicates whether the luminance of a traffic light is more or less strongly attenuated than the ambient luminance (Q less or greater than 1).
- Spectral Luminous Efficiency of the Eye in Daylight τ(λ)
The spectral luminous efficiency of the eye in daylight τ(λ) is the defined relative spectral sensitivity of the light-adapted photopic standard eye whose maximum is referred to λ = 555 nm in air.
Apart from DIN EN ISO 14889 and 8980-3, there are other standards which are also essential for ophthalmic opticians and optometrists which go into more detail with regard to the various types of ophthalmic lenses and their mounring:
- DIN EN ISO 8980-1 Requirements for single vision and multifocal lenses
- DIN EN ISO 8980-2 Requirements for progressive lenses
- DIN EN ISO 13666 Ophthalmic terms and definitions
- DIN EN ISO 21987 Ophthalmic optics - Mounred spectacle lenses