ISO 11539 pdf download.Ophthalmic optics — Contact lenses — Classification of contact lenses and contact lens materials
1 Scope
This International Standard describes a method for classifying contact lenses and the materials used for their manufacture. It permits the specific and non-proprietary identification, in simplified form, of the major chemical components of the material.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 8320-1 , Contact lenses and contact lens care products — Vocabulary — Part 1 : Contact lenses. ISO 991 3-1 , Optics and optical instruments — Contact lenses — Part 1 : Determination of oxygen permeability and transmissibility with the FATT method. ISO 991 3-2, Optics and optical instruments — Contact lenses — Part 2: Determination of oxygen permeability and transmissibility by the coulometric method. ISO 1 0339, Ophthalmic optics — Contact lenses — Determination of water content of hydrogel lenses.
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 8320-1 apply.
4 Method of classification
4.1 General The specific classification of a contact lens or contact lens material is given as a six-part code as follows: (prefix) (stem) (series suffix) (group suffix) (Dk range) (modification code) For hydrogel contact lens materials, the classification denotes whether the material is ionic and the range in which the water content of the material lies. For non-hydrogel contact lens materials, the classification indicates the presence/absence of silicon/fluorine and the oxygen permeability grouping. For both types of material, the presence or absence of surface modifications is noted (see 4.7).4.2 Prefix The prefix is a term assigned to a material to designate a specific chemical formulation. Use of this prefix, which is administered by the United States Adopted Names (USAN) Council 1 ) , is optional for all countries other than the United States of America. 4.3 Stem Two types of stem are used. The filcon stem is affixed to the prefix and is applied for materials which contain у1 0 % water by mass (hydrogel materials). The focon stem is affixed to the prefix and is applied for materials which contain Ͻ1 0 % water by mass (non-hydrogel materials). 4.4 Series suffix The series suffix is also administered by the USAN Council, and is used in cases in which the original ratio of monomers of an existing contact lens polymeric material is changed to make a new contact lens polymeric material. In this case, the capital letter “A” is added after the stem designation. Subsequent changes in monomer ratio are designated by the next letter of the alphabet. These letters are used to differentiate copolymers of unchanged monomer units but with different ratios. The series suffix may be omitted in cases where there is only one unique monomer ratio.
4.5 Group suffix 4.5.1 For hydrogel (filcon) materials, the group suffix, represented by a Roman numeral, indicates the range of water content in accordance with ISO 1 0339 and the ionic content: I low water content, non-ionic: Materials which contain less than 50 % water and which contain 1 % or less (expressed as mole fraction) of monomers that are ionic at pH 7,2. II medium and high water content, non-ionic: Materials which contain 50 % water or more, and which contain 1 % or less (expressed as mole fraction) monomers which are ionic at pH 7,2. III low water content, ionic: Materials which contain less than 50 % water and which contain greater than 1 % (expressed as mole fraction) monomers which are ionic at pH 7,2. IV medium and high water content, ionic: Materials which contain 50 % water or more, and which contain greater than 1 % (expressed as mole fraction) monomers which are ionic at pH 7,2. NOTE Low water content is defined as less than 50 % water; medium water content as from 50 % to 65 % water, inclusive; and high water content as greater than 65 % water. Hence, group suffixes II and IV include all materials having water contents of 50 % or greater. 4.5.2 For non-hydrogel (focon) materials, the group suffix, represented by a Roman numeral, indicates the presence or absence of silicon and/or fluorine: I Materials which do not contain either silicon or fluorine II Materials which contain silicon but not fluorine III Materials which contain both silicon and fluorine IV Materials which contain fluorine but not silicon NOTE Polymer formulations may also contain initiators, catalysts, fillers and wetting agents which may be present in the final material.