The United States Adopted Name (USAN) Council became involved in polymer nomenclature in 1971 and formulated the first rules for nonproprietary names to contact lens materials in 1972. Based on polymer technology at that time and information from the U.S. Food and Drug Administration, lens polymers were divided into the filcon (hydrophilic) and the focon (hydrophobic) series. These rules update the initial guidelines incorporating many of the guiding principles under the rules for coining pharmaceutical names.
A nonproprietary name for a contact lens material should be useful primarily to practitioners, specifically ophthalmologists, optometrists, opticians, educators and other eye care and eye care device specialists. Please take note of the following general rules:
- For nomenclature purposes, contact lens materials are divided into hydrophilic and hydrophobic groups, depending on their water content. Materials with water content greater than or equal to 10% by weight at ambient temperature are assigned "-filcon" names. The "-focon" stem is assigned to hydrophobic lens materials with water content less than 10%.
- In addition to water content, nomenclature for contact lens materials depends primarily on the polymeric composition, i.e., the repeating monomer units comprising the lens material. These repeating units include linear monomers. However, initiators, catalysts, fillers, chemically or physically bound or entrapped color additives, UV absorbers and other additions are excluded in establishing the polymer composition for nomenclature purposes.
- The first member of a series is assigned a unique nonproprietary name containing the proper -filcon or -focon suffix stem. A separate capital letter "A" is added after each parent designation. Subsequent designations for polymers consisting of identical monomers receive the same parent name but a different appended letter (B, C and D, etc.). These letters are needed to differentiate between polymers of identical monomeric units but with different ratios of units that have different physiochemical properties, as determined by water content, oxygen permeability [Dk] value, specific gravity, refractive index, surface charge, wetting angle, elasticity and toughness of the lens.
- A contact lens material having the same repeating monomers as a named substance but made by a different manufacturing process (e.g., lathe-cut versus cast-molded) will not receive a new USAN if the lens material has the same water content and oxygen permeability as the initially named polymer.
- Because water content and oxygen permeability values affect assignment of a name, experimental error must be included for both to indicate the precision of the measurement. In the USAN Council's opinion, if they do not indicate a statistically significant difference from existing compounds, then the USAN Council may choose not to assign a USAN to the material.
- CAS numbers must be submitted for each monomer as well as the entire polymer. If submitting for a hybrid material consisting of 2 or more polymer components, CAS numbers must be supplied for both components and every monomer.
- Corrections and revisions to formulas and structures are to be submitted electronically in MS Word or Chemdraw files.
- The addition of a surface treatment to an existing lens material that has been assigned a USAN will not result in assignment of a new USAN.
- A new USAN will not be assigned to contact lens material containing either chemically bound or physically entrapped color additives. The USAN Council defers to FDA labeling rules to identify color additives used to make tinted lenses.
- A new USAN will not be assigned to contact lens materials containing either chemically bound or physically entrapped ultraviolet absorbers. The USAN Council defers to the FDA labeling rules to identify UV absorber used to make these lenses.
- A revision of the guiding principles regarding the publication timeframe of USAN for contact lens materials was approved by the USAN Council at their Feb. 10, 2003 meeting. Therefore, information on USAN for contact lens materials will not be published until after the manufacturer files a premarket approval (PMA) application with the FDA Center for Devices and Radiological Health and this notice appears in the database.
- Please note that contact lens materials are not assigned nonproprietary names by the World Health Organization International Nonproprietary Names Expert Group. Names for contact lens materials have USAN status only.
- Deferred negotiations:
a. The USAN Council Secretariat will defer an ongoing negotiation for 6 months, plus 1 additional 3-month extension upon request of the manufacturer. If the USAN Council has selected a name candidate and recommended this name to the manufacturer, the maximum deferral is one 6-month period.
b. The negotiation will be canceled after the maximum 9-month deferral has lapsed.
c. If the negotiation is to be reopened at a later time, it will be treated as a new application and will receive a new USAN file. The manufacturer will be expected to submit a new USAN application form, update the background information and submit the appropriate fee.
- Identical negotiations submitted by 2 or more manufacturers will be conducted in accordance with the Council's practice of maintaining confidentiality. The applicants involved will not be notified of the multiple sources of the submission. However, the name selected by the USAN Council will need to be accepted by each manufacturer involved in the negotiation process.
Guiding Principles for Coining Contact Lens Names
Since the stems of contact lenses are already established—either a "-filcon" or "-focon" stem—it is mainly the prefix that presents a challenge. Please use the following guiding principles when considering a prefix:
- A nonproprietary name for a contact lens material should be useful primarily to health care practitioners and eye care specialists.
a. The primary criterion for judging usefulness is suitability, including safety for use in routine relevant communications throughout the United States.
b. The second criterion is suitability for use in educational programs and in scientific and lay publications.
c. Although contact lenses do not receive an INN, the third criterion is suitability for use internationally and translation into different languages.
- Attributes that contribute to usefulness are simplicity (brevity and ease of pronunciation), euphony and ready recognition and recall.
a. A contact lens prefix should be no more than 3 syllables. The contact lens name thus should have no more than 5 syllables.
- Hybrid lenses only may have more than 1 word in the name. Only hybrid lens names may contain hyphens.
- Because of the international exchange of information, specific guidelines have been formulated to ensure appropriate translation of nonproprietary names into other languages. The following rules of preferred spelling should be used when coining USAN designations for contact lenses:
a. The letter "f" should be used instead of "ph"
b. The letter "t" should be used instead of "th"
c. The letter "e" should be used instead of "ae" or "oe"
d. The letter "i" should be used instead of "y"
e. "ar," "rac," "lev," "dex," or "es" are reserved for stereochemical configurations and should not be used for contact lenses
- Additionally, these letter combinations are restricted until further notice. Please avoid the following prefixes:
a. The beginning letter combination of "me"
b. The beginning letter combination of "str"
c. "z" or "x" as a beginning letter
- A name should reflect characteristics and relationships that will be of practical use to the users. However, this does not allow for prefixes that would proffer an unfair competitive or marketing advantage. For example, names that seek to claim the product is the "greatest," "No. 1," "ecologically-friendly," "environmentally friendly," "nature-friendly" or imply a "professional/expert" endorsement over other products; or names that connote light, sun, illumination, water and other various environmental attributes and properties either in English or in other languages are not allowed and will not be accepted by the USAN Council.
- Numbers cannot be part of the contact lens prefix (digits, spelled-out numbers, numeric prefixes or numbers in other languages are no longer accepted).
- A name should be free from conflict with other nonproprietary names and with established trademarks and should be neither confusing nor misleading.
1. Limit contact lens wear during a flight.
Top of the list is to try and limit wearing your contact lenses during a flight. Disposable contact lenses are predominantly made of water, with some contact lenses comprising up to 69% water content. As you may have experienced, during air travel your skin and eyes tend to dry out due to the dry atmosphere on board a plane. In most air conditioned buildings the relative humidity sits between 40 to 70%, while in an aircraft the average humidity can get as slow as 20%. So your contact lenses will dry out and distort during a flight. Our general recommendation is not to wear your contact lenses on a long haul flight and definitely take them out if you plan to sleep on a long haul flight. If you are catching a short haul flight and you do want to wear your lenses, we highly recommend that you use a rewetting drop such as Bion Tears or Systane Ultra to maintain your lenses in a wet state during the flight.
2. Stock up your supply before you leave.
Although most brands of contact lenses are readily available in most global cities, the dispensing laws may vary. So even though you know your power you will very likely be asked to sit an eye test before an optical retailer will supply your product. So if you know you are about to travel, it is advisable to ensure you have topped up your contact lens supply before you depart. Even if you’ve left it to the last minute, Oz Contacts can generally ship your lenses within 48hrs through Australia Post’s eParcel Express service.
3. Pack some contact lenses in your overnight bag.
If you are taking carry-on baggage, it’s always a good idea to allocate some of your contact lens supply to your carry-on bag. There is nothing worse then finding that when you get to your destination that your contact lenses along with the rest of your luggage have ended up in another destination. You should think of keeping some contact lenses with you at all times as a kind of travel insurance in the event that you’re separated from your full supply.
4. Daily contact lenses free up packing space
Daily contact lenses are probably the most convenient way to wear contact lenses if you are travelling. For safety reasons, in most countries passengers are limited to very small quantities of liquid in their baggage (usually no more than 100ml). This unfortunately also includes contact lens solution. So travelling with daily contact lenses instead of reusable lenses means you won’t have to worry about storing contact lens solution in your baggage, and will give you some additional space that you can substitute for an extra fragrance or hair product for example.
5. Solutions come in all shapes and sizes.
If you find that your contact lens prescription is not available in a daily lens and you need a monthly or fortnightly contact lens that requires a contact lens solution cleaner then packing an Alcon Opti-Free Pure Moist 90ml Contact Lens Solution is a great option.
6. Brand Names are worthwhile
Home-brand contact lenses may not be readily available at your destination. Mass optical retailers are beginning to sell more house-brand contact lenses to try and tie in their customers’ loyalty to their practice. If you have been prescribed a home-brand contact lens you may want to find out what the branded equivalent is before you travel just in case your optical retailers home brand is not available at your destination. You can view a comprehensive list of all the branded equivalents here. It’s always good to ask the optometrist to record the branded equivalent on your prescription as well just in case you have to present a contact lens prescription to an optometrist at your travel destination. To save confusion, we always recommend buying the branded version of the product.
7. Keep them clean
You may be in a foreign place, but it’s no excuse to let foreign matter build up on your hands. While travelling in highly trafficked public spaces, there is a greater potential to pick up bacteria or other foreign matter on your fingertips and hands. As we mentioned earlier, being exposed to air-conditioned environments can dry out your lenses. This dryness can create the temptation to readjust your lenses mid-wear, which can cause whatever microscopic matter that was on your hands to be transferred to your eyes. To maintain the sterility of your eye environment, it’s a good idea when travelling to always keep some hand sanitiser and tissues on hand to ensure that before you touch your lenses your fingers are as clean as possible. To help reduce unnecessary finger contact with your eyes, it can also be helpful to carry a compact mirror to help target your contact lens insertion, extraction and adjustment with more precision and hygiene.
8. Give your eyes a vacation, too.
While you’re travelling, you might also consider giving your eyes a vacation as well. Competing with different time zones and surroundings, many travellers get sub-optimal quantity and quality of sleep, which can affect the comfort and health of your eyes. Getting a good 8-10 hours sleep, taking a day off wearing contact lenses, and keeping your body hydrated, can make a major difference to your contact lens experience while you’re away from home.