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| FDA Groups |
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THe FDA gives each contact lens a generic name. In general, all hydrogel lens generic names end in the suffix "filcon" and all nonhydrogel lenses end in "focon"
Hydrogel lenses are categorized into four groupings for purposes of evaluating effects of accessory products upon the lens material. Lenses with less than 50 percent water content are considered to be "low water" and the others are "high water." Less reactive surfaces are termed "nonionic" and more reactive materials are labeled "ionic."
Disinfection of low water content Group 1 and Group 3 lenses can usually be done safely and effectively by thermal, chemical, or hydrogen peroxide systems. High water content Group 2 and Group 4 lenses should generally not be thermally disinfected, but chemical or hydrogen peroxide systems are usually safe and effective. However, some Group 4 ionic polymers may react negatively with potassium sorbate- or sorbic acid-preserved solutions.
The Dk (permeability) of hydrogel contact lenses is a function of the water content, i.e., lower water content materials have lower Dk values and higher water content lenses have higher Dk values. Dk values are theoretically an absolute for any given material, but practically the values found by different researchers vary somewhat. Each generic material below is accompanied by a representative Dk number.
It is also important to remember that Dk/L (central transmissibility) and Dk/L (average overall transmissibility) are dependent upon lens thickness configuration and are more important than Dk.
Group 1
Low Water (<50% H20)
Nonionic Polymers
Teflicon (38%) (Dk = 8.9)
Tetrafilcon A (43%) (Dk = 9)
Crofilcon (38%) (Dk = 13)
Helfilcon A&B (45%) (Dk = 12)
Mafilcom (33%) (Dk = 4)
Polymacon (38%) (Dk = 9)
Hioxifilcon B (49%) (Dk = 15)
Lotrafilcon A (24%) (Dk = 140)
Group 2
High Water (>50% H20)
Nonionic Polymers
Lidofilcon B (79%) (Dk = 38)
Surfilcon A (74%) (Dk = 35)
Lidofilcon A (70%) (Dk = 31)
Netrafilcon A (65%) (Dk = 34.5)
Hefilcon C (57%)
Alfafilcon A (66%) (Dk = 32)
Omafilcon A (59%) (Dk = 33)
Vasurfilcon A (74%) (Dk = 39.1)
Hioxifilcon A (59%) (Dk = 36)
Nelfilcon A (69%) (Dk = 26)
Hilafilcon A (70%) (Dk = 35)
Hilafilcon B (59%) (Dk = 22)
Group 3
Low Water (<50% H20)
Ionic Polymers
Bufilcon A (45%) (Dk = 16)
Deltafilcon A (43%) (Dk = 10)
Phemfilcon (38%) (Dk = 9)
Group 4
High Water (>50% H20)
Ionic Polymers
Bufilcon A (55%) (Dk = 16)
Perfilcon A (71%) (Dk = 34)
Etafilcon A (58%) (Dk = 28)
Focofilcon A (55%) (Dk = 16)
Ocufilcon B (53%) (Dk = 16)
Ocufilcon C (55%) (Dk = 16)
Ocufilcon D (55%) (Dk = 19.7)
Ocufilcon E (65%) (Dk = 22)
Ocufilcon F (60%) (Dk = 24.3)
Phemfilcon A (55%) (Dk = 16)
Methafilcon A (55%) (Dk = 18)
Methafilcon B (55%) (Dk = 18)
Vilfilcon A (55%) (Dk = 16)
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FDA Group
FDA - (Food and Drug Administration) is a U.S government body that oversees contact lenses, intraocular lenses & eye drops. |
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