Article Date: 7/1/2013

Soft Contact Lenses

Soft Contact Lenses

Hydrogel and Silicone Hydrogel Lens General Considerations

The FDA gives each contact lens material a generic name. In general, all hydrogel and silicone hydrogel lens generic names end in the suffix “filcon” and all nonhydrogel lenses end in “focon.”

Hydrogel lenses are categorized into five 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.” Silicone hydrogel lenses are Group 5, which is in the process of being updated and subdivided further. This is described in the article “Proposed Silicone Hydrogel Lens Grouping Systems for Lens Care Product Compatibility Testing” by Joseph Hutter, PhD, Angela Green, PhD, and Malvina Eydelman, MD, in Eye and Contact Lens, 2012 Nov;38(6):358-362. The FDA proposal has been sent out for comments, and it will then be finalized.

Disinfection of hydrogel and silicone hydrogel lenses can usually be done safely and effectively by approved chemical or hydrogen peroxide systems. However, some Group 4 ionic polymers may react negatively with potassium sorbate- or sorbic acid-preserved solutions.

In the term Dk, D stands for diffusion and k for solubility. The oxygen permeability of hydrogel lenses is almost entirely the result of solubility and for GP materials almost entirely the result of diffusion. In silicone hydrogel materials, oxygen permeability is a combination of solubility and diffusion, with the larger amount from diffusion. That is, the hydrogel component in the formulation provides solubility and the silicone component provides diffusion. Each generic material below is accompanied by a representative Dk number.

A clinically useful approximation is to consider Dk values for hydrogel lenses in three groups:

H2ODk
38±%
55±%
75±%

18±
36±

It is also important to remember that Dk/t (central transmissibility) and Dk/t (average overall transmissibility) are dependent upon contact lens thickness configuration and are more important than Dk with hydrogel lenses. With silicone hydrogel contact lenses, Dk/t and Dk/t are more similar than with hydrogel lenses.

This table should assist you in identifying specific lenses in each category as related to disinfection and Dk; and it will also help you determine an appropriate mix of lens types for your practice.

GROUP 1

Low Water (<50% H2O) Nonionic Hydrogel Polymers

tefilcon (38%) (Dk = 8.9)
• LL Bifocal

tetrafilcon A (43%) (Dk = 9)
• Preference
• Preference Toric XR
• Preference Toric

helfilcon A&B (45%) (Dk = 12)
• Continental Toric
• Flexlens
• Flexlens Toric
• Flexlens Aphakic
• Optima Toric

mafilcon (33%) (Dk = 4)
• Menicon

polymacon (38%) (Dk = 9)
• Alden Classic 38 Sphere Toric
• Biomedics 38
• Esstech PS Multifocal
• Esstech PSD
• Esstech SV
• HD
• HD-T
• HDX
• HDX-T
• Horizon 38
• Ideal Soft
• LifeStyle MV2
• LifeStyle Xtra
• LifeStyle 4Vue
• LifeStyle Toric Bifocal
• LL-38
• Metrosoft II
• Metrosoft Toric
• Natural Touch
• Occasions
• Optima 38
• Simulvue 38
• Sof-form II
• Soflens
• Soflens 38
• Soflens Multifocal
• Unilens 38
• Westhin Toric

hioxifilcon B (49%) (Dk = 15)
• Alden HP
• Alden HP Toric
• Aquaease
• Essential Soft Toric Multifocal
• Flexlens
• Quattro
• Satureyes
• Satureyes Toric and Multifocal

Note: All X-Cel lenses are available in helfilcon A, hioxifilcon A, hioxifilcon B, and methafilcon A.

GROUP 2

High Water (>50% H2O) Nonionic Hydrogel Polymers

alfafilcon A (66%) (Dk = 32)
• Soflens Toric

omafilcon A (59%) (Dk = 33)
• Biomedics XC
• Proclear 1-Day
• Proclear EP
• Proclear Multifocal
• Proclear Multifocal Toric
• Proclear Sphere
• Proclear Toric

hioxifilcon A (59%) (Dk = 28)
• Alden HP 59 Sphere
• Extreme H2O 59% Thin
• Extreme H2O 59% Extra

hioxifilcon B (49%) (Dk = 16 )
• Intelliwave Aspheric
• Intelliwave Aspheric Toric
• Intelliwave Multifocal
• Intelliwave Multifocal Toric

hioxifilcon D (54%) (Dk = 21)
• Alden HP 54 Sphere and Toric
• Astera Multifocal
• Astera Multifocal Toric
• Clarity H2O
• C-Vue Advanced Custom Toric
• Extreme H2O 54%
• Extreme H2O 54% Toric

nelfilcon A (69%) (Dk = 26)
• Dailies AquaComfort Plus
• Focus Dailies
• Focus Dailies Toric
• Focus Dailies Progressive
• Novakone, Novakone Toric
• FreshLook One-Day
• Synergy
• Triton

nesofilcon A (78%) (Dk = 42)
• Biotrue Oneday

hilafilcon B (59%) (Dk = 22)
• SofLens Daily Disposable

acofilcon A (58%) Dk = (25.5)
• Flexlens Tricurve Keratoconus

GROUP 3

Low Water (<50% H2O) Ionic Hydrogel Polymers

deltafilcon A (43%) (Dk = 10)
• Metrosoft

GROUP 4

High Water (>50% H2O) Ionic Hydrogel Polymers

etafilcon A (58%) (Dk = 28)
• Acuvue
• 1-Day Acuvue
• 1-Day Acuvue Moist
• Acuvue 2
• Acuvue 2 Colours
• Acuvue Bifocal

focofilcon A (55%) (Dk = 16)
• Fre-Flex

ocufilcon A (46%) (Dk = 15)
• UCL Tresoft
• UCL PR-46

ocufilcon B (53%) (Dk = 16)
• ClearSight 1 Day
• Continental
• Ocu-Flex 53

ocufilcon C (55%) (Dk = 16)
• UCL55
• UCL-Pediatric

ocufilcon D (55%) (Dk = 19.7)
• Biomedics 55
• Biomedics 55 Premier
• Biomedics Toric
• ClearSight 1 Day Toric

ocufilcon E (65%) (Dk = 22)
• Ocuflex 65

phemfilcon A (55%) (Dk = 16)
• Freshlook
• Freshlook Toric
• Freshlook Colorblends Colors Dimensions

methafilcon A (55%) (Dk = 18)
• Alden Classic 55 Sphere
• Alden Classic 55 Toric
• Biocurve Advanced Aspheric
• Biocurve 1-Day
• Biocurve Toric & Sphere
• C-Vue 1 Day ASV
• C-Vue 55
• Elite AC
• Elite Daily
• Elite AC Toric
• Flexlens
• Frequency 55 Sphere & Multifocal
• HD2
• HDX2
• Horizon 55 Bi-Con
• iSight Sphere, Toric, Multifocal
• Kontur
• LL 55
• New Horizons
• Safigel 1 Day
• Sauflon 55 UV
• Sauflon 55 Asphere
• Sof-form 55
• Vertex Sphere
• Vertex Toric

methafilcon B (55%) (Dk = 18)
• Frequency 55 Toric
• Hydrasoft Sphere
• Hydrasoft Toric

vilfilcon A (55%) (Dk = 16)
• Focus Monthly Softcolors
• Soft 55
• Soft 55 EW

GROUP 5

Silicone Hydrogel Polymers

lotrafilcon A (24%) (Dk = 140)
• Air Optix Night & Day Aqua

lotrafilcon B (33%) (Dk = 110)
• O2Optix
• Air Optix for Astigmatism
• Air Optix Aqua Multifocal
• Air Optix Aqua

galyfilcon A (47%) (Dk = 60)
• Acuvue Advance
• Acuvue Advance for Astigmatism
• Acuvue Advance Plus

narafilcon A (46%) (Dk = 100)
• 1-Day Acuvue TruEye

narafilcon B (48%) (Dk = 55)
• 1-Day Acuvue TruEye

senofilcon A (38%) (Dk = 103)
• Acuvue Oasys
• Acuvue Oasys for Astigmatism
• Acuvue Oasys for Presbyopia

comfilcon A (48%) (Dk = 128)
• Biofinity
• Biofinity Multifocal
• Biofinity Toric

enfilcon A (46%) (Dk = 100)
• Avaira
• Avaira Toric

balafilcon A (36%) (Dk = 112)
• C-Vue Hydravue Multifocal
• PureVision
• PureVision Multi-Focal
• PureVision Toric
• PureVision 2
• PureVision 2 for Astigmatism

efrofilcon A (74%) (Dk = 60)
• C-Vue Hydravue
• C-Vue Hydravue Custom Toric
• C-Vue Hydravue Multifocal
• C-Vue Hydravue Toric Multifocal
• Intelliwave Aspheric
• Intelliwave Aspheric Toric
• Intelliwave Multifocal
• Intelliwave Multifocal Toric
• KeraSoft IC

delefilcon A (33% core, ≥80% surface) (Dk = 140)
• Dailies Total1

Spherical Clear and Visibility Tint Disposable and/or Planned Replacement Hydrogels

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Disposable and/or Planned Replacement Tinted Enhancer and Opaque Hydrogels

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Toric Disposable and/or Planned Replacement Hydrogels

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Multifocal Disposable and/or Planned Replacement Hydrogels

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Daily Wear Spherical Clear and Visibility Tint Hydrogels

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Extended Wear Spherical Clear and Visibility Tint Hydrogels

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Therapeutic Spherical Clear and Visibility Tint Hydrogels

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Aphakic Spherical Clear and Visibility Tint Hydrogels

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Special Design Spherical Clear and Visibility Tint Hydrogels

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Daily Wear Tinted Enhancer and Opaque Hydrogels

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Customized Tinting

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Extended Wear Tinted Enhancer and Opaque Hydrogels

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Daily Wear Toric Hydrogels

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Extended Wear Toric Hydrogels

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Daily Wear Multifocal Hydrogels

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Extended Wear Multifocal Hydrogels

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Multifocal Toric Hydrogels

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Hybrid Soft Skirt/GP Center

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Contact Lens Spectrum, Issue: July 2013, page(s): 5 - 21