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 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.” Silicone hydrogel lenses are low water.
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:
HO |
DK |
38±% |
9± |
55±% |
18± |
75±% |
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) |
• Illusions |
• STD |
• Softint |
• LL Bifocal |
tetrafilcon A (43%) (Dk = 9) |
• Cooper Clear |
• Preference |
• Cooper Toric |
• Preference Toric |
helfilcon A&B (45%) (Dk = 12) |
• Continental Toric |
• Flexlens Aphakic |
• Flexlens |
• Optima Toric |
• Flexlens Toric |
|
mafilcon (33%) (Dk = 4) |
• Menicon |
|
polymacon (38%) (Dk = 9) |
• Allvue |
• LL38 |
• Biomedics 38 |
• Metrosoft II Multifocal |
• CustomEyes 38 |
|
• EpconSOFT |
• Metrosoft Toric |
• Esstech PS |
• Natural Touch |
• Esstech PSD |
• Occasions |
• Esstech SV |
• Optima 38 |
• HD |
• PS-45 Multifocal |
• HD-T |
• Simulvue 38 |
• HDX |
• Sof-form II |
• HDX-T |
• Soflens |
• Horizon 38 |
• Soflens 38 |
• LifeStyle MV2 |
• Soflens Multifocal |
• Ideal Soft |
• Softics |
• LifeStyle Xtra |
• SoftView |
• LifeStyle 4Vue |
• Unilens 38 |
• LifeStyle Toric Bifocal |
• Westhin Toric |
|
|
hioxifilcon B (49%) (Dk = 15) |
• Alden HP |
• Flexlens |
• Alden HP Toric |
• Quattro |
• Aquaease |
• Satureyes |
• Essential Soft Toric Multifocal |
• Satureyes Toric and Multifocal |
|
|
Note: All X-Cel lenses are available in helfilcon A, hioxifilcon A, hioxifilcon B, and methafilcon A. |
|
|
Silicone Hydrogel Polymers
|
lotrafilcon A (24%) (Dk = 140)
|
• Air Optix Night & Day Aqua |
|
|
lotrafilcon B (33%) (Dk = 110)
|
• O2Optix
• Air Optix Aqua
• 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 B (48%) (Dk = 55) |
• 1-Day Acuvue TruEye
|
senofilcon A (38%) (Dk = 103) |
• Acuvue Oasys
• Acuvue Oasys for Astigmatism
• Acuvue Oasys for Presbyopia
|
sifilcon A (32%) (Dk = 82)
|
• O2Optix Custom
|
comfilcon A (48%) (Dk = 128)
|
• Biofinity
• Biofinity Toric
|
enfilcon A (46%) (Dk = 100)
|
• Avaira
• Avaira Toric
|
efrofilcon A (74%) (Dk = 60) |
• C-Vue Hydravue
• C-Vue Hydravue Custom Toric
• C-Vue Hydravue Multifocal
• C-Vue Hydravue Toric Multifocal
|
GROUP 2 |
High Water (>50% H2O) Nonionic Hydrogel Polymers
|
lidofilcon A (70%) (Dk = 31)
|
• ActiFresh 400
• CV 70
|
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
|
vasurfilcon A (74%) (Dk = 39.1) |
• Precision UV
|
hioxifilcon A (59%) (Dk = 28) |
• Alden HP 59 Sphere
• Extreme H2O 59% Thin
• Extreme H2O 59% Extra
|
hioxifilcon D (54%) (Dk = 21)
|
• Clarity H2O
• C-Vue Advanced Custom Toric
• Extreme H2O 54%
• Extreme H2O 54% Toric
|
nelfilcon A (69%) (Dk = 26)
|
• Dailies AquaComfort Plus
• Focus Dailies
• Synergy
• Focus Dailies Toric
• Triton
• Focus Dailies Progressive
• FreshLook One-Day
|
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
|
bufilcon A (45%) (Dk = 16)
|
• Hydrocurve II 45
• Soft Mate B
|
deltafilcon A (43%) (Dk = 10)
|
• Amsoft
• Amsoft Thin
• Comfort Flex
• Custom Flex
• Metrosoft
• Soft Form Toric
|
phemfilcon A (38%) (Dk = 9) |
• DuraSoft 2
• DuraSoft 2 Optifit
|
Silicone Hydrogel Polymers
|
balafilcon A (36%) (Dk = 112) |
• PureVision
• PureVision Multi-Focal
• PureVision Toric
|
GROUP 4 |
High Water (>50% H2O) Ionic Hydrogel Polymers
|
perfilcon (71%) (Dk = 34) |
• Permalens
• Permalens XL
• Permalens Therapeutic
• Permalens Aphakic
|
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 B (53%) (Dk = 16) |
• ClearSight 1 Day |
• Continental |
• Ocu-Flex 53
|
ocufilcon C (55%) (Dk = 16) |
• UCL 55 |
• UCL-Pediatric
|
ocufilcon D (55%) (Dk = 19.7) |
• Biomedics 55
• ClearSight 1 Day Toric |
• Biomedics 55 Premier |
• Biomedics Toric
|
ocufilcon E (65%) (Dk = 22) |
• Ocuflex 65
|
ocufilcon F (60%) (Dk = 24.3) |
• Hydrogenics 60 UV
|
phemfilcon A (55%) (Dk = 16) |
• DuraSoft 3 |
• Freshlook |
• DuraSoft 3 Optifit |
• Colorblends |
• Freshlook |
• Wildeyes |
• Freshlook Toric
|
methafilcon A (55%) (Dk = 18) |
• Alden Classics |
• Alden Classics Toric |
• Biocurve Advanced Aspheric |
• Biocurve 1-Day |
• Biocurve Toric & Sphere |
• C-Vue 1 Day ASV |
• C-Vue 55 |
• Edge III 55 |
• Elite AC |
• Elite Daily |
• Elite AC Toric |
• Flexlens |
• Frequency 55 Sphere & Multifocal |
• HD2 |
• HDX2 |
• Horizon 55 Bi-Con |
• 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 1-2 Week Softcolors |
• Focus Monthly Softcolors |
• Soft 55 |
• Soft 55 EW |
Contact Lens Spectrum, Issue: July 2011