Soft contact lenses are one of several types of contact lenses for corrective vision eyewear as prescribed by optometrists and ophthalmologists.[1]

Background

In the US market, soft contact lenses are approved by the US Food and Drug Administration.[2] The American Optometric Association published a contact lens comparison chart called Advantages and Disadvantages of Various Types of Contact Lenses on the differences between them.[3] These include:

  • soft contact lenses
  • rigid gas-permeable (RGP)
  • daily wear
  • extended wear
  • disposable
  • planned replacement contact lenses.

The US Food and Drug Administration (FDA) defines soft contact lenses as:

made of soft, flexible plastics that allow oxygen to pass through to the cornea. Soft contact lenses may be easier to adjust to and are more comfortable than rigid gas permeable lenses. Newer soft lens materials include silicone-hydrogels to provide more oxygen to your eye while you wear your lenses.[4]

History

The first contact lenses were made of glass, in 1888. Initially the glass was blown but soon lenses were made by being ground to shape. For the first fifty years, glass was the only material used. The lenses were thin, yet reports of injury were rare. In 1938 perspex (polymethylmethacrylate, or PMMA) began to replace glass in contact lens manufacture. PMMA lenses were easier to produce so the production of glass lenses soon ended. Lenses made of PMMA are called hard lenses.[5] Soft contact lenses were first produced in 1961 by Czech chemical engineer Otto Wichterle using polyhydroxyethylmethacrylate (pHEMA), a material that achieved long-term commercial application. Lenses made of polyacrylamide were introduced in 1971.[5]

Types

The FDA classifies soft contact lenses into four groups for the US market. They are also subcategorized into 1st generation, 2nd generation, and 3rd generation lens materials.[6] These 'water-loving' soft contact lens materials are categorized as "Conventional Hydrophilic Material Groups ("-filcon"):

GroupWater ContentPercentageIonic/Non-Ionic
ILow Water Content(<50%)Nonionic
IIHigh Water Content(>50%)Nonionic
IIILow Water Content(<50%)Ionic
IVHigh Water Content(>50%)Ionic

Note: Being ionic in pH = 6.0 - 8.0".[7]

The FDA has been considering updating soft contact lens group types and related guidance literature.[8][9][10]

Contact lens polymers

The materials that are classified in the 5 FDA groups include the ones listed in the next 5 sections:[11][12]

FDA classification of soft contact lens materials[13]
FDA lens group Adopted name Transmissibility level

(Dk x10-11)

Water content Chemical composition
I
non-ionic
low water content
galyfilcon A 60 47%
lotrafilcon A 140 24% DMA, siloxane, TRIS
lotrafilcon B 110 33%
polymacon 7.5 36% HEMA
tetrafilcon 9.0 43.5% HEMA, MMA, NVP
II
non-ionic
high water content
alphafilcon A 22.9 66% HEMA, NVP
hilafilcon A 26.9 70%
omafilcon A 19.6 62% HEMA, PC
III
ionic
low water content
balafilcon A 99 36% NCVE, NVP, PBVC, TPVC
bufilcon A 16.0 45% DA, HEMA, MAA
IV
ionic
high water content
etafilcon A 17.0 58% HEMA, MAA
ocufilcon D 19.7 55%
vifilcon A 16.0 55% HEMA, MAA, PVP
DA – diacetone acrylamide; DMA N,N-dimethylacrylamide; HEMA – 2-Hydroxyethyl methacrylate; MAA methacrylic acid; MMA methyl methacrylate; NCVE N-carboxl vinyl ester; NVP N-vinyl pyrrolidone; PBVC – poly[dimethylsiloxyl] di[silybutanol] bis[vinyl carbamate]; PC phosphorylcholine; TPVC – tris-(trimethylsiloxysilyl) propylvinyl carbamate; TRIS – tris-(hydroxylmethyl) aminomethane


Hydrogel groups

Below is a list of most contact lens materials on the market, their water percentage, their oxygen permeability rating, and manufacturer brands.[14][15][16][17] Note that the higher the oxygen transmissibility rating, the more oxygen gets to the eye.

Low water nonionic

Material % WaterOxygen Transmissibility (Dk/t)Brands
Tefilcon388.9Cibasoft, Illusions, Torisoft, Softint, STD, LL Bifocal
Tetrafilcon A439Cooper Clear, Cooper Toric, Preference, Preference Toric, Vantage, Vantage Accents, Vantage Thin, Vantage Thin Accents
Crofilcon3813CSI, CSI Toric
Helfilcon A/B4512Continental Toric, Flexlens, Flexlens Toric, Flexlens Aphakic, Optima Toric, All X-Cel lenses
Mafilcon334Menicon
Polymacon38.68.5-24.3Allvue, Biomedics 38, Clearview, CustomEyes 38, EpconSOFT, EsstechPS, Esstech PSD, Esstech SV, Frequency 38, HD, HD-T, HDX, HDX-T, Horizon 38, Hydron Mini, Hydron Zero 4 SofBlue, Hydron Zero 6 SofBlue, Hydron Versa Scribe, Lifestyle MV2, Ideal Soft, Lifestyle Xtra, Lifestyle 4Vue, Lifestyle Toric Bifocal, LL38, Metrosoft ll Multifocal, Metrosoft Toric, Natural Touch, Occasions, Optima 38/SP, PS-45 Multifocal, Simulvue 38, Sof-form II, SofLens, SofLens38, SofLens Multi-Focal, Softics, SoftView, Unilens 38, Westhin Toric, EZvue Soft Contact Lens, Solotica
Hioxifilcon B4915Alden HP Sphere, Alden HP Toric, Aquaease, Essential Soft Toric Multifocal, Flexlens, Quattro, Satureyes, Satureyes Toric and Multifocal, All X-Cel Lenses

High water nonionic

Material % WaterOxygen Transmissibility (Dk/t)Brands
Surfilcon A7435
Lidofilcon A7031ActiFresh 400, CV 70
Lidofilcon B7938
Netrafilcon A6534.5
Hefilcon B4510Optima Toric
Alphafilcon A6632SofLens Toric for Astigmatism
Omafilcon A58-6028–36.7Proclear 1-Day, Proclear EP, Proclear 1 day Multifocal, Proclear Multifocal Toric, Biomedics XC, Aveo
Omafilcon B6221.3-52.3Proclear Sphere, Proclear toric, Proclear toric XR, Proclear multifocal, Proclear multifocal XR, Proclear multifocal toric
Vasurfilcon A7439.1Precision UV
Hioxifilcon A5928Alden HP Sphere, Alden HP Toric, ExtremeH₂O 59% Thin/Extra, Biocurve Gold Sphere and Toric, Aura ADM, Scout by Warby Parker,[18] Hydro by Hubble, Miru 1 Day[19]
Hioxifilcon D5421Alden HP Sphere, Alden HP Toric, ExtremeH₂O 54%, Clarity H₂0, C-Vue Advanced Custom Toric
Nelfilcon A6926Focus Dailies, Focus Dailies Toric/Progressive, Dailies AquaComfort Plus, FreshLook One-Day, Synergy, Triton
Hilafilcon A7035
Hilafilcon B5922SofLens 59, SofLens Daily Disposable, SofLens Daily Disposables for Astigmatism
Acofilcon A5825.5Flexlens Tricurve Keratoconus
Nesofilcon A7842Biotrue ONEday

Low Water ionic

Material % WaterOxygen Transmissibility (Dk/t)Brands
Bufilcon A4516Hydrocurve II 45, Soft Mate B
Deltafilcon A4310Amsoft, Amsoft Thin, Comfort Flex, Custom Flex, Metrosoft, Soft Form Toric
Phemfilcon389Durasoft 2

High Water ionic

Material % WaterOxygen Transmissibility (Dk/t)Brands
Bufilcon A5516Hydrocurve I, Hydrocurve 3 Toric, Softmate II
Perfilcon A7134Permalens
Etafilcon A5823.8-28Acuvue, Acuvue Bifocal, Acuvue 2, Acuvue 2 Colors, 1-Day Acuvue, 1-Day Acuvue Moist, 1-Day Acuvue Moist for Astigmatism, 1-Day Acuvue Moist Multifocal, 1-Day Acuvue Define, Colornova, Discon, Waldo, Natural Vue, Ocylens
Focofilcon A5516Fre-Flex
Ocufilcon B52-5316-24ClearSight 1-Day, Continental, Ocu-Flex 53
Ocufilcon C5516UCL55, UCL-Pediatric
Ocufilcon D5517.8-28.1Biomedics 55 Premier asphere, Biomedics Toric, ClearSight 1-Day Toric, Horien 1-Day Disposable
Ocufilcon E6522Ocuflex 65
Ocufilcon F6024.3Hydrogenics 60 UV
Phemfilcon A5516Durasoft 3, Freshlook, Wildeyes
Methafilcon A5517.9-37.6Biocurve 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, Expressions Colors, Flexlens, Frequency 55 Sphere/Multifocal, HD2, HDX2, Horizon 55 Bi-Con, Hubble, Kontur, LL55, New Horizons, Revolution, Sauflon 55, Sof-form 55, Sunsoft Eclipse, Sunsoft Toric, Vertex Sphere, Vertex Toric
Methafilcon B5514.5-31.3Frequency 55 Toric, Hydrasoft Sphere, Hydrasoft Sphere Thin, Hydrasoft Aphakic, Hydrasoft Aphakic Thin, Hydrasoft Toric, Hydrasoft Toric Thin
Vilfilcon A5516Focus 1-2 Week Softcolors, Focus Monthly Softcolors, Focus Toric, Focus Progressives, Soft 55, Soft 55 EW

Silicone hydrogel polymers

MaterialFDA Group % WaterOxygen Transmissibility (Dk/t)Modulus (MPa)Center Thickness (mm)Brands
Lotrafilcon A124175[20]1.50.08Air Optix Night & Day Aqua
Lotrafilcon B133110-1381.00.08O2Optix, Air Optix for Astigmatism, Air Optix Aqua, Air Optix Aqua Multifocal
Galyfilcon A14786[21]0.430.07Acuvue Advance with Hydraclear, Acuvue Advance for Astigmatism
Senofilcon A138103-1470.70.07Acuvue Oasys, Acuvue Oasys for Astigmatism, Acuvue Oasys for Presbyopia, Acuvue Oasys 1-Day, Acuvue Oasys 1-Day for Astigmatism, Acuvue Oasys with Transitions, Acuvue Oasys Max 1-Day, Acuvue Oasys Max 1-Day Multifocal
Senofilcon C41129-1470.770.07Acuvue Vita, Acuvue Vita for Astigmatism
Sifilcon A132820.08O2Optix Custom
Comfilcon A148116-1600.750.08Biofinity, Biofinity toric, Biofinity XR, Biofinity XR toric, Biofinity Energys, Biofinity multifocal
Enfilcon A1461000.60.06Avaira, Avaira Toric
Balafilcon A33691-1301.10.09PureVision, PureVision Toric, PureVision Multi-Focal, PureVision2, PureVision2 for Astigmatism, PureVision2 Multi-Focal for Presbyopia
Delefilcon A33-99
(water gradient)
156[22]0.70.09Dailies Total1, Dailies Total1 Multifocal, DailiesTotal1 for Astigmatism
Narafilcon B148551-Day Acuvue TruEye (old)
Narafilcon A461180.660.0851-Day Acuvue TruEye (new)
Stenfilcon A5480-1000.40.08MyDay, MyDay toric, MyDay Multifocal
Somofilcon A5657-860.50.07Clariti 1 day, Clariti 1 day toric, Clariti 1 day multifocal
Fanfilcon A5590-1100.60.06Avaira Vitality, Avaira Vitality toric, 24H Toric
Samfilcon A46[23]163[24]0.70.07Bausch & Lomb Ultra, Bausch & Lomb Ultra for Astigmatism, Bausch & Lomb Ultra for Presbyopia
Elastofilcon0.2340SilSoft Aphakic, SilSoft Super Plus
Kalifilcon A 55 134[25] 0.50.08Bausch & Lomb INFUSE
Asmofilcon A 40 161[26] 0.90.08Miru 1month
Verofilcon A 51-80
(water gradient)
100 0.60.09Alcon Precision1, Alcon Precision1 for Astigmatism
Lehfilcon A 55-99
(water gradient)
154[27] 0.60.08Total30

Production generations

There are three generations of silicone hydrogel contact lens materials:[28]

1st Generation2nd Generation3rd Generation
Material:Lotrafilcon A, Balafilcon ASenofilcon A, Galyfilcon ASamfilcon A, Comfilcon A, Enfilcon A, Asmofilcon A[29]
Features:TRIS structures, plasma treated, high modulusModified Tanaka monomer, lack of coatings, higher Dk for water contentNo TRIS structure, no surface treatments or wetting agents, breaks traditional water-Dk-modulus relationships

References

  1. "About Contact Lenses - clma.net". clma.net. Contact Lens Manufacturers Association. Retrieved 18 June 2016.
  2. Denise Hampton, Ph.D (13 May 2014). "Contact Lens Safety - Ophthalmic Devices Panel" (PDF). www.fda.gov. FDA Division of Ophthalmic and Ear, Nose and Throat Devices. p. 97. Archived from the original (Microsoft PowerPoint) on 18 June 2016.
  3. "Caring for Your Vision: Advantages and Disadvantages of Various Types of Contact Lenses". www.aoa.org. American Optometric Association. Retrieved 18 June 2016.
  4. Center for Devices and Radiological Health. "Contact Lenses - Types of Contact Lenses". www.fda.gov. U.S. Food and Drug Administration. Retrieved 18 June 2016. Public Domain This article incorporates text from this source, which is in the public domain.
  5. 1 2 "Polymers in everyday things – Contact Lenses" (PDF). rsc.org. Royal Society of Chemistry. Archived from the original (PDF) on 19 June 2016. Retrieved 19 June 2016.
  6. "The FDA has created the 4 Lens groups of hydrogels Materials to clarify categories of similar polymers for investigating solutions approvals". Archived from the original on 2016-08-10. Retrieved 2016-06-28.
  7. Ophthalmic Devices Panel of the Medical Devices Advisory Committee (May 13, 2014). "FDA Executive Summary Prepared for the May 13, 2014 Meeting of the Ophthalmic Devices Panel of the Medical Devices Advisory Committee" (PDF). U.S. Food and Drug Administration. p. 2. Archived from the original (PDF) on 7 August 2015. Retrieved 18 June 2016.
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  11. "Contact Lenses: Manufacturing/Chemistry" (PDF). www.fda.gov. U.S. Food and Drug Administration. n.d. p. 25. Archived from the original (PDF) on 1 May 2015. Retrieved 18 June 2016.
  12. "Editorial - Should Silicone Hydrogels be Placed in a Separate FDA Soft Contact Lens Category?". www.siliconehydrogels.org. Retrieved 18 June 2016.
  13. Stretton, Serina (October 2004). "Should Silicone Hydrogels be Placed in a Separate FDA Soft Contact Lens Category?". siliconehydrogels.org. Retrieved 3 September 2020.
  14. "Contact Lens Spectrum - Soft Contact Lenses". www.clspectrum.com. Contact Lens Spectrum. Retrieved 19 Feb 2019.
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  18. "Scout by Warby Parker (90 Pack) Contacts". Warby Parker.
  19. "Miru 1 Day Contacts". LensPricer.
  20. "10.2.4 AONDA Product Page | MyAlcon".
  21. Dr. Karen French (12 May 2008). "The Performance of Galyfilcon A" (PDF). OpticianOnline.Net. Contact Lens Monthly. Retrieved 18 June 2016.
  22. "Dailies TOTAL1® Lens Parameters and Fitting Guide | Alcon".
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  24. Lens Parameters pi.bausch.com Retrieved 30 March 2023
  25. "Bausch + Lomb INFUSE - Optix-now". Optix-now - Your Vision Care Guide. Retrieved 2020-12-23.
  26. "Miru 1month | Menicon America". Menicon America. Retrieved 2021-05-01.
  27. "TOTAL30® Parameters and Contact Lens Technology | Alcon".
  28. "Looking at Silicone Hydrogels Across Generations". www.optometricmanagement.com. Optometric Management. Retrieved 18 June 2016.
  29. Carnt, Nicole (May 2008). "3rd Generation Silicone Hydrogel Lenses". www.siliconehydrogels.org. Retrieved 5 October 2021.
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