Soft contact lens material: Hilafilcon b vs etafilcon a

Hilafilcon b vs etafilcon a: Details and differences between them (Contact lens material part-2). Hilafilcon -b: – The most popular Bausch & Lomb monthly hydrogel contact lens is SL-59. The material of this lens is hilafilcon-b. As per United States FDA classification of contact lenses, hilafilcon-b is a group-2 (High water content, nonionic polymers) contact lens material. DK=22 (Oxygen permeability). High water content means the material contains more than 50% water in the molecule. Hilafilcon-b contains 59% water content. Market available contact lenses are-
  • Bausch & Lomb SL-59 (Monthly disposable)
  • Bausch & Lomb SDD (Soflens daily disposable)
  • Bausch & Lomb SDDA (Soflens daily disposable for Astigmatism)
Etafilcon-A:Etafilcon-a material falls into group-4 of FDA classification. FDA group-4 material means high water content ionic hydrogel polymers. Etafilcon-a contains 58% water and DK value is 28. Market available contact lenses are- 1-Day Acuvue define 1-Day Acuvue moist 1-Day Acuvue moist for Astigmatism 1-Day Acuvue moist Brand Multifocal Acuvue2 Acuvue colours Acuvue Bifocals Naturally 1-Day Multifocal Eyedia Soft What are the differences between ionic and nonionic material? As the surface of ionic materials more negatively charged, so the protein of tear film will be more attracted to contact lens surface. Ionic materials contain carboxylic acids and other acids which are negatively charged and therefore more prone to protein deposit. Whereas non-ionic polymers contain alcohol and amides where the surface charge minimized or surface carries no electrical charged. That’s why protein deposition will be less for non-ionic polymers. Due to this reason, a non-ionic material is better for extended wear (Up to 30 days) contact lenses. Conclusions: – Both the lenses are high water content and almost same water present.  Oxygen permeability is almost same in both materials but etafilcon-a is slightly better. Both materials are good for the daily disposable contact lens. But the protein deposition on contact lens surface will be more with the ionic material. That’s why for better comfort the hilafilcon-b is the better choice for monthly disposable modality than the etafilcon-a.  

Krishnendu Mandal
Optometrist, Blogger, Blogging since Jan 2016

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