Contact Lenses

A Compromised Contact Lens Surface Can Compromise Patient Comfort

By John Pruitt, Ph.D.

ADVERTORIAL

Patients don’t want to think about their contact lenses. But with some silicone hydrogel materials, dehydration and deposit buildup can interrupt comfortable lens wear. A compromised lens surface can be at the root of the problem.

There’s more to the surface than meets the eye

While the surface of a silicone hydrogel contact lens may seem static, it’s actually quite an active component. Silicone hydrogel contact lenses contain both hydrophobic (water-repelling) and hydrophilic (water-loving) polymers that move and reorient at the surface during wear1—particularly when exposed to air and tear film changes between blinks.

Exposure to air sets the SiHy surface in motion

Hydrophilic (water-loving) molecules on the contact lens surface rotate inward seeking more moisture.

Hydrophobic (water-repelling) silicone sites rotate outward at the same time. This results in hydrophobic spots on the surface of the contact lens that attract lipids and protein, resist rewetting and may cause discomfort.

A lot depends on the surface dynamics of a silicone hydrogel contact lens. It has been shown that some silicone hydrogel contact lens materials can attract up to 31X more deposits than other available silicone hydrogel contact lens options.2,3 (Fig.1)

Fig 1 – Surface defends against daily deposits

Manufacturers attempt to defend their contact lenses in different ways

Taking a closer look at silicone hydrogel contact lens technology sheds light on different manufacturers’ attempts to protect lenses from dryness and deposits by masking silicone molecules on the lens surface. ACUVUE® OASYS® contact lenses are made of a material containing polyvinyl pyrrolidone (PVP). This binds to water, but does not completely mask the silicone which leads to increased lipid deposits.

With substantial silicone mobility, silicon levels reach approximately 10 percent at the surface of a dry contact lens.6,7 Biofinity® contact lenses are made of a material composed of modified silicone macromers, making the lenses more wettable. However, the lens still allows silicone to be exposed at the surface—attracting lipids that decrease wettability. Silicone remains mobile with large levels of silicon present at the surface (>10 percent) when the contact lens is exposed to air.6,8

PureVision® contact lenses undergo plasma oxidation, which converts surface silicone to silicate “glass.” The surface cracks produce “glass-like” silicate islands. Exposed silicone in the cracks results in high lipid uptake.6,9,10 Lotrafilcon B contact lenses, such as AIR OPTIX® brand contact lenses, feature a unique, permanent plasma surface created by a fusion process. This permanent surface minimizes the mobility of the hydrophilic and hydrophobic sites during blinks by preventing the silicone in the lens material from being exposed to the air.10 This smooth, protective surface allows tears to spread evenly over it, promoting moisture retention and minimal deposit buildup. With surface integrity that lasts throughout the wearing period, less than 1 percent silicon is measured at the surface of a dry contact lens.8

Conclusion

The silicone in silicone hydrogel contact lenses is highly desirable for improved oxygen transmission, but silicone can lead to poor wetting and lipid deposits. Look closer at the contact lens surface to achieve superior deposit resistance, clear vision and consistent comfort.

Trademarks are the property of their respective owners.

Important information for AIR OPTIX® AQUA (lotrafilcon B), AIR OPTIX® AQUA Multifocal (lotrafilcon B) and AIR OPTIX® for Astigmatism (lotrafilcon B) contact lenses: For daily wear or extended wear up to 6 nights for near/ far-sightedness, presbyopia and/or astigmatism. Risk of serious eye problems (i.e., corneal ulcer) is greater for extended wear. In rare cases, loss of vision may result. Side effects like discomfort, mild burning or stinging may occur. Important information for AIR OPTIX® NIGHT & DAY® AQUA (lotrafilcon A) contact lenses: Indicated for vision correction for daily wear (worn only while awake) or extended wear (worn while awake and asleep) for up to 30 nights.

Relevant Warnings: A corneal ulcer may develop rapidly and cause eye pain, redness or blurry vision as it progresses. If left untreated, a scar, and in rare cases loss of vision, may result. The risk of serious problems is greater for extended wear vs. daily wear and smoking increases this risk. A one-year post-market study found 0.18 percent (18 out of 10,000) of wearers developed a severe corneal infection, with 0.04 percent (4 out of 10,000) of wearers experiencing a permanent reduction in vision by two or more rows of letters on an eye chart.

Relevant Precautions: Not everyone can wear for 30 nights. Approximately 80 percent of wearers can wear the lenses for extended wear. About two-thirds of wearers achieve the full 30 nights continuous wear. Side Effects: In clinical trials, approximately 3-5 percent of wearers experience at least one episode of infiltrative keratitis, a localized inflammation of the cornea which may be accompanied by mild to severe pain and may require the use of antibiotic eye drops for up to one week. Other less serious side effects were conjunctivitis, lid irritation or lens discomfort including dryness, mild burning or stinging.

Contraindications: Contact lenses should not be worn if you have: eye infection or inflammation (redness and/or swelling); eye disease, injury or dryness that interferes with contact lens wear; systemic disease that may be affected by or impact lens wear; certain allergic conditions or using certain medications (ex. some eye medications). Additional Information: Lenses should be replaced every month. If removed before then, lenses should be cleaned and disinfected before wearing again. Always follow the eye care professional’s recommended lens wear, care and replacement schedule. Consult package insert for complete information, available without charge by calling (800) 241-5999 or go to myalcon.com.

References: 1. Epstein A, Stone R. Surface and Polymer Chemistry: The Quest for Comfort. Review of Cornea and Contact Lenses. 2010;147(1):15-19. 2. Ex vivo measurement of lipid deposits on lenses worn daily wear through manufacturer-recommended replacement period; CLEAR CARE® Cleaning and Disinfecting Solution used for cleaning and disinfection; significance demonstrated at the 0.05 level; Alcon data on file, 2008. 3. Nash W, Gabriel M, Mowrey-McKee M. A comparison of various silicone hydrogel lenses; lipid and protein deposition as a result of daily wear. Optom Vis Sci. 2010;87:E-abstract 105110. 4. AFM 2.5 x 2.5 micron image; Alcon data on file, 2006. 5. AFM 2.5 x 2.5 micron image; Alcon data on file, 2009. 6. Huo Y, Rudy A, Wang A. Impact of ethylene oxide butylene oxide copolymers on the composition and friction of silicone hydrogel surfaces. Tribol Lett. 2012;(45):505-513. 7. Alcon data on file, 2010, 2011. 8. Alcon data on file, 2011. 9. Zhao Z, Carnt N, Aliwarga Y, Wei X, Naduvilath T, Garrett Q, Korth J, Willcox M. Care regimen and lens material influence on silicone hydrogel contact lens deposition. Optom Vis Sci. 2009;86(3):251-259. 10. Jones L, Senchyna M, Glasier M-A, Schickler J, Forbes I, Louie D, May C. Lysozyme and lipid deposition on silicone hydrogel contact lens materials. Eye & Contact Lens. 2003;29(IS):575-579.

See product instructions for complete wear, care, and safety information.

© 2013 Novartis 4/13 AOA13063AD-A

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