Human tears contain about 60 different proteins. There are six types of proteins predominate in human tears, immunoglobulins, albumin, transferrin and lactoferrin, lysozyme and tears lipocalin. The tears not only provide protection and comfort for the surface of our eye but also are essential for good vision.
Tear proteins interaction with contact lenses and the adhesion of tear proteins to contact lenses are a major cause of soft contact lens contamination and degradation, wearing problems, decreased lens life and cause cornea inflammation and corneal infection. These eye problems can start to affect vision and comfort adversely. The adherence of proteins to contact lens is depending on the type of contact lens material, tear secretions rate and maintenance of the contact lens.
The FDA categorizes hydrogel lenses into four groupings to evaluate effects of accessory products upon the lens material. Hidrogel lenses with less than 50% water content are considered to be “low water” and more than 50% are “high water.” Less reactive surfaces to proteins or deposits are termed “nonionic” and more reactive materials are labeled “ionic.”
• Group I – Low water, nonionic polymers
• Group II – High water, nonionic polymers
• Group III – Low water, ionic polymers
• Group IV – High water, ionic polymers
Deposition on contact lenses is controlled by the ionic charge of the lens material and water content. Therefore, Group IV lenses are easy to accumulate more protein over time than other groups. These deposits may be protein, lipid, or calcium.
Deposits not only impact the transparency of the lens and the integrity of the lens surface, but they may also challenge the body’s immune system. The ocular system may perceive denatured protein deposits as a foreign body invasion and produce antibodies in response. These cause inflammation and ocular side effects such as irritation, itching, redness, and vision may be somewhat blurred.
Deposits can be avoided by maintaining a good lens care regimen of cleaning and disinfection. Different contact lens solutions work better on different types of deposits. That’s why it is important to always stay with the solutions and care system from your eye care practitioner recommends. Generally, the system was chosen for a reason.
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