Contact Lenses And Giant Papillary Conjunctivitis
Soft contact lenses have undergone a quantum increase in technology since the introduction of the first silicone hydrogel lens in 1999. Today we are on the third generation of these lens materials and undoubtedly we will see improvements over the next few years. Silicone is highly permeable to oxygen and is used to allow a healthy level of air to reach the corneal tissue below.
In the early years of soft contact lenses, the investment for a single par was high (well over $1000.00 at todays cost), and patients and their optometrists did everything they possibly could to extend the life of these lenses. Lenses were often sent away for a “deep cleaning” to a special ophthalmic company. Since the same pair of contact lenses were often reused for 3-4 years, they became very coated with deposits of lipids, proteins, and mineral from the wearers own tear film. A type of reaction known as GPC (giant papillary conjunctivitis) became fairly common. The contact lens wearer would present at their eye doctors office with complaints of lenses sliding around in the eye with frequent adherence under the upper eyelid. Their eye would be red with itching and mucous discharge coating the lenses. When the optometrist flipped the upper eyelid inside out, large papillae or red bumps would be seen.
The Contact Lens GPC Vanishing Act
In 1987 the first disposable contact lens heralded a drastic drop in cases of GPC for the rest of the century. With frequent replacement of contact lenses deposits were no longer significant developments. In 1996 daily disposable lenses appeared on the eyecare scene and helped the small number of patients left that still cultivated significant lens deposits within a few weeks. Contact lens induced giant papillary conjunctivitis was becoming an eye disease of the past.
New Silicone Hydrogel Contact Lenses And The Reappearance of Red Eye GPC
With the introduction of silicone hydrogel contact lens materials, extended wear of lenses started growing in popularity once again. While uncommon, GPC started to be seen again on occasion. Why? To answer that question it is important to understand what causes GPC. While eye research is not conclusive, GPC is probably caused by antigenic and / or mechanical issues. Antigens are substance that create an inflammatory response from the body through the production of antibodies. Deposits of your own tear film components on a contact lens may invoke an autoimmune response where the eyelid tissues reject the substances naturally found in your tears. Mast cells develop in the surface layer of cells underneath the top eyelid. Mast cells release histamine which creates the itchy red eyes. The upper eyelid tends to overlap a significant portion of the contact lens and this is exactly where the problem occurs. As the papillae, or bumps develop under the upper eyelid, the surface area of the mucous secreting goblet cells increase resulting in more discharge. When the mucous starts being secreted the lens often sticks to the upper eyelid. As the lens rides under the upper eyelid it produces some mechanical bumping and friction to the tissues underneath. This is probably where the increase in giant papillary conjunctivitis from todays silicone hydrogel lenses originates.
Contact lenses have a physical component referred to as the modulus of elasticity. The modulus of elasticity measures how much a contact lenses resists being deformed by a physical force. It means more or less what it sounds like, how floppy the contact lens is. A higher modulus means the lens is stiffer. When silicone hydrogel lenses came on the market they were fairly stiff compared to traditional soft contact lenses. While this did not translate into any discomfort, it did mean there was more interaction with the upper eyelid. The modulus of elasticity has been measured in the past for some of the silicone hydrogel lenses as follows:: Acuvue Oasys: 0.7, Bausch & Lomb Purevision: 1.1, Optix O2: 1.2, CIBA Focus Night & Day: 1.4, and Cooper Biofinity: 0.8. For comparison, the old Acuvue 2 was between .3 and .4. There are other factors to account for including the surface properties of the lens material. These help determine how freely lenses glide under the eyelid, and also how deposit resistant their surface is.It is likely that the cases we see in the new silicone hydrogel lenses are due to mechanical irritation on the underside of the eyelid. Since the contact lenses are more rigid one would expect to see an occasional case of giant papillary conjunctivitis.
The mainstay of treatment of any allergic reaction is limit the exposure to the offending allergen. With contact lenses this usually means reducing the replacement cycle or removing the lenses every day. A number of different eye drops are used for problem eyes, usually drops that stabilize the mast cells and prevent the release of histamine. With the advent of once a day drops, contact lens wear is rarely interrupted. These drops are very safe and often used on an ongoing long term basis.
Innovation in the contact lens industry today is leading towards new materials that are much more flexible. The recent market addition of the Acuve TruEye has added the daily format to the new silicone materials. At some point you can expect the low incidence of GPC to fade away to levels unheard of in the past.