This article is from January 2009 and may contain outdated material.
Given that approximately 10 percent of Americans wear contact lenses, most ophthalmologists encounter a few contact patients on any particular workday—whether for an unrelated ocular issue or treatment for complications directly related to contact lens wear.
“Whether ophthalmologists are fitting contact lens patients or not, they need to be informed about contacts so they know what they are doing when they treat these patients,” said James E. Key, MD, clinical professor of ophthalmology at Baylor University and chief of ophthalmology at St. Luke’s Episcopal Hospital in Houston. It is essential, said Dr. Key, for all ophthalmologists to have a basic knowledge of the latest technologies available, the potential risks involved, and how to recognize problems related to contact lens wear.
Super-Permeable: The New Generation of Contact Lenses
Although rigid gas-permeable lenses are still prescribed, especially for patients with corneal irregularities, this group comprises only a small number of the contact lens–wearing population. According to the FDA,1approximately 90 percent of contact lens wearers use frequently replaceable or disposable contact lenses
Refined materials. Multiple materials are used in the fabrication of contact lenses, and all of these affect a lens’ wettability, oxygen permeability, tendency to accumulate deposits, flexibility, comfort, stability and quality of vision. The development of polymers that provide greater oxygen permeability has led to considerable improvement in lens design, according to Peter C. Donshik, MD, clinical professor of ophthalmology at the University of Connecticut in Farmington. “The most exciting innovation was the introduction of silicone hydrogel lenses and the increased menu of parameters available since their initial introduction to the market. We now have parameters available to correct for astigmatism, with a variety of base curves and a good range of powers,” he said.
“And we now have very predictable soft lenses for astigmatism and presbyopia so there is almost no type of refraction that we cannot fit with contact lenses,” added Dr. Key, a past president of the Contact Lens Association of Ophthalmologists.
The benefits of silicone. The incorporation of silicone polymers with the traditional hydrogel lens allows for the passage of considerably more oxygen through the lens to the cornea—six to seven times more oxygen than hydrogel lenses. That was an important breakthrough in terms of eye health and safety, Dr. Key said.
“The silicone has two functions. It increases the oxygen permeability of the lens so the cornea can ‘breathe’ better, potentially reducing corneal stress. Second, there is a connection between infec tion and lack of oxygen to the cornea. The increased oxygen reduces corneal stress, epithelial breakdown and bacterial binding, all of which are risk factors for infection,” he said, adding that one of the greatest benefits of silicone hydro gel contact lenses is that they have enabled a select number of patients to return to 30-day extended or continuous wear prescriptions, a wear schedule that lost popularity during the 1980s due to an associated increase in incidence of keratitis.
Silicone hydrogel contact lenses have quickly become the most popular type of lens as a result of the benefits that they offer, according to Dr. Donshik. “They are the lens of choice for all of my patients who are prescribed an extended wear lens. They also are becom ing the lens of choice for frequent replacement, both biweekly and monthly.”
George A. Stern, MD, in private practice in Missoula, Mont., agreed, “I use a silicone hydrogel in about 95 percent of my lens fits. The only time that I do not prescribe a silicone hydrogel lens is when none exists that would accommodate the patient’s needs. The health and safety advantages over traditional hydro gels are substantial.”
Similar improvements have been made with rigid gas permeable lenses. “These lenses have contained silicone for some time, but they are constantly being improved to allow more oxygen to pass through them into the cornea,” said Dr. Key. Improvements in wearability have resulted in expanded options for patients who are considered difficult to fit, for example, those with keratoconus, astigmatism, dry eye, giant papillary conjunctivitis and presbyopia.
Beware of Contact Lens Complications
While a number of complications are associated with contact lens wear, one of the most avoidable arises when people sleep with their lenses in. This continues to be associated with an increased risk of infection. Researchers at the University of Manchester’s College of Optometry found that “there is a significantly higher incidence of severe keratitis (SK) in wearers who sleep in contact lenses compared with those who only use lenses during the waking hours. Those who choose to sleep in lenses should be advised to wear silicone hydrogel lenses, which carry a fivefold decreased risk of SK for extended wear compared with hydrogel lenses,” according to their report in the British Journal of Ophthalmology.2
Corneal infections associated with contact lens wear are not common, however, said Dr. Key. “Even when we acknowledge that infection is our greatest problem and we are always concerned about an infectious event, it remains, fortunately, a rare problem. The incidence is much less than 1 percent.”
In addition to infections, there are other problems to watch for in contact wearers. Red eye, which can result from lens wear, has a variety of etiologies, including an improper fit, lens deposits, damaged lenses, hypoxia, an allergic reaction to lens care solution ingredients, ocular allergy and dry eye. “You must be able to discriminate contact lens–related problems from those that are not related to lens wear. In general, most are surface problems, infection or allergy. Sometimes discontinuing contact lens wear is the best solution because the patient is just not a good candidate for wearing contacts,” said Dr. Stern.
The Responsible Patient
Selecting the best candidates for contact lens wear is not a trivial task, said Dr. Stern. “Those who exhibit baseline acceptable thresholds of hygiene, age, level of responsibility, intelligence and reasonable eye health that does not indicate any type of contraindication is essential for infection prevention.” But a number of other variables come into play with regard to the development of infection, he added.
“I saw infections more frequently when I practiced in Florida 10 years ago, both when and where infections were more prevalent. The damp environment, in particular, can be an excellent host for the growth of many harmful organisms. We now have a better understanding of why infections occur, and people have changed their practices to eliminate some of those issues.”
“The best way to prevent infection,” said Dr. Key, “is the proper use of contact lens solutions. Some patients do not clean their lenses sufficiently at night before placing them in the cases. Or they reuse or add to the solution remaining in the lens case, which should be a fresh solution every day.” Dr. Donshik added, “One has to be aware of noncompliance. We make sure that patients have a written set of instructions outlining their contact lens care routine. We follow up and make sure that they do not change the lens care products we recommend at the time of fitting because some products may have an adverse effect on the lens.”
“Education is an important part of what we do,” said Dr. Key. “We must teach patients about replacing their lenses frequently and discuss whether we think it is a good idea to wear them overnight or not. Patients also should not leave the office before getting instruc tions about how to care for their lenses properly. If they routinely comply with these steps and use the solutions as recommended, we would not eliminate all infections, but we would see the risk for infection drop much lower than it is now.”
1 Saviola, J. F. Eye Contact Lens 2007;33:404–409.
2 Morgan, P. B. et al. Br J Ophthalmol 2005;89:430–436.
Dr. Donshik has received research funds from Alcon, Bausch & Lomb, Ciba and Vistakon, and has served on the medical advisory boards of Bausch & Lomb, Ciba and Vistakon. Dr. Key has served as a clinical investigator for Alcon and Bausch & Lomb, and has served on the professional advisory board to Advanced Medical Optics. Dr. Stern reports no related interests.
Working With the FDA
Last June the Academy, the Contact Lens Association of Ophthalmologists, the Cornea Society and the American Society of Cataract and Refractive Surgery presented a number of recommendations to the FDA designed to improve contact lens product testing. These recommendations also advocate universal care guidelines for consumers, which ultimately will improve contact lens safety. The care recommendations can be found at EyeSmart.