SILICONE HYDROGEL LENSES
Claims and Outcomes of Safer, More Comfortable Contact Lens Materials
Three contact lens practitioners discuss whether silicone hydrogels are worth all the hype.
By Kathy Shafer
New contact lens materials, particularly silicone hydrogels, represent a rapidly growing segment of the contact lens market. Lenses manufactured from these new materials allow more oxygen to reach the cornea than do traditional hydrogel lenses, a feature that practitioners equate with better ocular health.
Depending on the brand, silicone hydrogel lens claims include improved end-of-day comfort, less subjective dryness than with ordinary soft contact lenses, excellent wettability and sharp, clear vision. These lenses also offer wearing schedule flexibility including the availability of 30-day continuous wear (CIBA Vision's Night & Day lenses). But how do these lenses measure up to their claims in everyday clinical practice?
We spoke to three noted contact lens practitioners: Steven H. Eyler, OD, FAAO; T. Powers Griffin, OD, FAAO; and Loretta Szczotka Flynn, OD, MS, FAAO, (whose combined experience with silicone hydrogels goes back to the early clinical studies on silicone hydrogels) about the performance of silicone hydrogel lenses in practice and whether these lenses are living up to their expectations.
Ocular Health Comes First
As expected, these clinicians all cited increased oxygen transmissibility and improved ocular health as their primary reasons for prescribing silicone hydrogel contact lenses. "Increased oxygen transmissibility (and lack of hypoxia) translates to a healthier cornea," says Dr. Eyler. "The neovascularization that frequently develops at the limbus when patients over wear or sleep in their traditional lenses, though it initially may not prove a significant issue, can result in problems. Less of that neovascularization occurs with silicone hydrogel lenses," he continues. Patient ocular response in Dr. Eyler's practice has been remarkable. "Although we expected the increased oxygen to improve this sign, the extent of improvement and how fast it happens was a nice surprise," he says.
Dr. Szczotka Flynn concurs. "Oxygen is driving everything. I tell even my asymptomatic patients that they're going to be wearing lenses for many years, and even though we don't see any problems now, these new lenses could prevent future problems," she says. "Although I don't necessarily insist on silicone hydrogel lenses for completely asymptomatic patients, I do let them know that a new lens is available and what the alternative can provide."
Dr. Griffin says, "These lenses seem to resolve patient complaints of dry and red eyes." He believes that relieving these types of symptoms will help turn the tide on the contact lens dropout rate and, therefore, strengthen his practice. "The way I see it, it's more effective to switch patients now into better lenses rather than to risk their dropping out of lens wear, leaving us with the cost of attracting new patients to the office," he explains.
Wearing Schedules in the Real World
When Night & Day gained FDA approval for up to 30 days of continuous wear, concerns and discussions about the safety of extended wear resurfaced despite the dramatic increase in oxygen delivery that silicone hydrogel lenses provide vs. previous soft extended wear lenses. Although none of the practitioners interviewed for this article are active proponents of continuous or extended wear, their patients are asking for it. For such requests, practitioners are more comfortable prescribing a lens that has approval for the indication. (Table 1 lists silicone hydrogel brands that are currently available in the United States and their FDA-approved wearing schedules.)
For example, Dr. Eyler says, "I don't promote extended wear aggressively, but if I have a need for it then I want to be sure that my patient can safely and comfortably sleep in the lenses. The approved silicone hydrogel lenses offer that option." He's generally pleased with the results from his extended wear silicone hydrogel patients. Like most practitioners, however, he still expects to see some problems such as ulcerative keratitis. "But, research has shown that the frequency will be much lower than with traditional hydrogels," he says. "However, if a patient wears his lenses too long, then the lenses become dirty and they traumatize the cornea. We still need to preach patient responsibility and to proceed cautiously with extended wear."
Comments Dr. Griffin, "I try to discourage patients from wearing the lenses for the entire 30 days. I still believe that it's better to remove the lenses more often." He instructs his patients to remove their Night & Day lenses every 10 days for cleaning and a one-night break and to discard them at the 30-day mark. "You never know how your patients are really wearing and caring for their lenses, and that's another reason for fitting them with Night & Day," he says. Although Dr. Griffin does fit silicone hydrogels for extended wear about 20 percent of the time, he's still cautious. "I began fitting silicone hydrogels for extended wear thinking that I wasn't going to see any health issues such as corneal ulcers, but a small percentage still occurs. The lenses don't totally eliminate complications. We've had our share of corneal ulcers and abrasions under the lens, possibly because the material is stiffer and it may abrade the cornea a little more than a softer material would," he says.
In her practice, Dr. Szczotka Flynn reports some inflammatory complications among silicone hydrogel extended wear patients, but she hasn't observed any in her daily wear silicone hydrogel patients. She screens out patients who have lid issues, blepharitis or bad lid hygiene. "Among my other patients who've developed inflammation, I observed no signs that would make me think that those patients might develop a problem. I have no screening device that I could have used. Part of my area of research is to try to find such predicting factors, which could involve something that we don't see clinically such as tear composition, corneal topography, how the lens drapes the eye in the periphery or other factors that we can't see behind the slit lamp," she says.
Interestingly, Dr. Szczotka Flynn also says that most patients who ask about extended wear are teens and their parents. Parents know that their teenagers fall asleep with their lenses in place and are concerned because it's not likely to stop. Such patient behavior is apparently even more common than we previously expected. A 2003 CIBA Vision study of more than 9,000 North American soft lens wearers revealed that 28 percent of patients who wear one- to two-week, low-Dk/t disposable lenses occasionally or routinely slept in their lenses overnight. A subsequent consumer study (also by CIBA) in March 2004 among North American soft lens wearers indicated that 84 percent of wearers nap in their lenses and more than one-third do so frequently or all the time. (CIBA Vision data on file for both studies.)
Dr. Eyler comments, "I lean more toward daily wear, but it's naive to think that patients don't sleep in their lenses occasionally, even if you do prescribe them for daily wear. Our job is to understand this and to protect them as much as possible," he says. Appropriately approved silicone hydrogel contact lenses can help you do this.
Discomfort or Dryness?
Among the benefits that daily wear silicone hydrogel products offer is improvement in end-of-day comfort. Many practitioners and patients mentally relate end-of-day discomfort to dryness, but Dr. Szczotka Flynn doesn't agree. "These patients don't have dry eyes. It's more of a discomfort that many of us and our patients call dryness because we don't know what else to call it." She adds, "I do think that silicone hydrogel lenses have a claim in this area. They decrease discomfort in several ways, some of which are probably dryness-related, some are oxygen-related and some could even be design-related." Whatever the combination of factors, she's pleased with the results and moves existing patients who complain of end-of-day discomfort or "dryness" and who have any redness at all into silicone hydrogels.
Dr. Eyler finds that silicone hydrogels are "a better option for marginally dry eye patients who've always struggled with late afternoon discomfort and eye drops. With these lenses, either because of a more wettable surface and/or increased oxygen and healthier corneas, these patients' symptoms don't seem as significant. They report that they can wear the lenses longer with a better comfort factor in a daily wear regimen." He also says, "Patients who have chronic low-grade red eye, whether from dryness, lack of oxygen, over wear or not discarding lenses as directed, find that their eyes are just a little whiter with silicone hydrogels. I hear patients comment with some frequency, 'My eyes seem brighter and a little whiter.'"
Silicone hydrogel lenses seem to relieve patients' dry eyes and redness in Dr. Griffin's practice as well. "Probably for nine out of 10 patients that we switch, we find that their eyes feel more comfortable and less dry. Their eyes look whiter and they're happier."
Choosing Among Silicone Hydrogels
Some features somewhat direct lens choice among the available silicone hydrogel products. Obviously, as we've discussed, if a patient is going to sleep in the lenses, then the extended wear approvals become paramount. Dr. Griffin chooses the highest Dk available for such patients. In a daily wear regimen, fit and patient comfort/preference become key, and available parameters greatly influence the choice. As Dr. Eyler notes, "If a patient needs a higher prescription, then you're limited. If he's hyperopic, etc., then the parameters dictate the lens choice. When the lens moves and fits well, we go with it."
Dr Eyler also sees advantages that may apply to daily wear for children. "These lenses handle great and are durable, which is an advantage for parents, too. When you're fitting a sixth-grader, you want a lens that's healthy, durable and handles well, and silicone hydrogels meet those needs."
Dr. Griffin points out a particular benefit of one brand: "If a patient has a history of cataracts or a family history of cataracts, I fit Acuvue Advance (Vistakon) first because it provides UV protection."
Pros and Cons
Our three practitioners all agreed that silicone hydrogel lenses provide good, clear optics, which may result more from the lens design than from the material. However, Dr. Griffin did comment, "Oftentimes patients achieve better vision than they had in other modalities because the silicone hydrogel material stays cleaner and the surface doesn't dry out. It doesn't tend to collect deposits as quickly as older materials. I've received many positive comments about the vision with these lenses."
Have these practitioners experienced any issues specific to silicone hydrogel materials? So far, just a few. Dr. Eyler mentioned that most silicone hydrogel materials are more rigid than traditional hydrogels. "Some patients feel it's simply not as comfortable as their usual lens. Also, because we currently have limited base curve selections, the lenses may not fit properly," he says. Dr. Griffin agrees. "It's a different material with a higher modulus, and sometimes patients just can't get past those first few days when they may feel it more than their previous contact lenses."
Dr. Szczotka Flynn has also seen some ortho-k-like changes occur in a few higher myopes, with evident corneal flattening and prescription changes as much as 1.00D. However, those are extremes. "Some patients' prescriptions change a little, but their topography doesn't really change. We think that these patients are just regressing back to their baseline myopia after the potential edema from their low-Dk lenses has cleared. I haven't seen any patients go the other way and increase in myopia."
The Future of Silicone Hydrogels
How confident are these practitioners in this new category of contact lenses? Extremely. In fact, Dr. Szczotka Flynn fits most of her new contact lens patients in silicone hydrogels if they fall within the available parameters, and she's moved more than 60 percent of her existing wearers to them as well. "We just need more lenses with expanded parameters, plus torics and multifocals. The ultimate would be a daily disposable high-Dk lens, but I think we're a long way from that," she says.
Dr. Griffin is enthusiastic. "It's exciting -- these lenses have rejuvenated the market. Silicone hydrogels have attracted new patients who come to the office asking about them, and they've brought many patients back into lens wear who had previously dropped out because of comfort problems. Patients who've never found lenses comfortable have surprised themselves by doing as well as they have. The lenses have pulled a number of these patients back into the contact lens field," he says. But he currently fits only about 20 percent to 30 percent of patients with these lenses. "I would fit more, but they're not available in enough parameters yet," he says.
Says Dr. Eyler, "A year-and-a-half ago, I was fitting five percent or less of my patients with silicone hydrogel lenses, but today I fit 20 percent to 25 percent and that number is going up exponentially." He continues, "In about two years, it's likely to be more than 50 percent. As lens parameters expand and torics and bifocals become available, they'll take over the market as long as we can get the same results visually. I believe that's about five years out."
Have silicone hydrogel lenses thus far delivered on the expectations of safety and comfortable vision? Let a couple of our participants have the last words.
"When companies come out with a brand new lens, they tend to over promise and what happens in the real world often is a little bit off. In the case of silicone hydrogels, it hasn't been that far off. I've been pleased with how well all of the silicone hydrogel lenses have worked," says Dr. Griffin.
Dr. Eyler concludes, "Though we still have no absolutes and no ultimate problem-solving lens, silicone hydrogels are changing the landscape of contact lens care. These new lenses are fantastic."
Ms. Shafer is an independent marketing consultant and freelance writer. She has over 25 years marketing experience in the medical/surgical device industry including 10 years in contact lenses and ophthalmic devices.
Dr. Eyler practices primary care optometry in a group practice in Charlotte, NC. He is the current president of the National Board of Examiners in Optometry.
Dr. Griffin is part of a group practice that has three locations in California. He's participated in numerous clinical trials for new contact lens designs and materials for several contact lens companies.
Dr. Szczotka Flynn has been in clinical practice for 12 years with the Department of Ophthalmology, University Hospitals of Cleveland, as director of the Contact Lens Service. She's also an associate professor at Case Western Reserve University and is an FDA clinical investigator.