Factors to Consider when Selecting Patients for Silicone Hydrogel Lenses

The “do nothing, leave well enough alone” approach to contact lens practice, while not a growth strategy or particularly beneficial to patients, is the path of least resistance in many contact lens practices. The clinician in a busy practice has time to deal with the big problems: get everyone’s vision sharpened up and take care of acute problems, but may not go the extra step to offer patients their most ideal treatment options. Another reason for lack of change is that eyecare practitioners can be a conservative lot. It is the nature of our gate keeper role to actively protect the patient from unproven new technologies until we gain experience with them and feel that the benefit to the patient is appreciable and the value is proven.

Our conservative leanings were best expressed at a British Contact Lens Association meeting in Brighton, England in the late 1990s. A poll of eyecare professionals at that meeting showed that they would feel most comfortable prescribing silicone hydrogel lenses for overnight wear if they were first able to see the results of 7 years of clinical research on the lenses. Seven years of research!! Those of us in the contact lens clinical research trenches were somewhat discouraged at that tremendous amount of work. It was hard to imagine that we’d ever have seven years of clinical experience in hand, but now in 2004 that is the reality.

What have we learned about patient selection in those years of research and interaction with practitioners? The question of patient selection has two parts. The first consideration is which type of patient to fit with these lenses regardless of wearing schedule. The second is which wearing schedule works best for various types of patients. With silicone hydrogel lenses that are approved for up to 30 nights of wear the practitioner prescribes both the lens and the wearing schedule for each patient.

Part 1: Which Patients Benefit From Higher Oxygen Transmission?

All patients, regardless of their current wearing schedule, can benefit from higher oxygen transmission through their contact lenses. The level of atmospheric oxygen is the upper limit of desirable oxygen transmission for human eyes. Higher oxygen transmission can help patients with neovascularization, corneal swelling and the resultant myopic creep, and the redness that can accompany use of low Dk hydrogel lenses. It also seems to help alleviate some late day symptoms that are driven by hypoxia.

Patients with Symptoms at the End of the Day : Late day symptoms of discomfort and dryness that are often reported by hydrogel soft lens wearers are significantly reduced when patients begin to wear silicone hydrogels. In a recent study, we found that these symptoms were more frequent and severe among DW patients than EW patients with low Dk hydrogels. Over 30% of DW soft lens patients reported moderate to severe end of day dryness with their low Dk lenses at the beginning of the study. After only 1 week in silicone hydrogel lenses, only 13% reported that degree of end of day dryness. The EW patients began that study with fewer symptoms (14%) than their DW counterparts and half of them reported reduced end of day dryness by the 1 week visit. (Chalmers 2004) (See Figure 1)

Figure 1

Patients with Limited Wearing Time : Relief of end of day symptoms of discomfort and dryness should have an impact on contact lens dropouts and may well help retain lens wearers. Two large studies have shown that symptoms of dryness are related to discontinuation of lens wear. (Doughty 1997, Begley 2001) Even a small reduction in the number of patients who subsequently abandon lens wear will have a very positive impact on contact lens wearers around the world.

Neovascularization : A large study with over 6,200 patients recently found that neovascularization was the most common pre-existing ocular finding that practitioners noted among patients who were being fitted with silicone hydrogel lenses for 30 nights of continuous wear. Another study found that 18% of daily wear patients and 24% of extended wear patients in low Dk lenses presented at baseline with neovascularization (Chalmers 2004). Neovascularization responds well and quickly to the increase in oxygen delivered through silicone hydrogels. With Dumbleton and the group at the CCLR in Waterloo, Ontario we found that neovascular vessels empty quickly after switching to silicone hydrogel lenses and do not refill over time (Dumbleton 2001).

Chronically Red Eyes : The study that examined the ocular signs with EW and DW with low Dk lenses found that 30-35% of patients in low Dk hydrogels had some degree of limbal redness and 35-40% had conjunctival redness. A number of research teams have shown that chronic contact lens related ocular redness decreases rapidly with the use of high Dk silicone hydrogels. Patients appreciate this benefit as a visible sign of better biocompatability. (Chalmers 2004) (See Figure 2)

Figure 2

Patients Considering Refractive Surgery : Your thirty-something patients who are considering refractive surgery often voice their frustration with the daily cleaning, disinfection and handling of their contact lenses. Practitioners who offer these patients continuous wear silicone hydrogel lenses have found that the patients appreciate the ease of use and round-the-clock vision they have without giving up the ability to fine tune their refractive prescription through their presbyopic years. How often do patients’ prescriptions change from the age of 40-60? The permanent change in refractive error offered by refractive surgery only addresses the patients’ refractive needs at one point in time. Unlike refractive surgery, the power of silicone hydrogel lenses can be changed as often as necessary through years of wear to keep up with the demands of their changing presbyopia.

With silicone hydrogel lenses for continuous wear your 40 year old low myopic spectacle wearer can have a chance to experience “permanently” corrected distance vision and the potential pitfalls of that distance correction. It is so much better to run this refractive exercise with the reversible treatment of silicone hydrogel lenses rather than permanent refractive surgery. Some patients may realize that they depend on their uncorrected vision for many of their household tasks and you can alter their lens power accordingly through monovision correction with contact lenses.

Part 2: What Factors Should be Considered when Choosing the Patient’s Wearing Schedule?

Many eyecare professionals approach their silicone hydrogel practice by prescribing 30 nights of continuous wear for all patients who desire that wearing schedule. Those patients who don’t find this wearing schedule comfortable and easy to maintain will then self-select out of that wearing schedule. The studies I have been involved with show that the patients who cannot maintain a continuous wearing schedule do so most often due to mechanical comfort issues that might be addressed with a different lens design or due to symptoms associated with an inadequate tear film. Patients who discontinue use of silicone hydrogels tend to be younger patients.   In addition patients who reported excellent satisfaction (9-10 on a 10-point scale) with their previous hydrogel lenses were more likely to discontinue lens wear compared to patients who reported moderate satisfaction with their hydrogels. (McNally 2003)

Allergic Patients : Atopic patients may find that they can’t maintain their 30 night wearing schedule during all months of the year. During the seasons with highest pollen counts, allergic silicone hydrogel wearers find relief by switching to a DW regimen and cleaning their lenses each night. After the pollen months are passed, patients can resume an overnight wear schedule. A discussion with the patient during the fitting and followup exams will help to determine a patient-specific wearing schedule that enhances their success with silicone hydrogel lenses. Allergic patients will really appreciate the flexibility of wearing schedules that silicone hydrogel lenses offer.

History of Ocular Inflammation : Contact lens wearers with a history of ocular inflammation such as contact lens peripheral ulcer (CLPU), corneal infiltrates or contact lens acute red eyes (CLARE) should be cautioned about continuous wear. Patients who have had inflammatory events with contact lenses have an added risk of experiencing another similar event if they continue with a 30 night wearing schedule (McNally 2003).

Figure 3

These patients should be advised that a shorter overnight wearing schedule may be a better choice in order to reduce that risk. Like all patients, they should be advised to remove lenses immediately and call their practitioner if their eyes become red or feel worse than normal.

Dry Eye Patients : Patients with non-Sjogren’s dry eye can often wear silicone hydrogel lenses on a daily or flexible wearing schedule. After a thorough discussion that sets the patients’ expectations, these patients can proceed with a DW wearing schedule. Avoidance of preservative containing lens care systems is important to keep these patients’ tear film as stable as possible.

Avid Swimmers : The issues surrounding water contamination of lenses are no different for wearers of silicone hydrogel lenses. The need to disinfect lenses after they have been exposed to fresh water or chemically treated pool water makes a continuous wear schedule difficult for people who swim regularly. Use of a powerful alcohol cleaner along with their disinfection system is advised for patients to use for their after-swimming lens care regimen.

In summary, many types of patients will benefit from silicone hydrogel lenses and the added oxygen supply to their eyes. With this new technology eyecare practitioners have the opportunity to engage their patients in a proactive discussion of a new technology. This doctor-patient discussion can set appropriate expectations with the patient and demonstrates the scientific pros and cons that the practitioner has considered in order to customize the wearing schedule and choice of lenses for that individual patient.
Chalmers RL, Dillehay S, Long B. Barr JT, Bergenske P, Donshik P, Secor G, Yoakum J. Impact of previous extended and daily wear schedules on signs and symptoms with high Dk lotrafilcon A lenses. (Submitted to OVS, 4/29/04 or could cite 2004 BCLA Paper of same title)

References: Begley CG, Chalmers RL, Mitchell GL, Nichols KK, Caffery BA, Simpson T, DuToit R, Portello J, Davis L. Characterization of ocular surface symptoms from optometric practices in North America. Cornea;20(6):610-618(2001).

Doughty MJ, Fonn D, Richter D, Simpson T, Caffery B, Gordon K. A patient questionnaire approach to estimating the prevalence of dry eye symptoms in patients presenting to optometric practices across Canada. Optom Vis Sce 1997;74(8):624-31.

Dumbleton KA, Chalmers RL, Richter DB, Fonn D. The vascular response to extended wear of hydrogel lenses with high and low oxygen permeability. 2001 Optom Vis Sci, 78, 3 Volume:78,147-51.

Chalmers RL, McNally JJ. Baseline wearer-reported factors associated with development of corneal infiltrates with silicone hydrogel lenses for continuous wear: An interim report. 2004 IOVS 45: S4, p 65.

McNally JJ, Chalmers RL, McKenney CD, Robirds S. Risk factors and reasons for discontinuation of wear as reported in a post-approval evaluation of 30 night continuous wear contact lenses. IOVS 2003; 44: S5, p153.

McNally JJ, Chalmers RL, McKenney CD, Robirds SR Risk Factors for Corneal Infiltrative Events with 30 Night Continuous Wear of Silicone Hydrogel Lenses. Eye & Contact Lens; 29(1) S153-156(2003).