what's new in contact lenses?

Navigating the Contact Lens Landscape

Stay competitive by understanding the recent advances and potential opportunities.

Gregory W. DeNaeyer, O.D., F.A.A.O.

Improved technology has advanced the contact lens industry at an exponential rate in the last decade. New materials, designs and solutions have improved patients' vision and comfort. Research and development will continue to propel the field forward, hopefully improving fitting success, safety and utilization.

Contact lens materials

The introduction of hydrogel contact lenses in the 1970s revolutionized the contact lens market. A steady transition to more frequent, planned replacement over the following decades improved comfort, safety and convenience for patients wearing soft contact lenses. The introduction of silicone hydrogels (SiHy) in 1999 had a major impact on comfort, increasing oxygen permeability by approximately five times that of hydrogel lenses.

SiHy lenses have been shown to decrease hypoxic-related complications and there's some evidence that they reduce dryness symptoms in lens wearers as compared to their hydrogel counterparts.^1,2 However, in other respects, SiHy lenses have been somewhat disappointing.

It's been proven that SiHy lenses don't reduce the risk of microbial keratitis (MK) for extended wear (Figure 1).^3,4 Additionally, the relatively higher modulus of some SiHy lenses may increase the risk for superior epithelial arcuate lesions (SEAL) and contact lens-induced papillary conjunctivitis (Figure 2).⁵

Figure 1. Microbial keratitis secondary to contact lens wear

Figure 2. Contact lens papillary conjunctivitis

The next big frontier for contact lens materials is the incorporation of antimicrobial properties. If successful, this may significantly reduce the incidence of MK. To be successful, an antimicrobial additive will have to be nontoxic, provide a broad spectrum of antimicrobial activity and have minimal impact on normal ocular flora.^5,6

Like soft lenses, the gaspermeable (GP) lens industry has developed GP materials with increasing oxygen permeability. Contact lens practitioners routinely prescribe GP lenses with Dks well over 100.

Unfortunately, GP materials can sometimes have poor wettability and be prone to flexure. These negative tradeoffs are especially evident with scleral contact lenses. Practitioners may compensate by having GP materials plasma-treated to improve wetting and increasing the center thickness to prevent unwanted flexure.

Contact lens solutions

The evolution of contact lens solutions has been remarkable over the last 40 years. The industry has come a long way since the days of thermal disinfection in the 1970s. Today, the majority of soft lens patients use commercially available multipurpose solutions that safely clean and disinfect daily wear lenses. Notably, the relatively recent solution-related outbreaks of Fusarium and Acanthamoeba have reminded industry leaders, governing bodies and contact lens practitioners that continued effort and diligence is needed to improve contact lens safety.

The Food and Drug Administration (FDA) Ophthalmic Devices Branch requires testing on a specific panel of bacteria and fungi but does not include Acanthamoeba, a free-living organism which can exist in either a trophozite or cyst form.⁷ However, the FDA is now recommending and researching ways to add Acanthamoeba to the test panel.⁸ This is especially important since the incidence of Acanthamoeba keratitis appears to be on the rise in some areas of the United States.⁸ Recently, the FDA also recommended that manufacturers of multipurpose contact lens solutions remove the “no rub” from product labeling.⁸ This move comes nearly a decade after the first no-rub solutions were introduced. The first obvious advantage to rubbing is that heavy deposits are more likely to be removed with a rub step. This is analogous to dentists recommending that we “brush” our teeth with toothpaste rather than soak or rinse our teeth with a mouthwash. Frictional cleaning, in most cases of hygiene, is a necessary step. In addition, recent studies have shown that multipurpose disinfecting solutions (MPDS) are more efficacious with a “rub and rinse” step.^9,10 Zhu and colleagues¹⁰ reported this year that MPDS that used either polyquad or poly-hexamethylene biguanide in conjunction with two types of silicone hydrogel lenses and one type of hydrogel had the greatest efficacy when incorporating a “rub and rinse” step.¹⁰ Unfortunately, it's been reported that approximately 50% of patients are noncompliant with the rub step.^7,11 In this case, shouldn't manufacturers create products that safely and efficaciously clean and disinfect lenses in a way that is equivalent to a rub-and-rinse regimen?⁷

Three new MPDS have been introduced in the last year including: Opti-Free PureMoist (Alcon), Biotrue (Bausch + Lomb) and RevitaLens (AMO). All three brands tout superior cleaning and disinfection with improved comfort.

Multifocal contact lenses

This year, approximately 11,000 Americans per day will turn 50 years old.¹² The aging of our population is creating an increasing demand for presbyopic correction, which includes patients who prefer to wear contact lenses as opposed to eyeglasses. Presbyopic contact lens patients can be fit into monovision or multifocal lenses in order to lessen their dependency on reading glasses.

Monovision can be successful for many patients and is somewhat easier for the practitioner to incorporate into an early presbyopic contact lens prescription. The downside of monovision is that it only provides a limited range of vision, especially for older presbyopes, and it significantly decreases stereoacuity, whereas multifocal contact lenses provide patients with a continuous range of vision and nearnormal binocular visual function. In addition, the amount of available add power for multifocal contact lenses exceeds the near power that is incorporated for most monovision fits.

Improvements in multifocal contact lens design, for both soft and GP lenses, have dramatically improved the success of this modality. Woods and colleagues¹³ reported in a 2009 study that early symptomatic presbyopes subjective ratings indicated a statistically better performance provided by multifocal correction compared with monovision.¹³ Additionally, fitting multifocal lenses provides significantly higher profits as long as professional fees are set high enough to allow for necessary follow-up care. It makes sent to start most early presbyopes in a multifocal design. A patient in their first symptomatic stage of presbyopia only needs a low amount of add power, which should make it easier to neural adapt to the optics of a multifocal designs. Every year, as their accommodation declines, gradual increases in the add power will be readily accepted.

Contact lenses for the irregular cornea

At no time in the history of the contact lens field have practitioners had such a wide variety of lens modalities to choose from for fitting patients with irregular corneas. It's interesting to consider that not even a decade ago, most contact lens practitioners were limited to using small diameter GP lenses (8.5 to 9.5 mm) to fit patients with keratoconus, penetrating keratoplasty, corneal scarring and refractive surgery disasters. Large diameter GP lenses that range in size from 10 mm to 11.5 mm are becoming more popular for fitting corneas with mild to moderate irregularity. The increased size of large diameter GPs allows them to more evenly distribute lensbearing on an uneven fitting surface (Figure 3). Also, they have less on-eye movement, which improves comfort. U.S.-based GP manufacturers produce numerous large diameter GP designs that can be specific for keratoconus, post-graft or post-refractive surgery. Scleral GP lenses (12.5 mm to 25 mm) are available for fitting patients with moderate to severe irregularity.

Figure 3. Large diameter GP lens on a keratoconus patient.

Scleral lenses have the advantage of bearing on the sclera and vaulting the corneal surface. The tear reservoir that they hold can mask corneal irregularity, but it can also act as a liquid bandage for managing ocular surface disease. Hybrid lens technology has dramatically improved in the last decade. Newer designs with higher Dk materials, stronger soft-GP junctions and a variety of lens geometries are improving fitting success of hybrids for patients with mild to moderate irregularity.

Irregular corneas are usually synonymous with GP lens fitting; however, manufacturers are producing soft lenses that are designed to improve vision for eyes with mild irregularity. These soft lens designs have expanded base curves, diameters and powers that are needed to successfully fit the irregular cornea. Additionally, increased center thicknesses that can run between 0.4 mm to 0.6 mm can mask a significant amount of irregular astigmatism (Figure 4).

Figure 4. A keratoconus design soft lens with a 0.49-mm center thickness

Many practitioners haven't had much experience fitting these advanced lens designs. Fortunately, there are a variety of resources contact lens fitters can take advantage of to help decrease their learning curve. Many of the national meetings offer specific lectures and workshops led by experienced clinicians. The Gas Perm Lens institute (GPLI-www.gpli.info) and The Scleral Lens Education Society (www.sclerallens.org) offers online forums and education resources, webinars and workshops that can benefit contact lens fitters of all levels of experience.

Room for growth

Considering the down economy and the availability of refractive surgery procedures, the question remains—is there room for significant growth in the field of contact lenses? According to the Contact Lens Spectrum 2010 annual report, the United States contact lens market is predicted to grow 6% for 2011.¹⁴ This same article estimates the current worldwide contact lens market to be at $6.1 billion and globally is expected to reach $11.⁷ billion by 2015.¹⁴ The driving force for growth is the development of innovative contact lens products that continue to improve the vision, comfort and safety of contact lens wear. Practitioners should continually educate themselves and embrace new designs and products, which they can introduce to their established patient base. In the United States, one of the biggest potential areas of growth is in daily disposable lenses. The U.S. market share for daily disposables was 13%, which is up from 11% in 2009.¹⁴ The potential for growth of this soft lens modality can be put into proper context when considering the 2010 daily disposable market share in Hong Kong (75%), Denmark (62%), and Taiwan (57%).¹⁶ U.S. manufacturers continue to expand parameters and designs for daily disposables, which will help to allow more patients to take advantage of this lens modality that many find more convenient and comfortable.

Growing a contact lens practice also means preventing decline or contact lens dropout. Richdale and colleagues reported in a 2007 study that the primary self-reported reasons for contact lens dissatisfaction (26.3%) and contact lens discontinuation (24.1%) were dryness and discomfort.¹⁵ Preventing or managing contact lens-related dry eye often involves medically managing dry eye and meibomian gland dysfunction, which is being heavily researched around the world. This will be especially important as the contact lens-wearing population ages.

With advancing technology in contact lens materials, designs and solutions, there has never been a better time to be a contact lens practitioner. The key to growth and improved success involves keeping up with and embracing innovative designs and products. Succeeding with patients who have previously been unable to wear contact lenses, either secondary to vision and/or comfort issues, will generate new patients, as these patients will refer family and friends. Concentrating on internal marketing will help to maximize these potential referrals. OM

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