contact lens

The Future of Fitting

Predictions and contact lens innovations right around the corner.

Alex Hui, O.D., Ontario, Can.

“ … THE PRESENT IS PREGNANT WITH THE FUTURE,” said French enlightenment writer Voltaire (François-Marie Arouet). In the case of the contact lens market, in particular, this statement fits perfectly (no pun intended). By culling through present contact lens research, demographic and ocular condition data, you can get a pretty good idea of what industry developments and changes to expect.

Here, I provide my predictions based on this information.

Discriminating solutions

The contact lens solution of the future may be very different than that currently on the market today, as the strategy for cleaning and conditioning contact lenses may change. The challenge, of course, is that regardless of how clean or wettable a contact lens is, it is still a foreign, artificial object being placed on the eye. Research reveals the surface of the eye is covered in proteins, lipids and sugars.^1,2

Given these findings, I predict that the solutions of the future may allow removal only of the contact lens deposits which cause ocular irritation and inflammatory reactions, while leaving behind tear components that allow the lens to act most like the rest of the ocular surface. The end result: Issues of discomfort may lessen or decrease as the lens becomes increasingly biocompatible.

As symptoms of dryness and discomfort are the most frequently cited reasons for contact lens dropout, such solutions could make a big difference in enabling many patients to maintain wear.³

Mainstream presbyopic wear

With more and more contact lens wearers becoming presbyopic, many of whom have had a long, successful history of lens wear, contact lens manufacturers have recently begun to focus more of their energies on overcoming the multifocal contact lens challenges (e.g. cost, inadequate vision, limitation in parameters, etc.) to prevent this suddenly very prevalent population from dropping out of lens wear. Keep in mind that the proportion of people older than 60 continues to rise; current estimates are that by the year 2050, this age group will comprise 22% of the population.⁴

Thus, I predict that as these lenses continue to improve and practitioner confidence in their designs increases, presbyopic wear will likely become as mainstream as soft toric lenses have in recent years. In fact, recent surveys have demonstrated that more presbyopic patients are using multifocal lenses rather than monovision as their primary correction, presumably due to improvements in these products' clinical performance.⁴ Recent surveys of contact lens wearers older than age 45 who are wearing some type of presbyopic correction, whether multifocal or monovision, is currently 37%, a figure that will grow as the practitioners in the industry become increasingly comfortable with the products.⁴

Corneal reshaping growth

Myopia is on the rise. In fact, a recent study revealed the prevalence of the condition has risen 66% since the 1970s.⁵ Recent research has implicated sunlight deficiency as a cause of the condition. Specifically, the mechanism of the effect of light has been shown to be mediated by retinal dopamine, which is a known eye-growth inhibitor. The release of retinal dopamine is stimulated by light. Studies have confirmed a consistent link between the time spent outdoors and myopia prevention.⁶

Given the fact that the advent of video games, among other technology, has resulted in less time spent outdoors and will likely continue to result in this outcome as more gadgets and such become available, I predict that the use of contact lenses in children to influence refractive development will achieve greater prominence in the future. After all, myopic parents are interested in how to prevent their children from becoming as myopic as they are, and when given the choice between spectacle and contact lens wear, children opt for contact lens wear.

Already, several parents have consented to have their children undergo overnight corneal reshaping, as the technique has been shown to induce a change in corneal curvature through the migration of epithelium from the central cornea to the periphery, and, thus, slow myopia progression.⁷ It has been suggested that the modified cornea in these patients, with a greater thickness surrounding the center of the cornea, can induce the correct peripheral focus to prevent further myopic eye growth.

Most recently, soft lenses are being investigated as a means of inducing this peripheral defocus, and they are superior to spectacles in this application because they move with the eye, ensuring the correct peripheral defocus is maintained regardless of eye position.⁷

Anti-infection products

We have gained greater insights into the role cleaning solutions, cleaning procedures and the contact lens case play in the incidence of ocular infection, such as microbial keratitis.^8-11 In fact, present research reveals that the importance of the contact lens case in maintaining good contact lens hygiene has only just begun to rise in prominence.

Currently, an antimicrobial contact lens case is available, which includes silver ions.¹² Silver ions impregnated into the case can be readily exchanged for other ions within the solution, such as sodium. In solution, the silver ions work to disrupt the disulphide bonds of bacterial proteins.¹¹ This passive form of antimicrobial activity requires no further action by the patient other than soaking the lens within this specific case.

In this vein, more and more anti-infective modifications to lens materials are being investigated for applicability and compatibility to impart this passive defense, with investigations into coatings of metals, peptides and even molecules blocking bacterial communication currently in the developmental pipeline.^13-15

Disease monitoring

Because research has shown that patients who have a seemingly “normal” intraocular pressure (IOP) can experience IOP spikes and dips throughout the day — unseen by their eyecare professional due to poor timing and the “snapshot” nature of office visits — and periodic IOP monitoring throughout the day for these “normal tension glaucoma” patients is time- and resource-consuming for both the patient and practitioner, researchers are presently investigating the use of contact lenses as a means of acquiring accurate IOP measurements.¹⁶ Specifically, using microfabricated strain gauges embedded into the lens itself, a change in voltage of the strain gauge is linked to a change in curvature of the contact lens, due to an alteration in curvature of the eye through a change in IOP, which is then relayed through a small wire to a monitoring device worn elsewhere on the patient's body. This can then be downloaded by the practitioner at a later time.^17,18 Further work on these devices has been focused on making the lenses communicate wirelessly to the monitoring device while being worn, alleviating the cumbersome nature of wires connected to the eye.¹⁹

In addition, two types of contact lenses that may aid in the monitoring and treatment of diabetes are presently being evaluated. (Research has shown that the glucose content within the tears varies as the glucose content in the blood changes). In one of the lens types, an enzymatic reaction within the lens causes a change in the swelling of the lens that can then be detected by a wavelength shift in the optical diffraction pattern generated from the lens.²⁰ The other lens type links the changes in glucose level to a voltage change within the lens, also induced by the swelling of the lens.²¹ Either lens type could provide relief for the millions of diabetic patients worldwide from the difficulty and pain of regular blood glucose monitoring.

Finally, as research has shown that components within the tear film also change dramatically in certain types of cancers, such as in breast, colon, prostate and lung cancers, using lenses that are able to detect these changes may also be a distinct possibility in the future.^22,23

Drug delivery

The literature has suggested that use of contact lenses concurrent with pharmaceutical use can increase retention time and ocular bioavailability by trapping the drug in the post-lens tear film; moreover, there has been some evidence that drug delivery from the anterior segment of the eye is able to penetrate to the posterior segment.²⁴ As a result, researchers are presently investigating ways in which contact lenses can serve as a reservoir of drug delivery to the eye, allowing for less frequent dosing.

Yet, the greatest challenge to contact lenses as an effective means of drug delivery to the eye is prolonged, extended-release profiles.^25,26 Numerous strategies have been employed by researchers in this field, such as specialized coatings, embedded emulsions and special polymerization strategies for the delivery of anti-glaucoma, antibiotic, anti-inflammatory and anti-allergy medications, all to some degree of success in vitro.^27-33 Already, there is evidence of one such lens for the treatment of allergic conjunctivitis in clinical trials, and lessons gleaned from its eventual release into the marketplace will have a large impact on the future of this field.³⁴

Finally, although contact lenses are already frequently used as bandage contact lenses post-surgically concurrently with topical medications, it seems reasonable to predict that these lenses will be engineered to deliver the complete post-surgical drug regimen rather than the present required frequent dosing. Such a lens would no doubt vastly improve the quality of life of these patients. As a related note, lenses as bandages containing factors, such as epidermal growth factor to promote epithelial regeneration post-injury are being developed.³⁵

Although nothing is set in stone, past contact lens research, demographic and ocular condition data has produced many of the products (e.g. silicone hydrogels, a thriving toric category, etc.) we dispense today. As a result, there's an excellent chance that much of what has been discussed will soon become available. It's important to be aware of what's likely on the horizon, so you can tell patients who aren't able to achieve successful wear today that there's always tomorrow, and tomorrow in the contact lens industry is looking bright. OM

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Dr. Hui is currently a Ph.D. candidate at the Center for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Canada under the supervision of Dr. Lyndon Jones. His work is focused on development of new contact lens materials for the delivery of pharmaceutical agents, and he currently practices part time in Toronto, Ontario. E-mail him at a6hui@uwaterloo.ca.