Article

TECHNOLOGY IN YOUR PRACTICE

Contact lenses of the future are not as far off as you might think.

Contact lenses of the future are best understood in the context of the Law of Accelerating Returns.1 This law holds that human knowledge, a subset of intelligence, expands geometrically rather than linearly. Some proponents of Singularity, a school of thought that embraces the Law of Accelerating Returns, hold that in 100 years, we will know 25,000 times more than we know today. A linear model would say that we will know 100 times more, while a diminishing return model forecasts that we will know less than 100 times more.

The field of contact lenses is no different from other domains. Fifty years ago, the nascent industry produced single-cut, non-GP rigid lenses. Today, we have elegant one-size-fits-nearly-all low-modulus, hyper-Dk soft lenses that are cast molded at about 2% of the cost of the lenses from 50 years ago. Our knowledge and our technology of materials, processes, ocular contour, impact on physiology and anatomy, lens design, and lens care products validates the Law of Accelerating returns decade by decade over the last 50 years. The next decade (and the next 50 years) will continue a compounding of this advancement.

Component-containing contact lenses are expected to contain basic as well as complex processors at a low cost made possible by the continued improvement in density of integrated circuits, the increase in the number of instructions per second, and continued increase in computation power per dollar.

SO, WHAT WILL THE FUTURE BRING?

We recently entered the era of component-containing lenses along with the era of technology-driven prescribing. Future contact lenses will embrace both of these domains. Advancements in material science, lens manufacturing processes, micro-electro-mechanical systems (MEMS), micro-optics, and nanotechnology are contributing to advanced passive and electronically active contact lenses.

Advancements in instrument-driven ocular contour measurement, algorithm-based calculating systems, and fit assessment technology will enable artificial intelligence (AI) systems in the contact lens practice. Machine learning is science-based and requires defined input and algorithms to produce an output. The AI systems will capture the clinical data input and otherwise non-explicated mental manipulations of today’s skilled contact lens practitioners. The art of contact lens prescribing has evolved to become the science of contact lens prescribing by way of instrumentation that measures more and with greater accuracy and repeatability. Prescribing systems and methods will continue to be better articulated while also being data- and evidence-based. As such, AI systems will become widespread in clinical practice.

AI systems are not a significant requirement for one-size-fits-all products at the practitioner level. They may well be used as “practitioner replacements” (think self-refracting at the consumer level). Future contact lenses will target new indications that will be different as they emerge.

Component-containing lenses present some development challenges. The components themselves, as well as the lens substrates and designs of component-containing lenses, are forecast to require higher modulus or may exhibit added component stiffness and greater thickness profiles while maintaining state-of-the-art comfortable edge profiles. Lens stiffness is understood in engineering to be proportional to the third power of the relative thickness when the modulus and design are otherwise constant.2 That said, the wonderful forgiveness in fitting the low-cost, cast-molded lenses of today may be challenged in the early part of the era of component-containing lenses. The fortunate confluence of technology-driven prescribing and the use of AI systems will be useful to reduce chair time and assure high first-time lens success rates in the context of the need for greater attention to the lens-to-eye relationship.

The AI systems will also be useful in the practice of corneal refractive therapy and in the fitting of rigid scleral contact lenses and custom soft contact lenses for corneal rehabilitation, for presbyopia, for refractive error regulation including myopia prevention and control, and super vision in the well patient/healthy eye practice.

NEW INDICATIONS FOR FUTURE CONTACT LENSES

The presently known use cases for contact lenses of the future are sensing ocular physical-mechanical changes, sensing of molecular components in the eye, imaging of ocular components, virtual and augmented reality content delivery, drug delivery, presbyopia and super vision, and refractive error regulation.

Contact Lenses Containing Physical-Mechanical Sensors The era of component-containing lenses was ushered to commercialization by a first United States Food and Drug Administration (FDA)-approved lens that includes a strain gauge and sending unit that measures changes in corneal volume3 (Figure 1). The changes represent an analog to intraocular pressure changes. The lens is made of a medical grade silicone elastomer and is molded to include the strain gauge and electronics. The FDA market clearance of this single-use lens that is worn in the open and closed eye for 24 hours was a milestone for contact lenses of the future. We now have a commercialized lens that contains micro-machined metal and active electronics.

Figure 1. Contact lens with strain gauge sensor.
Courtesy of Sensimed AG

There are other physical-mechanical changes that will be sensed by contact lenses. Several of these will be discussed later in the article.

Contact Lenses Containing Chemical Sensors The tear film is a rich source of information about ocular and systemic health. Multiple contact lens development efforts are underway to produce a blood glucose level-sensing contact lens (Figure 2) for the more than 30 million people in the United States, and more than 425 million worldwide, who have diabetes. The first market clearance in this category will be a milestone for the molecular-sensing category in contrast to the physical-mechanical sensing category. Antigen and toxin concentrations, micro-organism concentration, blood alcohol, inflammatory mediators, and other systemic health markers may be useful to measure with future “lab-on-a-lens” contact lenses made possible by the materials, components, and processes used in the first sensing contact lens. The lab-on-a-lens has great potential to be part of the technology-driven precision medicine of the future.4

Figure 2. A blood sugar sensing mechanism.
Courtesy of Medella Health

Multiple patents are published that include contact lenses with cameras for the purpose of inward and outward imaging5,6 (Figure 3). One inward camera use case cited is iris recognition for personal security when the wearer is accessing information. The inward camera could also be used for health monitoring and precision medicine. For example, a contact lens gonioscope could be used in clinical practice and for managing angle closure glaucoma.

Figure 3. From the patent for Sony’s camera contact lens.

An envisioned outward camera use case is for recording what users’ eyes see. The outward camera contact lens suggests applications for law enforcement, defense, industry, and for the visually impaired. A video recording of what is in front of the line of sight is one step beyond a body camera for law enforcement personnel.

Contact Lenses for Virtual, Mixed, and Augmented Reality Content Delivery Several analysts forecast the domain of eyewear and headsets for virtual, mixed, and augmented reality to reach retail sales from 10 million to 100 million units by the end of 2020.7-9 The first significant product launches of virtual reality (VR) headsets occurred before the year-end holiday season 2016. In the first quarter of 2017, and after four months of sales, Sony announced that it had exceeded its own forecast with the sale of nearly 1 million units at an average sales price of approximately $500.

The second category to come to market is mixed reality (MR); with this, virtual/digital content is simultaneously viewed with normal real-world vision. Mixed reality will be followed by augmented reality (AR), in which the virtual content can be fixed or registered to the real world in three dimensions and moves with the real world upon gaze change.

Advanced VR and MR systems, as well as all AR systems, will use eye tracking. The majority of the approximately 50% of consumers who need a refractive correction will benefit from spectacle lenses or contact lenses behind the virtual reality headsets. However, spectacle lenses interfere with eye tracking systems. As a result, users will be better served to wear contact lenses when using VR, MR, and AR headsets that incorporate eye tracking. The growth of VR, MR, and AR is therefore expected to stimulate an increase in the number of new contact lens patients.

VR headsets are bulky and heavy because they contain the expected geometric optics that must be between the eye and the display to provide clear focus (Figure 4). The lens power is often more than +20.00D because the displays are closer than two inches from the lenses. The VR systems need as large an aperture as possible to provide the desired field of view of 90º or more. As a result, the lenses are large, thick, and heavy. Versions of the headsets designed for use with special contact lenses could be much less bulky and lighter in weight.

Figure 4. Geometric optics in a virtual reality headset.
Courtesy of Jay Marsh

A contact lens-enabled wearable display system funded by the Defense Advanced Research Projects Agency, the National Science Foundation, and the National Institutes of Health uses novel filter technology and a central microlens to deliver vision of the real world and vision when viewing a near eye display with a focal demand (Figure 5). These contact lenses are engineered for use with VR, MR, and AR eyewear. The contact lenses allow for the elimination of the optics in the respective display eyewear. Reference design display eyewear is therefore lighter and more stylish (Figure 6). The eye is free to look in all directions of gaze, which allows for a field of view that is only limited by the display size itself. The contact lens is rotationally stabilized and contains one or more fiducials that reflect the light from one or more gaze trackers mounted on the inside of the eyewear (Figure 7). The electronics and processing of this type of gaze tracker in the display eyewear is simplified in contrast to pupil tracking technologies.

Figure 5. A contact lens with display and non-display paths.
Courtesy of Innovega Inc.

Figure 6. Mobile virtual reality contact lens-enabled eyewear.
Courtesy of Innovega Inc.

Figure 7. A contact lens with fiducial for gaze tracking.

Research of published patents indicates other efforts for display contact lenses that do not require the need to use display eyewear in combination.5,10 While standalone display contact lens technologies are orders of magnitude more difficult, remember the Law of Accelerating Returns and the continued increase in the density of integrated circuits, the increase in computation power per dollar, and the increase in instructions processed per second.

The recent accomplishment of a five-nanometer chip with 30 billion transistors that is forecast to be 40% faster while using 75% less power will continue Moore’s Law once again.11 Such a chip—with low power use, high processing capacity and speed, and a thickness of only a few atoms—offers great potential for contact lens applications.

Drug Delivery Contact Lenses Future contact lenses will be need-based and not a solution looking for a problem. There is a need for time release of ophthalmic medications to increase their efficacy and decrease ocular and systemic side effects from high initial dosing. The eye’s structure and biochemistry make it highly impervious to drug penetration and retention. It is estimated that the uptake of a pharmaceutical dispensed to the tear film ranges from 1% to 5%. There is also a need to improve compliance to increase efficacy and overall patient wellness. As early as 1970, contact lens industry pioneer Neefe12 filed a patent application for contact lens drug delivery.

Multiple strategies for contact lens drug delivery are in development. Research on drug-eluting contact lenses is focusing on increasing the duration of drug release through molecular imprinting, dispersion of barriers or nanoparticles, increasing drug binding to the polymer, sandwiching a poly(lactic-co-glycolic) acid (PLGA) layer in a lens, developing novel materials, and the use of either passive or active microfluidic systems.12 The active systems may employ advances in electronic components and could incorporate a sensing-to-processor controlled release loop.

One research group is concentrating on the value of lysozyme in the tears to serve as a release mechanism. One product development effort uses a hydrogel contact lens embedded with bio-responsive gels that contain a glaucoma drug. The gels consist of nanodiamonds coated with polyethyleneimine, which are cross-linked to chitosan. When lysozyme cleaves to chitosan, the gels break down and slowly release the drug over a 24-hour period. The nanodiamonds do not break down when stored in saline.13

Bengani and colleagues reviewed research on contact lens strategies for the controlled release of antibiotics, anti-inflammatories, glaucoma therapy, and dry eye therapy.14 These strategies with hydrogel and silicone hydrogel contact lenses incorporate a variety of technologies including Vitamin E loading, molecular imprinting, superficial solvent impregnation, micro- and nanoparticle dispersion such as dimyristoyl-phosphatidylcholine (DMPC) liposomes, the use of surface-immobilized layers of liposomes, and ionic interactions.14

The development challenges for drug delivery contact lenses include maintenance of shelf life of a preloaded drug delivery contact lens, the adverse effect from light exposure due to photosensitivity of pharmaceuticals, and the impact of sterilization on the novel materials due to variations in thermo-expansion and transition temperature sensitivity.

Future Contact Lenses for Presbyopia and Super Vision Custom soft lenses continue to present an opportunity for the industry to do a better job with management of presbyopia. The geometric diversity of human eyes combined with the variance in pupil size and the reality that soft contact lenses do not center over the visual axis result in a wide range of visual outcomes with otherwise well-designed and -manufactured low-cost, cast-molded lenses. The future holds the opportunity for precision simultaneous vision soft lens products and methods of fitting. The spectacle lens industry continues to deliver progressive addition lenses and methods of fitting to improve visual outcomes and the quality of life of patients. The contact lens industry will do the same.

Center-near multifocal contact lenses induce coma when they are displaced from the visual axis. Technology-driven fitting methods for measuring lens displacement from the visual axis combined with pupil size and reactivity measurements will drive higher success rates with multifocal contact lenses.15 The polish-free computer numerically controlled (CNC) lathes of today and the future will continue to improve the ability to manufacture decentered center-add designs in soft, hybrid, and scleral lens modalities.

The same CNC lathes are now able to produce rotational asymmetric contact lens designs to the circumference of the lenses. The result of this technology advancement is the ability to manufacture a lens that does not have to be planar or round. In other words, it is no longer a necessity to manufacture a lens that is round or a lens that has equal elevation at the edge when it is round. This technology enables mold and lens manufacturing that could produce a successful translating soft or hybrid lens. Precision simultaneous vision and translating multifocal soft and hybrid contact lenses are expected in the future and may capture a significant share of the growing specialty contact lens market.

Accommodating contact lenses represent a more natural presbyopia correction due to the optical and mechanical limitations of monovision, simultaneous vision, and translating optic designs. Electro-active accommodating contact lenses are in development by multiple teams.16,17 The products are expected to employ fluid meniscus or liquid crystal technology (Figures 8 and 9). The accommodating contact lenses will also employ one or more means of sensing the need or effort to accommodate. These include sensing convergence, pupil size decrease coupled with convergence, accommodative demand by distance to an object of regard, and several other methods claimed in published patent applications.18-20

Figure 8. Fluid meniscus contact lens for presbyopia.

Figure 9. An accommodating liquid crystal contact lens.
Courtesy of Johnson & Johnson Vision

Magnante and others envisioned and anticipated a method of clinically measuring and incorporating submicron optical features for higher-order aberration (HOA) correction with contact lenses.21 Additionally, Marsack et al are demonstrating a reduction in HOAs through the fitting and manufacturing of scleral lenses with HOA features.22

The first use is expected to be for patients who have high HOAs from their irregular corneas. This technology is expected to advance to expansion-free soft lens form factors for the greater population of patients who have regular corneas and want to reach for their super vision potential of 20/10 or better.

Future Contact Lenses for Refractive Error Regulation and Light Therapy Many large and small manufacturers are strategically focusing on myopia prevention and regulation. The FDA conducted a workshop to obtain input for guidelines for clinical investigations of the new indication of myopia control.23

The primary device of focus in that workshop was peripheral defocus soft contact lenses, but the audience showed interest in corneal reshaping as well. Additionally, pharmaceutical intervention with low-concentration atropine, along with peripheral defocus and the importance of time outdoors, was recognized by the American Optometric Association in its recently published Pediatric Eye and Vision Examination.24 These guidelines serve as a standard of care when treating a child who has myopia.

Customized peripheral defocus soft lenses present a theoretical opportunity to achieve a higher level of efficacy compared to one-size-fits-all designs. As these data become more compelling, an increasing number of future peripheral defocus contact lenses will be individually prescribed based on the respective peripheral refraction measurements of each eye and the measured pupil size. Visual axis alignment may prove to be important for optimized progression control.

A meta-analysis of reported studies of soft lens use for children is reported by Bullimore.25 In that study, the safety is summarized as equivalent to reports for other age groups. An increase in the frequency of children and adolescents wearing soft contact lenses for refractive error regulation is forecast. Many of these lenses may be customized for optic zone diameter, peripheral defocus optics, and visual axis alignment.

The significant number of studies showing the efficacy of corneal reshaping for regulating the progression of myopia have all been conducted without an effort to modulate the posterior lens design to produce a desired peripheral add.26 As a result, lower-treatment-target eyes achieved a corneal shape with a lower add while higher-baseline-myopia eyes enjoyed a higher add post-treatment.

Designs will emerge that include features to provide independent peripheral add control for each central corneal refractive target. These contact lens designs will also allow for modulation of the chord diameter of the add to attempt higher regulation efficacy respective to individual average pupil size. Modern CNC lathes and advancing understanding of corneal contour provide the ability and insight to design corneal contact lenses with controlled centration. In this manner, the optimized optics may also be more closely aligned to the visual axis.

Outdoor light replacement strategies may be incorporated into contact lenses by way of 3D printed quantum dot light emitting diodes (LEDs) in a contact lens27 (Figure 10). Patents are issued for electromagnetic radiation refractive therapy.28,29 The use of programmable light sources can control the chromaticity, direction, duration, and amplitude of light to the retina for the purpose of regulating the progression of myopia. This technology could be used in conjunction with an open-eye peripheral defocus contact lens or a closed-eye corneal reshaping contact lens.

Figure 10. A quantum dot LED contact lens.
Reprinted with permission of Kong YL, Tamargo IA, Kim H et al. 3D Printed Quantum Dot Light-Emitting Diodes. Nano Lett. 2014 Dec;14:7017-7023. © 2014, American Chemical Society.

In the same manner, light sources in contact lenses are anticipated for the regulation of mood disorders including seasonal affective disorder.30 The light sources emit the proper wavelength of light and brightness to stimulate the intrinsically photosensitive ganglion cells that radiate to downregulate melatonin and upregulate serotonin (Figure 11).

Figure 11. A regulated light source contact lens for seasonal affective disorder.

TECHNOLOGY FOR PRESCRIBING CONTACT LENSES OF THE FUTURE

Component-containing contact lenses of the near future are expected to require technology in the clinic to optimize the lens-to-eye relationship because of the forecast higher lens stiffness and, in some cases, to provide the biomarkers for features to stabilize and center the lenses. Precision simultaneous vision and translating soft and hybrid lenses will become easier and faster to fit with higher first lens success rates by the use of instrument-driven data. Full ocular contour measurement is already a clinical need for scleral lens prescribing, and that instrumentation is available. Peripheral refraction and pupillometry provide the basis for optimizing peripheral defocus soft lens prescribing for each eye and drive the lens design for corneal reshaping lenses for myopia control.

The number of aberrometers in use is reaching a critical mass that will accelerate to market single-vision and multifocal lenses that incorporate correction of, or optimization for, HOAs.

Clinical programming of active electronic component-containing lenses may be required in the same manner that audiologists program hearing devices for individual needs. This programming is expected to be in a wireless fashion while patients are wearing the lenses.

Emerging contact lens and instrument technologies will change the course for a growing number of prescriptions. Low-cost cast-molded lenses will retain good market-share as the total number of wearers increases due to the new reasons to wear contact lenses and the new use scenarios and indications. We have exciting times ahead. CLS

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