The world of specialty contact lenses is changing so rapidly that the past often appears to be a blur. After only a few months, the newest innovations are seemingly routine and virtually standard-of-care. Think of toric landing zones, hydrophilic coatings, and highly oxygen-permeable materials. All are commonly accepted now.

With so many advances coming one after the other, it’s difficult to know what’s next. Here, we look at some of the technologies that may impact specialty contact lens practice in the next year or so.

MANUFACTURING TECHNOLOGIES

Considerable work is being done to determine how best to make contact lenses with the most precise surface and shape. For example, must lenses always be round? It’s well documented that the cornea is often oval in shape.¹ Would oval lenses be better suited to such eyes? In addition, impression molding techniques have demonstrated that elevation differences often exist between meridians, creating what’s sometimes called a “hyperbolic paraboloid.”¹ What are the best practices to manufacture lenses to fit these various shapes?

Oscillating tool technology has been used to manufacture custom contact lenses for several decades.² With this technology, different radii can be cut without crimping the lens, a technique that was previously required for back-surface torics or bitorics, toric peripheral curves, and front-toric GP designs. Lens designs are no longer limited to radius-defined surfaces; they now can be manufactured in non-symmetrical shapes.

Recently, new milling operations for contact lens lathes have been adapted from the technology used to manufacture intraocular lenses.² With this adaptation, a custom lens is lathe-cut, then the milling tool cuts the diameters into the oval shape required. Data-point programs used with this technology enable greater precision in lens optics and in the peripheral shape of the landing zone.

EMPIRICAL EVALUATION

Much has been written about the importance of scleral shape and how dissimilar it can be from corneal topography.³ Instruments that measure the sclera as far out as 20mm enable us to fit scleral lenses with greater precision and comfort than we could previously through trial and error with diagnostic lenses. Data from these instruments help us select a diagnostic lens to evaluate in situ, noting any necessary adjustments. We can then order a precise, personalized lens (Figure 1).

One downside to diagnostic fitting of scleral lenses, even when enhanced with new data, is that it is time-consuming, particularly when more than one lens is required for evaluation, as each lens must settle for 20 to 30 minutes.⁴ In addition, diagnostic lens sets are expensive, and over time these sets can accumulate in the office, occupying valuable space.

Disinfection of diagnostic lenses has always been a concern, and new guidelines published this year are quite specific and somewhat burdensome.⁵ What’s more, as a result of the COVID-19 pandemic, many patients are rightfully concerned about sterility. They want assurance that they are not at risk for infection during the fitting process.

Fortunately, our need for diagnostic lenses may be declining. New software can import data from profilometers and tomographers to design lenses empirically.⁶ Profilometers typically employ fluorophotometry with fluorescein, while tomographers use a Scheimpflug camera. The software guides practitioners through the program in an orderly sequence, the data are assessed, minor adjustments are made, and the file is uploaded to the laboratory.

By incorporating these data into the manufacturing process, laboratories can make lenses with a high degree of precision. Each lens can be customized to include features such as oval optical zones, limbal curves with different elevations to accommodate the hyperbolic paraboloid shape, and landing zones that follow the contours and tangent angle variations of the sclera.

This technology goes beyond the current generation of quadrant-specific scleral lenses, saving time for practitioners and patients alike. The first lenses dispensed will fit better than any diagnostic lens (Figure 2), resulting in increased patient satisfaction.⁷

EMPIRICAL FITTING: HYBRID LENSES FOR IRREGULAR CORNEAS

A novel method to design hybrid lenses involves using software that creates a three-dimensional (3D) model of the eye and consequent fluorescein pattern with various lens designs and sagittal vaults.⁸ Practitioners send a consultant raw data exported from the topographer. The consultant enters these data into the software to create a 3D model of the eye and a fluorescein pattern. If raw data are not available, a PDF of the topography that lists either eccentricity (e value), shape factor, Q value, or keratometry reading is used to calculate sagittal depth. Using a proprietary calculator, the consultant designs the appropriate lens.

While information can be extrapolated to design a simulated fluorescein pattern with the software, the preference is to use raw data exported from the topographer to obtain a more detailed analysis of the corneal architecture. Various lens designs, base curves, and sagittal depths can be virtually placed on the eye to achieve the desired clearance.

EMPIRICAL FITTING: ORTHOKERATOLOGY

Corneal topography can aid corneal GP lens fitting, as it captures and analyzes corneal shape information in conjunction with lens design software. These platforms use corneal data, including curvature, height, and diameter, to recommend custom lens designs, including orthokeratology lens designs (Figure 3). Practitioners can specify overall diameter, optic zone diameter, and back optic zone radius. A virtual lens may be selected to personalize for an individual patient.

The Arise Orthokeratology System (Bausch + Lomb) is a new approach to managing myopia using orthokeratology. The software fitting system uses a patient’s corneal topography images to recommend a lens design, including the correct landing zone. The system can designate smaller or larger optical zones to meet each patient’s needs. It can also suggest modifications to optimize the lens, choosing from a library of topography images to adjust parameters.

FAR TO NEAR AND ALL POINTS IN BETWEEN

Success for today’s multifocal contact lenses requires more than improving presbyopes’ vision at distance and at near; today’s lens designs also need to enable presbyopes to access the intermediate focal points required when using computers and hand-held devices.

The more recent extended-depth-of-focus (EDOF) designs⁹ create a “cone” of clear, extended focus by adding increasing amounts of plus power to the periphery of a lens. One such design accomplishes this by using a patient’s own higher-order aberrations (HOAs) without exacerbating the inherent ghosting and halos that occur due to coma, trefoil, and the like. These HOAs are thought to account for approximately 10% of the total aberrations in the eye.¹⁰

The purpose of defocusing these peripheral light rays is to create a pinhole effect. Optically, there is no sharp cut-off point as gaze travels from one distance to another. As an added benefit, and unlike centrad designs, EDOF lenses are said to be independent of pupil size.¹¹ Several U.S. manufacturers offer these designs, labeling them as correction for presbyopia. A number of investigators are interested in their utility for myopia control.

Another novel application on the horizon for EDOF lenses involves combining their best features with multifocal designs, as the two approaches may complement each other. While EDOF may be acceptable for intermediate vision and for light reading, sometimes it is not sufficient for extended near work, particularly if fine print is involved. Conversely, current multifocal technologies may not provide a smooth transition from near to the intermediate zone. An ideal lens would fill this void, incorporating both designs to benefit vision at all distances.

A New “Angle” on Multifocal Fitting For any multifocal lens to be successful, the optics must align with the visual axis, which falls upon the center of the pupil. The difference between the pupillary axis and the corneal light reflex is called angle kappa. Technically, we are seeking angle lambda, which is the angle between the pupillary axis and the line of sight. Because the difference between these two is so minimal, they are often considered to be equivalent.

When multifocal optics are not centered over the line of sight, a lens will likely not perform optimally. The result is uncorrected astigmatism and visual distortion. Pupil size, which varies with ambient light conditions, as well as age and miosis at near, come into play. Patients often report double vision or 3D vision, and they may have difficulty finding an appropriate reading distance.

Fortunately, many manufacturers understand these challenges and are providing tools to address them. Some offer different optical zone diameters and the ability to offset the optics to better align with the visual axis. It is well known that scleral lenses tend to decenter inferiorly, because of lens mass, and temporally based on scleral shape. Soft lenses also may be influenced by scleral shape and may decenter temporally, which can be significant given that the visual axis is usually located nasally. So, how do we determine the magnitude of lens decentration?

Most current topographers and tomographers measure angle kappa and pupil size. Many quantify the angle in terms of x and y coordinates. Some models can vary the light intensity to enable us to assess pupil size variations between photopic and scotopic conditions (Figure 4). We can obtain an accurate measurement of the amount of lens decentration and the location of the optical center of the lens by performing topography over the lens in situ. Whether the best image is achieved using an axial (sagittal) or tangential (instantaneous) map depends on the topographer, the calibration settings, and the manufacturer’s or laboratory’s preference. The goal is to visualize the point of maximum power on the lens and its location relative to the visual axis (Figure 5).

SCLERAL LENS CARE

This is an exciting time for practitioners who prescribe scleral lens solutions. A filling solution introduced in January is a physiologic formulation with a pH of 7.4 and an osmolarity of 300. This solution contains electrolytes (calcium, magnesium, potassium, sodium, and phosphate) designed to mimic those in human tears. This formulation is approved by the U.S. Food and Drug Administration (FDA) and comes in single-use 10mL vials, 35 to a box.

VibrantVue Scleral Saline, distributed by ABB Optical Group and Visionary Optics, was FDA-approved in August 2020. This non-buffered 0.9% saline solution comes in single-use 5mL vials, 100 to a box. VibrantVue will be available through eyecare practitioners.

ABB Optical Group and Visionary Optics will also introduce VibrantVue Contact Lens Hand Prep. According to the companies, this hypochlorous technology product is a safe, non-irritating, alcohol-free formulation providing added protection for contact lens users. A study of the formulation demonstrated that it killed 99.8% of human coronavirus in 15 seconds, > 99.9% of adenovirus, and 14 different virulent bacteria within 15 to 60 seconds of contact time. They will also introduce VibrantClean, a clinic/office air and surface sanitizing system using foggers and quart and gallon sizes of hypochlorous acid for effective, non-toxic cleaning, according to the companies.

IMMINENT AND INNOVATIVE SCLERAL LENS PRODUCTS

The stability of scleral lenses makes them an ideal platform for a telescopic system, and various scleral lens designs incorporate a telescopic system for magnification as a form of low-vision rehabilitation.^11,12 These combined scleral lens/spectacle lens systems offer the advantages of reduced weight, improved cosmesis, less conspicuity, and an enhanced field of view compared to hand-held or spectacle-mounted telescopes.

An innovation that generated considerable attention at the beginning of 2020 was augmented reality using contact lenses. The idea that information from our mobile phones can be incorporated into an optical device is intriguing. Manufacturers have been working with spectacles for some time, but many were bulky and unattractive.¹³

One company has incorporated sensing components into an ultra-thin wafer that is applied to a scleral lens (Figure 6).¹⁴ The wafer is fenestrated with micro-perforations so as to not impede the flow of oxygen. Pop-up screens can be accessed by changing the direction of gaze and “dragging” the desired screen into the field of view. When finished viewing the screen, wearers can return it to the periphery in the same manner. In some technical circles, this is referred to as “invisible computing.” Imagine the convenience of not always having to pull out a mobile phone, particularly when engaged in other tasks.

Scleral lenses are an ideal platform for this technology for several reasons. They are stable on the eye, and they have virtually no movement, which means that the image, once acquired, will be stable on the retina.¹⁵ In addition, many patients can wear scleral lenses for extended periods, as the cornea is continually bathed in fluid, and lens desiccation is nonexistent.

A wide variety of information, including current weather, where the closest Italian restaurant is located, and important notifications, can be acquired in this manner. The device will translate language and will be able to provide digital controls for internet-connected devices such as thermostats and smart speakers. The possibilities are vast and ever-expanding.

This technology has important applications for low-vision assistance. For example, near-infrared technology makes it possible for various street signs, such as speed limit and intersection crossing warnings, to come into view. Certainly, this would be helpful for patients who have macular degeneration, but it could also help people who have normal vision when, for example, negotiating a dark parking garage, an outdoor concert venue in the evening, or any number of unfamiliar surroundings.

Companies are now seeking FDA approval of these devices. The first indication likely to be approved will be for low vision.

CONCLUSION

Substantial research is needed to determine best practices for optimal physiology, vision, and comfort for our scleral lens patients. No doubt, these new technologies and solutions will help us improve patient care. CLS

The authors would like to acknowledge the assistance of Keith Parker, Daniel Bell, and Jerome Legerton, OD, MS, in the preparation of this article.

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