HYBRID LENSES

The History of Hybrid Contact Lenses

Where these lenses started and where they are today.

By Roxanna Potter, OD, FAAO

Most practitioners would agree that each contact lens modality has advantages and disadvantages. For example, while soft lenses generally offer immediate comfort and great centration, GP lenses can often provide superior optics and visual acuity in many patients.

Naturally, the search then begins for an alternative or a combination of the two modalities that will maximize the advantages of each while minimizing their less desirable properties.

The practice of “piggybacking” has existed for more than 40 years and is still used today. Though not a true hybrid design, wearing a soft lens under a GP lens can improve comfort and stability while retaining the optical qualities of a GP lens, particularly when fit on an irregular cornea.

However, patients may struggle with the cost of multiple lenses and with the extensive care and maintenance required of this system. Piggybacking can also lead to the deleterious effects of reduced oxygen transmission, such as corneal edema and neovascularization.

So while piggyback systems have been used successfully, they also have drawbacks, and a better combination of GP and soft lens properties is highly desirable.

Alternatively, scleral contact lenses are garnering much excitement currently, but they are still relatively new in both design and understanding. Ongoing questions about fogging, peripheral scleral toricity, optimal sagittal depth, and more all continue to present challenges with this modality in some patients.

With the ultimate goal of excellent optics, comfort, and stability, hybrid lens innovation and improvement have occurred from the birth of this idea to today; it is an important lens modality to consider for many patients. Hybrid designs have undergone a steady evolution that has allowed us to experience effective improvements in lens fitting success. The evolution of hybrid designs has been both extensive and fascinating, with ongoing research and development that every day brings us closer to the optimal combination of hard and soft contact lenses.

Early Generation Designs

The first truly hybrid technology, patented by two scientists (Charles A. Erikson and Amar N. Neogi), was acquired by Precision Cosmet Co., Inc. in 1977. Named the Saturn II lens, it gained U.S. Food and Drug Administration (FDA) approval in 1984.

The concept was quite novel in that it was not simply a GP lens “attached” or glued to a soft lens skirt, but a molecular interweaving of the two different materials. Unfortunately, due to the low-Dk material and limited parameter options, the original lens often resulted in complications from tight fit and poor oxygen permeability.

While not tremendously clinically successful, the lens did show promise as an option for patients unable to wear the currently available GP or soft contact lens designs, so Sola Barnes-Hind, Inc. purchased the technology and redesigned it with additional parameter options using a more advanced manufacturing process.

The next-generation SoftPerm hybrid contact lens was more customizable and, therefore, more comfortable; however, issues of low Dk, lens tightness, adherence, and flexure persisted. Practitioners noted frequent and significant eye health issues from ongoing wear of this lens, including redness, infiltrates, edema, neovascularization, and epithelial erosions. Complaints of lens separation at the junction between the soft and GP materials and of breakage were common as well. Despite two later revisions of this lens, it remained infrequently used but nonetheless available until its discontinuation in 2010 (Ferguson, 2012).

Modern Design Developments

In 2001, Quarter Lambda Technologies Inc. (the predecessor to SynergEyes, Inc.) began to develop the next hybrid lens, which received FDA approval in 2005. The company’s SynergEyes lens had many significantly improved properties. The central GP portion had a higher Dk, and a patented technology called Hyperbond kept the GP and soft portions of the lens securely connected. Improved wettability of the soft skirt and a larger range of customizable parameters allowed for a better lens wearing experience.

Four variations on the SynergEyes lens covered conditions including astigmatism (SynergEyes A), keratoconus (SynergEyes KC), post-surgical (SynergEyes PS), and presbyopia (SynergEyes Multifocal). The next few generations of design continued to build on this foundation of hybrid theory.

Though significantly improved over earlier attempts, some issues remained with this line of lenses. Low-Dk skirt materials, limited use beyond mild-to-moderate severity of keratoconus and other irregular cornea conditions, tight fitting characteristics, and challenges in removal of the lenses required further research and development. Despite such issues, these four initial designs proved useful for many patients.

Expanding on the range of keratoconus and other irregular cornea conditions that could be fit in a hybrid, the next hybrid lens designs took advantage of the growing interest in sagittal depth, rather than base curve, as the primary fitting parameter (a concept that is now fully established in other GP lens and irregular cornea lens modalities, such as scleral lenses). The ClearKone design utilizes a complete corneal “vaulting” premise via reverse geometry to provide minimal, but complete, apical clearance that may help avoid corneal touch, improve tear flow, and reduce excessive lacrimal lens effects on vision.

Further design developments also followed for regular corneas, with the release of the Duette line for spherical and astigmatic patients. These lenses addressed the low-Dk skirt concern in previous hybrid lenses. They have a silicone hydrogel skirt with a Dk of 84 and a central GP lens Dk of 130. This lens is a possible choice for patients who have regular astigmatism and may require better stability, acuity, or more custom parameters than can be achieved in soft toric designs, or for those who may be unable to tolerate corneal GP lenses.

The Duette line also offers two multifocal options. One utilizes a simultaneous design, with an “Add Zone” similar to the original SynergEyes multifocal lens. A more recent design eliminates the zonal add premise and instead utilizes a center-near multifocal concept.

Case Study #1

A 33-year-old white female presented complaining of poor vision and comfort in her current soft toric contact lenses. Best-corrected acuity with a refraction of +7.25 –2.25 x 165 was 20/20 OD and with +7.50 –2.00 x 028 was 20/25⁺² OS. Topographies showed regular astigmatism but fairly flat keratometry readings of 40.50/43.37 @ 076 OD and 40.75/43.25 @ 098 OS.

Initially, a refit into a silicone hydrogel toric design was attempted, but the patient was still bothered by rotation and unstable, blurry vision. Duette lenses were then ordered empirically in parameters of 8.3mm base curve (BC), flat skirt curve (SC) and +7.50D OD and OS.

Upon dispense, the patient’s acuities were 20/20 OD, 20/20 OS, and 20/20⁺² OU. On slit lamp, the fit showed good corneal and conjunctival alignment with no bearing at the junction (Figure 1). She reported good initial comfort and was trained on application/removal and hydrogen peroxide-based solution use.

Figure 1. Elements of proper Duette lens fitting include GP alignment (A), no junctional bearing, conjunctival alignment without impingement (B), and good centration (C).

After two weeks of wear, she returned for follow-up noting excellent acuity and stability of vision, good comfort over 12 to 14 hours of wear each day, and good adaptation to the new lens application/removal and cleaning regimen.

Case Study #2

A 51-year-old white male presented complaining of poor vision in his current soft toric monovision contact lenses. He reported frequent rotation and blur, which was all the more obvious when combined with the visual compromises already characteristic of monovision. His refraction was –0.25 –4.00 x 109 (20/20) OD and –0.50 –4.25 x 082 (20/20) OS with a +2.00D add. Topographies showed regular corneal astigmatism.

He initially requested a refit into custom soft toric lenses, but found that they exhibited the same problems that he had noted previously, despite attempted adjustments to diameter and base curve.

Duette Progressive lenses were ordered empirically with parameters of 7.5mm BC and 8.7mm SC OD and OS. Powers were –0.50D OD and –0.25D OS with a +1.75D add. The patient quickly adapted to the new application/removal techniques, and after a few weeks of wear and adaptation returned with visual acuities of 20/20 OU at distance and 20/25⁺² OU at near. On slit lamp, the lenses demonstrated good fitting characteristics. He reported stable vision and better depth perception. At his next routine exam one year later, he was still satisfied with his lenses.

Current Offerings

By combining fitting characteristics of the ClearKone design and the material characteristics of the Duette line of lenses, the UltraHealth lens (the newest hybrid design) is appropriate for a number of corneal conditions due to its hyper-Dk GP center, high-Dk silicone hydrogel skirt, and variable vault system for clearance over many corneal irregularities.

The lens should be fit with apical clearance that, after settling, is adequate but minimal (approximately 50 to 100 microns). This is possible due to characteristics of the midperipheral GP and peripheral skirt fitting properties that create a tear pump effect during lens wear. This differs from other lenses (particularly scleral designs) that can require hundreds of microns of clearance due to minimal tear exchange under the lens throughout the day.

Rather than GP lens alignment or a fully skirt-supported scleral bearing, the UltraHealth lens is fit to clear the central cornea, bear slightly on the midperipheral cornea at the GP “inner landing zone,” and align the skirt with the conjunctiva to help provide centration and edge comfort without needing any lens support or lifting effect from the sclera.

The UltraHealth lens does require online training/certification and fitting set utilization; a standard fitting set and a flat curve (FC) fitting set are currently available. The FC design is the same as the original UltraHealth, but with flatter central base curve options, making it more appropriate for some patients who have oblate corneas to obtain ideal corneal clearance. This can include post-refractive surgery patients, those who have “sunken” grafts, or those who have pellucid marginal degeneration.

Case Study #3

A 54-year-old white male presented for a comprehensive eye examination complaining of ongoing comfort issues with his scleral contact lenses. His ocular history included longstanding pellucid marginal degeneration OD>OS. He reported intermittent redness and discomfort, dryness, and midday fogging OD and OS. Though still the best contact lenses he had tried to date, he was curious as to whether there were any new options that did not require midday removal and reapplication to maintain comfort and vision during his long and busy work days.

His spectacle refraction was OD +0.50 –1.25 x 100 (20/20^-1) and OS –1.00 –0.50 x 080 (20/20), with a +2.25D add OD and OS. Figure 2 shows his topography maps. He was refit into the UltraHealth lenses OD and OS by utilizing the standard fitting set. The first lenses tried had vaults of 250 microns and skirt curves of 8.4mm (Flat), which after settling exhibited complete but slightly excessive corneal clearance.

Figure 2. Topography of Case Study #3 showing pellucid marginal degeneration. The right eye (A) is worse than the left eye (B).

Desiring less sagittal depth, a lower vault was chosen (150μm). This lens demonstrated the ideal fluorescein appearance, and the patient noted good comfort. With over-refraction and a power adjustment to allow for monovision correction (OD near), lenses were ordered.

After a few weeks of wear, the patient returned noting good overall vision but difficulty with end-of-day comfort and removal OD. The skirt curve was adjusted to the Flat2 option OD, and after another trial period the patient reported good comfort and vision with final parameters of vault 150, Flat2 skirt, –1.75D (MV) OD and vault 150 microns, Flat skirt, –3.50D OS. Final visual acuity OU was 20/20 at distance, 20/25⁺¹ at near.

Practitioner-Friendly Policies

Previous generations of hybrid lenses were often used as a last resort for patients who failed in other modalities, making them the ultimate in “specialty” lens fitting. Unfortunately, this limited their practicality and use in many practices, as they were higher in cost and had limited warranty/exchange periods.

With the increased success of newer-generation hybrids, patient demand has grown, and practitioners have access to more forgiving policies. Current hybrid designs are priced competitively and offer “risk free” exchange, return, and shipping policies. This can help increase patient loyalty and satisfaction and helps promote practice growth and profitability. New hybrid designs also now come with assistance from customer service and consultation staff, online ordering options, and patient education materials.

Ongoing Challenges

Despite significant developments over the last decade, we can expect even more hybrid advancements in the years to come. Some of the more interesting possibilities include further improvements to materials and designs to allow for better end-of-day comfort, parameter expansion to allow for even more customized fitting, and multifocal designs for irregular cornea patients. This last idea would be particularly intriguing as an option for the growing post-refractive surgery and newly presbyopic patient base.

Ongoing challenges to hybrid designs include the lack of front-toric options for lenticular or residual astigmatism and the unique and sometimes difficult-to-master techniques for lens removal.

As is the case with virtually every other lens modality, ocular surface disease is an ever-present challenge that should be addressed prior to lens fitting. The current six-month replacement schedule can also cause issues, particularly in patients who are prone to heavy deposits or who are irresponsible with lens care and compliance.

Another challenge is the lack of any other competitors in the hybrid market, though this doesn’t seem to have prevented SynergEyes from continually trying to improve their lenses and business model.

While no modality is capable of being the ultimate lens in fit, vision, and comfort for every patient, it is important to remember that newer hybrid designs are significantly different from their predecessors. In addition, future hybrid lens development may address many of these current concerns.

Old, bad experiences and prejudices from Saturn and SoftPerm history no longer apply, and there has never been a better time to try the hybrid modality.

Formerly a “lens of last resort,” hybrids can now be considered a “lens of first choice” and should be included in any practitioner’s arsenal of contact lens options for both regular and irregular cornea patients. CLS

Special thanks to Janet Stein, COT, FCLSA, of SynergEyes, Inc. for her assistance with this article.

To obtain references for this article, please visit http://www.clspectrum.com/references and click on document #240.

Dr. Potter owns a private practice in Sylvania, OH. She enjoys fitting, writing, and lecturing on specialty contact lenses. Dr. Potter has received travel expenses, stipend, or reimbursement from the STAPLE Program, and lecture or authorship honoraria from the STAPLE Program and the GP Lens Institute. She can be reached at rpotter@personaleyecare.com.