Expand Your Horizons: Think GPs for Presbyopes
Thanks to technological advances, multifocal gas permeable lenses are no longer a last resort for practitioners.
By Thuy-Lan Nguyen, OD, Zoeanne Schinas, OD, and Perla Najman, OD
Septemeber 15, 2017
September 15, 2020
Presbyopic contact lens fits are struggling to keep up with patient needs, but new multifocal GP lens technology may be able to reverse this. This lesson reviews multifocal GP lens designs, new technology, and how to incorporate these lenses in everyday practice.
Thuy-Lan Nguyen, OD, Zoeanne Schinas, OD, and Perla Najman, OD.
This course is COPE approved for 1 hour of continuing education credit. Course ID is 54550-CL. Check with your state licensing board to see if this counts toward your CE requirements for relicensure.
This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.
Authors: Dr. Nguyen has a financial relationship with Paragon and the Vision Service Plan.
Dr. Schinas has a financial relationship with the Staple Program and Alcon.
Dr. Najman has a financial relationship with the Staple Program
Editorial staff: Jack Persico, Rebecca Hepp, William Kekevian, Michael Riviello and Michael Iannucci all have no relationships to disclose.
As researchers estimate 22% of our population will be older than 60 by 2050, it’s no surprise our patient population is demanding an ever increasing array of vision correction options.1 Generation X is beginning to struggle with presbyopia, and baby boomers continue to stay in the work force, calling for innovative solutions.1 And although the percentage of presbyopic patients is increasing, presbyopic contact lens fits have struggled to keep up.1 This may be due to a lack of technical knowledge among practitioners, the perception that fitting presbyopes with multifocal contact lenses (MFCLs) takes up too much chair time or concern that MFCLs do not work.
However, recent advances in multifocal gas permeable (GP) lens technology are working to turn this around. This article reviews multifocal GP lens designs, including new hybrid and scleral multifocal options, and how to best incorporate them in everyday optometric practice.
|An inferiorly decentered multifocal GP with excessive movement will cause blurred, fluctuating vision and discomfort.
Why Multifocal GP lenses?
While GP contact lenses only represent approximately 11% of all contact lenses prescribed worldwide and only 9.4% of fittings in the United States, they still offer many advantages over soft contact lenses.2 GP lenses typically provide excellent vision and can be customized for a patient’s individual visual needs, such as modifying add powers and correcting astigmatism, therefore making them a possible lens of choice for astigmatic patients, critical observers, patients requiring good range of vision or depth perception, dry eye patients and those at risk for giant papillary conjunctivitis.
The majority of multifocal GP lenses are simultaneous vision designs, meaning all vision zones (distance, intermediate and near) are within the pupil at the same time. These lenses are available in concentric or aspheric designs. Most multifocal GP lenses are aspheric designs, which have a gradual change in curvature and become flatter towards the periphery to create more plus power. Centration with limited lens movement on blink is critical for proper vision with these lenses, so multifocal GPs typically have larger overall diameters compared with single vision GPs. To provide best possible near vision, aspheric lenses should translate some in down gaze. This allows a greater amount of near plus to enter the pupil zone during near tasks.
Aspheric lens designs can be categorized as front aspheric, back aspheric or bi-aspheric. Front aspheric designs have the power change on the front surface while the back surface is spherical. This reduces spherical aberration and minimizes distortion during lens translation on down gaze. In back aspheric designs, the posterior eccentricity provides a power gradient without inducing corneal warpage. This is an ideal design for astigmatic presbyopes where the toricity is mostly corneal. Bi-aspheric designs allow for more customized control of fit and optics by allowing for precise fit on the back surface and visual correction on the front surface. The ability to correct for both corneal and internal astigmatism can reduce glare and halos, especially in dim lighting, such as night driving.2
|To improve fit and vision for a multifocal GP lens that is decentered with excessive movement, steepen the base curve and increase the overall diameter.
The ideal candidates for aspheric multifocal GP lenses are current GP wearers just entering presbyopia or advanced presbyopes who have significant intermediate vision demands. Patients who spend significant amounts of time using computers placed at arm’s length and eye level may also be successful with aspheric multifocal GPs.
The problems associated with aspheric multifocal GPs typically involve four factors: decentration, excessive movement, insufficient add power and glare. Decentration and excessive movement usually occur at the same time, so solving one typically resolves the other as well. If a lens is decentered inferiorly with excessive movement, it is likely too flat. This will cause blurred and fluctuating vision as well as discomfort. In these cases, steepening the base curve will often improve both fit and vision. Similarly, if a lens is riding high or tucked under the upper eyelid excessively, steepening the base curve by 0.50D should help. This will also prevent corneal distortion. Decentration can also be avoided by increasing the overall diameter, and a larger diameter is recommended for any horizontal (nasal or temporal) decentration.
Inadequate add powers will result in decreased near vision. Newer aspheric designs provide higher adds by increasing plus in the concentric zone on the front surface of the lens.3 Unlike silicone hydrogel soft multifocal lens designs, a slight increase in the near add power of a multifocal GP lens won’t necessarily affect distance vision. For example, if a patient’s spectacle add power is +1.75, a +2.00 add or higher is recommended for their multifocal GPs.
Glare, especially in dim illumination, is a common subjective complaint from patients wearing aspheric designs. Glare typically occurs because the intermediate and near zones are in the pupillary axis during straight ahead distance gaze. Fixing centration is one way to reduce glare and improve overall vision and discomfort. If the lens is well centered and the patient still experiences excessive glare, consider increasing the optic zone diameter. Another potential cause of glare is lens material dryness. Problems with non-wetting can be one of the most frustrating parts of any contact lens practice, and it can also lead to lens deposits and discomfort. Many GP designs are available in high or hyper Dk materials, but the higher oxygen often compromises the wetting angle, so changing to a slightly lower Dk material may improve symptoms of dryness and glare.
|Here, a 49-year-old patient is wearing SynergEyes Duette Progressive lenses. The fluorescein pattern of the gas permeable center shows proper fit with minimal apical clearance throughout while the soft outer skirt provides stability.
One new way to combat dryness and front surface deposits is with Hydra-PEG treatment by Tangible Science. Hydra-PEG, which can be applied to many GP materials and hybrid lenses, is a polyethylene glycol polymer that is covalently bonded to the contact lens surface, creating a permanent wetting surface on the lens.4 Before dispensing lenses with Hydra-PEG treatment, you should advise patients on proper cleaning and disinfection techniques. This includes avoiding any alcohol-based or abrasive cleaners, as they can damage the surface of lens. Instead, try recommending peroxide-based solutions.
Although they are less popular than aspheric designs, translating or segmented multifocal GP lenses are another potentially beneficial option. They rely on proper lower lid interaction with the lens and an upward movement of the lens during down gaze. This allows the patient to see through a different segment other than straight ahead gaze. Translating lenses are typically prism ballasted and can be truncated for additional stability. When fit properly with stable translation, they can offer exceptional distance and near vision. Intermediate vision is a known problem in these lenses, however, so they may not be adequate for computer users who often look straight ahead.3
Problems with translating designs typically revolve around excessive rotation or poor translation. If a lens aligns properly but rotates excessively, it can result in fluctuating distance vision and inadequate near vision. This can be resolved by increasing the amount of prism ballast. Likewise, if a lens is not translating properly, patients will not achieve adequate near vision. To fix this, try flattening the base curve or increasing the amount of prism. Translation can be confirmed by having the patient look down during the slit lamp examination. During down gaze, the lens should shift superiorly so that the near segment rests in the pupillary zone.3 Translation relies on proper lower lid interaction, so patients with loose lower lid tension or lower lids that are positioned far below the lower corneal limbus should not be fit with translating designs.
|A 47-year-old patient wearing an Elara P (Visionary Optics) scleral multifocal GP lens.
Hybrid GP Lenses
For patients who have difficulty adapting to the initial lens awareness of multifocal GP lenses, hybrid and scleral GPs are now available in multifocal designs. Newer hybrid lenses are composed of a high Dk GP center surrounded by a silicone hydrogel soft skirt. In theory, the GP center offers clear vision, while the soft skirt provides good comfort, centration and stability.5 Some of these designs can be ordered empirically with keratometry readings and a spectacle prescription. A key point to remember here is that the GP portion of the lens can correct for corneal astigmatism, so when ordering empirically, start with a distance power that is the spherical component of the spectacle prescription rather than the spherical equivalent. Patients should be properly educated on insertion and removal techniques before dispensing. If the soft portion folds in during insertion, it can cause discomfort. Also, if the patient has problems with dexterity, removing the lens can be a challenge.
The newest category of multifocal GP lenses is multifocal scleral lenses. This broadens the scope of treatment for irregular cornea patients, such as those diagnosed with keratoconus, pellucid marginal degeneration, Salzmann’s nodular degeneration, post-refractive surgery complications, post-penetrating keratoplasty and severe ocular surface disease. Scleral lenses can also provide visual correction for regular corneas with high refractive error or astigmatism. By vaulting the cornea completely and resting on the scleral tissue, these lenses can also offer better initial comfort.6 The continuous tear layer between the lens and the cornea creates an aqueous reservoir that can protect the cornea.7 Thus, scleral lenses are a good therapeutic option for managing ocular surface disease. Patients should be taught proper handling techniques using insertion and removal devices as well as non-preservative saline to fill the lens before inserting.
With so many multifocal GP lenses available, initial lens selection can be challenging, even for expert contact lens fitters. Because every patient is different, no one multifocal GP will work for everyone.
Of course, before choosing a design, a proper refraction, careful slit lamp examination and accurate keratometry reading are necessary. Corneal topography and anterior segment optical coherence tomography are also helpful. However, when it comes to multifocal lenses, patient selection, as well as education before and after fitting, may have a larger impact on patient success.
|Visionary Optics Elara P scleral multifocal is a concentric bifocal design with a near center. Image: Visionary Optics
Practitioners should interview patients about their visual goals, as well as their daily activities. Knowing the specific task a patient wants to be able to do with their contact lenses will better focus and customize their fitting.8 Once the patient’s lifestyle is established, set realistic expectations of vision and wear time. Some patients may have their own preconceived notion of what multifocal GP lenses can do for them, so it is up to practitioners to educate them on the benefits and challenges. Inform patients of the adaptation time required for multifocal GP lenses in advance. It may take a new wearer a few weeks to fully adapt to the initial lens awareness of corneal multifocal GP lenses and the handling of hybrid or scleral multifocal lenses. Success in any of these areas often requires a high level of commitment from both the practitioner and the patient.
Glasses can be worn over multifocal GPs as needed to enhance vision—something that is extremely helpful in certain lighting and during long hours spent on certain tasks. For example, multifocal GPs can provide excellent overall visual results for daily tasks, but when a patient goes to a dimly lit restaurant for dinner, they may need a low plus spectacle prescription to read the menu. Similarly, a patient may experience excellent daytime driving with their multifocal GPs but requires a low spectacle prescription with non-glare lenses for long distance or nighttime driving. In addition, a patient who spends eight to nine hours a day on the computer can achieve comfortable vision with multifocal GPs, but if they need to do any additional computer work at home after hours, they may require a spectacle prescription to enhance near vision when experiencing visual fatigue.
Ocular dominance should be measured for every presbyopic patient interested in contact lenses. While this is necessary for monovision patients, it is also extremely helpful for multifocal patients. A modified monovision prescription with multifocal lenses may be needed to provide adequate vision at all ranges. Simply overplussing the non-dominant eye by 0.50D can have a dramatic effect on binocular near vision without necessarily decreasing distance vision or depth perception.
Prescribing contact lenses for presbyopic patients is a continuing challenge for any optometric practice. While current trends are skewed towards daily disposable and silicone hydrogel lenses, multifocal GP technology also continues to improve.9 Newer multifocal GP designs with more customizable features can prevent problems before they even occur. The explosion of scleral lenses has revolutionized the management of regular and irregular corneas, and with these advances, multifocal GP lenses can once again be the lens of choice for practitioners instead of the last resort.
Dr. Nguyen is an assistant professor at Nova Southeastern University College of Optometry. She lectures, publishes and participates in research on specialty contact lenses. She also recently volunteered her time in the Dominican Republic and Nicaragua to provide eye exams and glasses to those in need.
Dr. Schinas is an assistant professor at Nova Southeastern University College of Optometry, where she teaches several contact lens courses and serves as lab coordinator. She is active in contact lens-related research and has authored abstracts on ocular disease and its management.
Dr. Najman is an assistant professor at Nova Southeastern University College of Optometry, where she has twice earned the “Contact Lens Preceptor of the Year” award. She has published work on ocular disease and contact lenses. Her current research focuses are specialty contact lenses and primary care optometry.
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