A Hydrogel System for the Correction of Presbyopia

Bruce A. Bridgewater, O.D., Barry Farkas, O.D. & Frank Toscano, O.D.
April 1999

This article surveys the use of the UltraVue system of lenses, which offers a method of correction for all stages of presbyopia.

For many years, practitioners have been frustrated by the lack of a predictable contact lens correction for presbyopia. A deficit in practitioner-confidence is reflected in recent Health Products Research data, which suggests that less than one percent (approximately 300,000) of all contact lenses sold in the Unites States are of a bifocal or multifocal design. This minimal activity is remarkable, considering that the largest segment of the contact lens wearing population is or will become presbyopic within the next few years, a fact that offers a tremendous opportunity to savvy contact lens practitioners.

A multitude of hydrogel bifocal or multifocal contact lens designs are currently available. These designs range from aspheric to annular to multizone designs. Some manufacturers also promote the use of differing designs or combinations of designs for varying degrees of presbyopic correction.

The UltraVue System

The UltraVue contact lens system is a unique, multifocal technology that incorporates spherical and aspherical optics to provide for distance, intermediate and near vision for myopic, hyperopic and presbyopic refractive needs.

As schematically illustrated in Figure 1, the UltraVue system incorporates two contact lenses with complimentary and reverse geometry designs. The UltraVue P (add in the periphery) is designed for the dominant eye and offers 20/20 distance and 20/24 near visual acuity. Worn on the non-dominant eye, the UltraVue C lens (add in the center) is designed to offer 20/40 distance and 20/20 near visual acuity.

As seen in Figure 2, UltraVue P lenses are designed with a spherical central zone that promotes sharp distance visual acuity. The central zone is surrounded by an aspheric, annular zone that creates a gradual refractive shift toward plus power and offers intermediate and near visual function. As previously mentioned, practitioners should expect and, if necessary, problem-solve for 20/20 distance and at least 20/40 near visual acuity.

As seen in Figure 3, UltraVue C lenses are designed with a spherical central zone that promotes sharp near visual acuity. The central zone is surrounded by an aspheric, annular zone that creates a gradual refractive shift toward minus power and offers intermediate and distance visual function. Practitioners should note and problem-solve for at least 20/40 distance and 20/20 near visual acuity.

The Monovision Difference

With the UltraVue system, the disparity in visual information is kept to a minimum and contact lens wearers should note little, if any, affect on their binocular function. Conversely, monovision requires an innate ability to suppress visual information and its inherent disruption on binocularity, which has been widely reported. While monovision appears to be reasonably accepted in early presbyopia, the compromises of monovision becomes substantially less tolerated as the disparity between the two visual images increases. The UltraVue system is unique in that lens design modifications can be utilized to maintain the minimal (20/20 -20/40) disparity throughout all stages of presbyopia, thereby promoting continual efficacy.

UltraVue Fitting

The UltraVue system is surprisingly easy to fit. The following will highlight the simple concepts and steps necessary to empirically fit these lenses. Table 1 provides an example of empirical fitting.

* Parameters -- Figure 4 shows that the UltraVue lenses are available in a wide array of parameters. Each design can be generated with three base curves with distance powers ranging from +20.00D to -20.00D, add powers from +1.00D to +4.00D in 0.50D steps, and three central zone diameters.

The lens diameter is held constant at 14.5mm. All lenses are generated from the Benz 45G hydrogel polymer, which is a low water content (48%), nonionic material that has been reported to offer low on-eye dehydration and limited deposition. All lenses also incorporate a blue handling tint.

This wide array of parameters offers an unusual ability to enhance visual performance. In addition to adjusting the distance lens powers, practitioners can also adjust add powers and central zone diameters to promote visual performance. In essence, practitioners can alter near visual performance without affecting distance vision, just as they can alter distance vision without affecting near vision (binocularly).

* "The 20/20 - 20/40 rule" -- As previously discussed, each design is intended to provide a certain level of visual performance at all viewing distances to maintain the integrity of the system as a whole. Providing the projected visual acuities are met (UltraVue P: 20/20 distance and 20/40 near, and UltraVue C: 20/40 distance and 20/20 near), contact lens wearers should note 20/20 distance and near vision with little, if any, degradation in binocularity.

This intended visual performance level ("the 20/20 - 20/40 rule") can be utilized to ensure appropriate lens selection and to quickly identify when and where a system may not be properly functioning.

* Candidate selection -- Current contact lens wearers are the most obvious choice for multifocal designs, as they are motivated to continue enjoying the advantages of contact lenses. They are also familiar with the insertion and removal techniques and the care requirements of contact lens wear.

However, practitioners should be careful not to prejudge patients without a history of contact lens wear. In particular, hyperopic presbyopes can often be extremely motivated to initiate lens wear. Until presbyopia, this patient group has most likely enjoyed distance and near vision without correction and are now dependent upon a correction for all viewing distances.

This unique system employs elements of simultaneous vision and some decrease in contrast is possible. While not reported by most subjects, patients with very demanding visual tasks and expectations may note some mild contrast reduction, especially during the first few days of contact lens wear. Generally, standard ranges of pupillary zone diameters do not correlate to success or failure with this design. If, however, pupils are unusually small or large, the system's projected visual goals may not be met.

Key indicators of success with the UltraVue contact lens system are normal binocularity, refractive cylinders of 0.75D or less and a full-time distance and near visual correction.

* Eye dominance -- To function as a system, practitioners must first determine eye dominance. While there are many eye dominance testing techniques available, we recommend a +2.00 fogging test. Placed alternately in front of the right and left eye (with best distance correction in place), a +2.00D lens will produce more distance visual annoyance when in front of the dominant eye. An UltraVue P contact lens will then be designed for the dominant eye, while a complimentary UltraVue C contact lens is designed for the non-dominant eye.

* Base curve selection -- Base curve is based on the average keratometry recording. Please note that the average reading is somewhat different than is usually employed in soft contact lens fitting. Using this base curve selection philosophy can result in choosing a steep base curve sooner than when traditional methods are used.

* Distance and add power determination -- The distance refractive powers of both the UltraVue P and UltraVue C lenses are calculated from a valid refractive spherical equivalent, which can be corrected for vertex if necessary.

After substantial clinical review, we have found that the add power for both designs should be adjusted to enhance near visual acuity. Utilizing the refractive add, practitioners should round the add up to the nearest 0.50D and add +0.50D. As an example:

Refractive add: +1.25D +2.00D +2.25D

Round up to: +1.50D +2.00D +2.50D

Final UltraVue add: +2.00D +2.50D +3.00D

* Central zone diameter determination -- During a test launch in the United States, we attempted to match central zone diameters to pupillary zone diameters measured in normal room lighting. Upon review, we found very little correlation between practitioner-measured pupillary diameters and final central zone sizes. Therefore, unless pupillary diameters are unusually small (less than 3.0mm) or large (greater than 5.0mm) we now recommend starting with the central zone diameters illustrated in Figure 4.

Initially, a 2.6mm central zone diameter should be selected for all UltraVue P minus lenses, while plus lenses should be designed with the smallest available diameter of 1.7mm. Our data reveals that the above recommendations yield substantially fewer exchanges than did the original recommendations.

* Initial dispensing -- At the dispensing visit, patients should be allowed to wear their new lenses for approximately 15-20 minutes prior to review. After stabilization, practitioners should assess lenses for comfort, centration, movement and visual acuity.

Contact lens discomfort that can not be resolved with irrigation or removal and cleaning, is most likely related to a flat lens fit, which often exhibits contact lens decentration and excessive movement. Due to the very specific nature of the UltraVue lens' refractive zones, lens centration is vital to clinical success of this technology. In addition, post-blink movement of greater than 0.5mm will result in variable and fluctuating visual acuity.

Some adaptation is to be expected with the UltraVue system as the principles of simultaneous vision and monovision, although vastly enhanced, are being utilized. Most patients note that any early loss in contrast tends to resolve within a few days.

The UltraVue lenses are manufactured from the Benz 45G material. This material has exhibited low on-eye dehydration and minimal coating. Still, owing to its durable nature, we recommend a lens care routine consisting of a separate surfactant cleaner and weekly enzymatic cleaning.

* Follow-up evaluations -- Contact lens wearers should undergo a follow-up evaluation based upon their practitioner's recommendations. The lens dynamic fitting variables of comfort, centration, movement and visual acuity should be addressed. If the appropriate parameters have been employed, we expect contact lens wearers to note the previously mentioned 20/20 - 20/40 visual acuities with improved contrast from the dispensing visit.

* Problem-solving -- Problem-solving to enhance visual performance is vital to the overall performance and success of the UltraVue lens system. As a reminder, UltraVue lenses work together as a system, but practitioners need to measure monocular visual acuities at distance and near to truly understand how the system is functioning.

You should expect, as previously discussed, 20/20 distance and 20/40 near vision in one eye with 20/40 distance and 20/20 near vision in the contralateral eye. When these expected acuities are not found, you should overrefract at the distance with the eye exhibiting reduced vision. After establishing and holding the overrefraction in place, you should then check the vision at the opposite viewing distance.

For example: imagine that a contact lens wearer is complaining of blurred near vision and the UltraVue C lens is offering the intended 20/40 distance and 20/20 near vision. The UltraVue P lens, however provides 20/20 distance and 20/80 near vision. The UltraVue P lens is the cause of the less-than-expected blurred near vision. To determine appropriate parameter adjustments, practitioners should attempt to improve the near vision with an overrefraction at near. Once established, distance vision should then be re-tested.

Armed with monocular visual acuities and overrefractive results, practitioners can quickly understand where the system is breaking down and how to improve visual results. To fully understand and apply the UltraVue technology, it should be considered a system of unique and complimentary reverse geometry hydrogel contact lenses. The lenses allow for the simultaneous correction of myopia, hyperopia and presbyopia in an easy-to-understand, fit and modify system that remains consistent throughout all stages of presbyopia.

Furthermore, the UltraVue contact lens system offers a vast array of parameters to allow for fitting a wide range of refractive errors and effective problem-solving, and it's manufactured from a high-tech hydrogel polymer capable of servicing the demanding needs of presbyopic eyes.

By recognizing the rapidly expanding and vastly under-served presbyopic market, the UltraVue system affords practitioners a newfound opportunity to differentiate themselves as specialty eyecare providers.

FIG.1: The UltraVue system's two-lens design.	FIG. 2: The UltraVue P contact lens design.
FIG. 3: The UltraVue C contact lens design.	FIG. 4: The parameters of the UltraVue Lens system.

Dr. Bridgewater is the founder of Acuity One, LLC, and maintains a private practice concentrating on unique contact lens applications in Phoenix, Ariz.

Dr. Farkas is a partner in a large contact lens specialty practice in New York City, NY. He is a diplomate and former chairperson of the AAO's Cornea and Contact Lens Section.

Dr. Toscano is in a partnership practice in Virginia Beach, Virg., where he specializes in contact lenses and primary care. He is a veteran of over forty-five major clinical
research projects.