First Impressions of a New Disposable Bifocal

This clinical investigator's observations about the new Acuvue Bifocal lens could help you maximize the utility of this new presbyopic tool.

BY PETER BERGENSKE, OD, FAAO

What if a successful lens design were combined with the convenience of lens disposability, the profitability of a specialty fit and the patient's natural acceptance of a bifocal? With the introduction of the Acuvue Bifocal contact lens from Vistakon, Inc., such a combination exists.

The Acuvue disposable bifocal design is similar to other bifocal contact lenses. It has a center distance zone surrounded by a ring of near, surrounded by another ring of distance, allowing for acceptable distance vision under low illumination. Key to the success of the design of the Acuvue Bifocal is that, although available in only one base curve (8.50mm) and one diameter (14.2mm), it is definitely not a "one size fits all" lens. Each of the distance powers (-6.00D to +4.00D) is available in add powers of +1.00D, +1.50D, +2.00D and +2.50D. This provides the fitter with the flexibility to modify the optimum range of vision, and allows him to use a modified monovision approach by fitting different add powers on the dominant and nondominant eye. Initial lens choice is simple -- select the sphere and add power based on refraction data, and allow the lenses to settle for up to 10 minutes.

Like its single-vision predecessor, the Acuvue Bifocal has a visibility tint, a UV-blocking agent and is approved for two-week daily wear and one-week extended wear. It is made of the same etafilcon A, 58 percent water content material that has been used in Acuvue, Surevue and 1-Day Acuvue products. The lens is thin (similar to standard Acuvue lenses), and the comfort is excellent due to the edge design, but this also makes it difficult to tell whether the lens is inverted or not. Although inside-out lenses are sometimes comfortable, the vision is poor. As a clinical investigator for the lens, I found that I could detect an inverted lens at the slit lamp by looking for the tell-edge bevel that is visible only when the lens is inverted. The product currently on the market now contains a "1-2-3" inversion mark that's somewhat similar to other Acuvue lenses.

The Lens in Action

After allowing the initial lenses to settle and assuring that they are inserted properly, assess distance and near acuity binocularly. It's common for near vision to be pretty good, even though distance vision may be off by a line or two. Similar to prescribing monovision, don't hesitate to make small changes in the lens power because they can sometimes make significant differences in patient acceptance. Large changes to the initial correction are rarely helpful. It's common to need to change one or both lenses one or more times to reach a satisfactory visual result, but usually theses changes are only �0.25D on the distance power and up to one add power different than the initial selection. While performing the refraction prior to fitting, take the extra time to assess relative dominance (see sidebar below). This may prove useful, should you find the need to shift to a modified monovision approach, which may be indicated if distance vision is unacceptable with full near correction. Try the full add power on the dominant eye and the next lower power on the non dominant eye. If distance vision is still unacceptable, try a single vision lens on the nondominant eye.

Success Rates

As expected, success with the Acuvue Bifocal is best in the lower add range, with reports as high as 88 percent among emerging presbyopes. Success rates drop as the add power increases, but even among presbyopes who call for 2.50D add, success has been in the 50 percent range. Screening for patient expectations and visual demands is always important for achieving a reasonable success rate.

Trying to refit patients who are already pleased with monovision is often unproductive, so I suggest maintaining patients' existing contact lens option unless they request a change. For monovision wearers who complain of too much interference with their distance vision, I've had success fitting the Acuvue Bifocal on the near eye only. The near vision will often be just about as good as with full monovision, and the distance is almost always better.

More Choices for Presbyopes

I have always thought of monovision as a highly acceptable method of satisfying presbyopic patients. However, I have noted a strong trend in my own practice to prescribe multifocal rigid lenses. Multifocal RGPs are more profitable to the practice, more logical from the patient's perspective and in many cases, easier to fit than monovision. Additionally, there have been few effective, profitable soft lens multifocal options.

Still, monovision has continued to dominate presbyopic contact lens care, particularly due to the relative simplicity that disposable trial lenses deliver. The ease of sampling monovision and the availability of immediate power change while the patient is still in the office has greatly reduced the down time in the soft lens monovision process.

The Acuvue Bifocal is a significant addition to our choices for satisfying the presbyopic contact lens patient. It has the potential to become your first choice

lens for soft contact lens wearers, given the appropriate prescription range. It does require additional time and patience in order to achieve successful fits, but keep in mind -- this justifies a higher fee. Combining disposable lens fitting convenience and a variety of add powers is, at least to date, the best system for fitting a soft multifocal lens. CLS