Article

GP INSIGHTS

ASPHERIC MULTIFOCAL GPs: FRONT, BACK, OR BOTH?

When patients need multifocal (MF) contact lenses, what are your options? Although soft MF lenses have improved greatly, many patients’ needs are still best met with GP corneal lenses. There are two main types of MF GPs—the aspheric simultaneous-viewing design and the translating design that mimics a segmented bifocal or trifocal. Here is a more in-depth look into the various aspheric designs, with an emphasis on candidate selection and fitting philosophy.

Candidate Selection

The most significant benefit of aspheric MF lenses is simultaneous viewing, which does not require patients to look down to benefit from the near add. Patients who look mostly in the primary gaze, such as those who work at desktop computers, are ideal candidates. These lenses maximize distance and intermediate vision, making them the lens of choice for on-the-go lifestyles. Patients who have loose or low-riding lower eyelids that cannot push a translating lens up during downgaze are also best served by this design.

Lens Designs

The aspheric MF GPs can generally be divided into three designs.

Figure 1. A well-fit back-surface aspheric multifocal showing a slightly steep pattern.

  1. Back-Surface Aspheric With the asphericity on the back surface providing the add power, the fitting strategy has to change a bit. These lenses are typically fit 1.0D to 1.5D steeper than K and typically have less lid attachment (Figure 1). If they are fit too steep, some patients may notice discomfort and may complain that the lens feels “too tight.” These lenses can also cause corneal molding with long-term wear. These were some of the earliest aspheric designs. In addition, these lenses are easily fit based on fitting guides.
  2. Front-Surface Aspheric These lenses are optimal for experienced GP wearers. By keeping their habitual back-surface parameters, few fitting adjustments need to be made, thereby minimizing refits. The spherical base curve and alignment fitting reduce back-surface molding and topography changes. They also allow for toric base curves, if necessary.
  3. Bi-aspheric (Dual-Surface) These lenses have both front- and back-surface aspheric optics. This allows for higher add powers for patients who have more significant near demands.

Final Thoughts

The best way to succeed with MF GP lenses is to closely follow the fitting guides and to work with the lab consultants to adjust lens parameters as needed. Like all GP lenses, tailoring the lens parameters to a patient’s unique situation is possible and makes these lenses a valuable part of your specialty lens tool kit. CLS