CONTACT LENS DESIGN & MATERIALS
WHICH MULTIFOCAL DESIGN IS BEST FOR YOUR PATIENTS?
GREGORY J. NIXON, OD
When considering the options for presbyopic contact lens wearers, it is my experience that multifocal lenses provide more natural vision at all distances compared to monovision.
This is supported by two studies (Richdale et al, 2006; Woods et al, 2009) in which early presbyopes chose multifocals over monovision as their preferred mode of correction. So, the next question is: Which multifocal lens design is the best? We all know that there isn’t a single lens design that can meet the visual needs of all patients. However, there are some common trends that make certain patient scenarios more successful with certain designs.
The most common cause of multifocal failure is lack of achieving an adequate balance of distance and near clarity. Specifically, inducing distance blur is often a deal breaker when refitting a new presbyope from a single-vision distance lens into a multifocal. Therefore, emerging presbyopes are considered good candidates for a center-distance lens in each eye.
This will limit the amount of disruption to the distance vision by having the portion of the lens over the visual axis containing the distance Rx blending into the bifocal power toward the periphery. This type of fitting approach may also be appropriate for patients who have substantial work-related distance visual tasks, such as driving.
The majority of the current soft multifocal contact lenses utilize a center-near design for each eye. The patient’s reading prescription is aligned to the visual axis, blending into the distance power toward the periphery.
Obviously, the great advantage of these lenses is improved near acuity. These lenses have vast utility for most office workers who have the majority of their work-related visual tasks at close distances on their desk or computer screen.
To achieve an adequate balance of distance and near clarity, it is sometimes necessary to use different add powers in each eye. Specifically, you should use a lower add in the dominant eye and a higher add in the nondominant eye.
Center-Distance and Center-Near Lenses
Certain brands of lenses are designed to have a center-distance lens on the dominant eye and a center-near lens on the nondominant eye. I consider this a good option when refitting a monovision patient into multifocal lenses.
First, these patients are used to their eyes not having equal acuity. But, most importantly, the add powers in each eye provide improved vision at intermediate distances compared to monovision.
Other patients who often do well with this fitting arrangement are nurses or other workers who are in constant motion and who have varied distance, intermediate, and near tasks throughout the day.
Rest assured, the scenarios mentioned above are not the only times for which each of these multifocal designs is effective. The most important takeaway is that practitioners have an array of multifocal lenses in their arsenal to meet their patients’ needs. So, be sure to recommend multifocal lenses to your patients to increase their awareness of the advances in technology available to help them keep pace with their busy lives. CLS
For references, please visit www.clspectrum.com/references and click on document #253.
Dr. Nixon is the associate dean for Clinical Services and professor of clinical optometry at The Ohio State University College of Optometry. He is also in a group private practice in Westerville, Ohio. You can reach him at email@example.com.