Bifocal contact lenses are available, though eye care professionals typically refer to them as “multifocal contact lenses.” This specialized technology corrects presbyopia, a common age-related condition that causes difficulty focusing on near objects, usually after age 40. Presbyopia occurs because the eye’s natural lens becomes less flexible, compromising its ability to focus light clearly for near tasks. Multifocal lenses incorporate different prescriptive powers into a single lens, aiming to restore both distance and near vision without the need for reading glasses.
Understanding the Technology: Providing Multiple Focal Points
The central optical challenge addressed by multifocal lenses is delivering clear vision for objects at various distances simultaneously. Unlike traditional single-vision lenses, which correct for only one distance, multifocal lenses contain distinct zones of power for far, intermediate, and near vision. The most common approach is the simultaneous vision design, where the wearer looks through all prescriptions at the same time. This means light rays from objects both far and near enter the eye concurrently, creating two overlapping, slightly blurred images on the retina.
The success of simultaneous vision depends on the brain’s ability to selectively interpret the visual information it receives. The brain automatically learns to suppress the blurred image and favor the clearer one that corresponds to the object of focus. As the pupil naturally changes size in response to light levels and viewing distance, the eye is directed toward the most appropriate power zone on the lens. The optical design effectively creates an extended depth of focus, allowing the wearer to see clearly over a continuous range of distances.
Specific Designs: Simultaneous vs. Segmented Lenses
Multifocal contact lenses are categorized into two primary design groups. The most prevalent type is the simultaneous vision design, which includes two main styles: concentric and aspheric. Concentric designs feature a central zone for distance or near vision, surrounded by alternating, ring-like zones of the other power, resembling a bull’s-eye pattern. Aspheric designs utilize a gradual, blended change in power across the lens surface, similar to a progressive eyeglass lens, ensuring no distinct lines are visible.
Both concentric and aspheric lenses are typically made from soft materials and remain centered on the cornea, moving with the eye. The multiple prescriptions are always in front of the pupil, relying entirely on the brain’s filtering process for clarity. A less common alternative is the segmented design, often referred to as translating or alternating lenses. These lenses, usually made of rigid gas permeable (RGP) material, are designed like traditional bifocal glasses, featuring a clear separation line between distance correction (upper section) and near correction (bottom).
Segmented lenses are weighted at the bottom to maintain a stable orientation on the eye. When the wearer looks down to read, the lower eyelid catches the bottom edge of the lens, physically pushing it upward. This translation causes the pupil to align with the lower, near-vision segment. This mechanical action means the eye looks through only one power at a time, which can provide sharper vision compared to the simultaneous blur inherent in soft lens designs.
The Patient Experience: Fitting, Adaptation, and Cost
Fitting Process
Obtaining a successful prescription for multifocal contact lenses requires a specialized fitting process performed by an eye care professional. Due to the complexity of the optics and the different ways they interact with the visual system, a degree of trial and error is necessary. The fitting process usually involves trying several different lens designs or power combinations, and it may take an average of 1.5 to 3 trial lenses per eye to achieve a satisfactory result. This initial fitting appointment often takes longer and may involve a higher fee than a standard contact lens fitting.
Adaptation Period
Once the initial lenses are selected, a necessary period of adaptation begins, which is a process of “cortical adaptation” where the brain learns to manage the overlapping images. Wearers are advised that it may take several weeks for their vision to fully settle and for them to become comfortable with the lenses. During this period, common side effects may be experienced, such as reduced contrast sensitivity, especially in low light, or visual disturbances like ghosting and glare around bright sources at night. Patients with a lower magnitude of presbyopia, or “add power,” tend to adapt more quickly to the simultaneous vision designs.
Cost and Availability
Multifocal contact lenses are more expensive than single-vision contact lenses because of the advanced technology and the increased time and expertise required for the fitting. They are available in both reusable and daily disposable formats, with daily disposables typically correlating with a higher annual cost. Achieving a successful fit is a collaborative effort, requiring patience from the wearer and ongoing consultation with the eye care provider to fine-tune the final prescription.