Varifocal contact lenses, often called multifocal lenses, are a specialized method for vision correction. They are designed to address presbyopia, the gradual loss of the eye’s ability to focus on close objects, which typically begins around age 40. Varifocal contacts provide a seamless visual experience, eliminating the need for separate reading glasses or the visible lines found in traditional bifocal spectacles. They incorporate multiple optical powers within a single lens, offering clear sight for near, intermediate, and far distances.
The Optical Principle of Varifocal Lenses
Varifocal contact lenses work by leveraging two primary optical strategies to project multiple focal points onto the retina simultaneously or sequentially. The most common approach is simultaneous vision. In this design, the lens contains distinct zones for distance, intermediate, and near vision positioned in front of the pupil at all times.
These lenses typically use concentric ring designs, where alternating power zones are arranged around the center of the lens, much like a target. Other designs employ aspheric surfaces, where the lens power gradually changes from the center to the edge, creating a smooth transition between prescriptions. The brain learns to subconsciously select the appropriate clear image for the task at hand and ignores the slightly blurred images from other focal points. This neural adaptation is necessary because the lens compensates for the eye’s diminished natural focusing ability, known as accommodation.
A less common design, usually found in Rigid Gas Permeable (RGP) lenses, is the alternating or translating vision principle. These lenses have distinct, separate segments for distance and near correction, often with the near segment located in the lower half. When the wearer looks down to read, the lens physically shifts or “translates” upward on the eye, bringing the near power zone into alignment with the pupil. This mechanical shift provides a more defined separation of powers but requires the lens to be stable and correctly oriented on the eye.
Available Lens Types and Wear Schedules
Varifocal contact lenses are available across a wide spectrum of materials and replacement schedules to suit different patient needs and lifestyles. The two main material categories are soft lenses (including hydrogel and highly breathable silicone hydrogel) and Rigid Gas Permeable (RGP) lenses. Soft varifocal lenses are generally easier to adapt to and are a popular choice due to their immediate comfort and flexibility.
Soft lenses offer the greatest variety of wear schedules, which determines how often they must be replaced.
- Daily disposable lenses are worn once and then discarded, providing the highest level of convenience and hygiene.
- Bi-weekly lenses are replaced every two weeks.
- Monthly disposable lenses are cleaned and stored nightly and replaced once a month.
- RGP lenses require a longer adaptation period and are typically worn for extended periods with a more rigorous cleaning regimen.
What to Expect During the Fitting Process
Obtaining varifocal contact lenses requires a specialized eye examination and a precise fitting process overseen by an optometrist. The eye care professional must first determine the full range of your vision needs, including the specific near power addition required to compensate for your presbyopia. The fitting is more complex than for single-vision lenses because the doctor must consider not only your prescription but also factors like your pupil size and visual demands.
A trial period is almost always necessary because successful wear depends heavily on how your brain adapts to the new visual input. The optometrist will provide trial lenses and may need to fine-tune the prescription based on your real-world feedback, sometimes adjusting the power in one eye for better overall balance.
It is normal to experience minor visual disturbances, such as slight ghosting or reduced contrast, especially in low-light conditions, during the initial weeks of wear. Consistent wear is important, as the brain’s adaptation to the simultaneous focus of multiple prescriptions can take one to two weeks.