Yes, contact lenses can effectively correct the difficulty in focusing on near objects that often occurs with age. This condition, known as presbyopia, involves the gradual loss of the eye’s ability to change focus, making reading materials and small print appear blurry unless held at a distance. Modern contact lens technology offers practical alternatives to reading glasses, allowing individuals to maintain clear vision across a range of distances. The two primary strategies used by eye care professionals to achieve this correction are monovision and multifocal lenses.
Correcting Vision with Monovision
Monovision is a straightforward contact lens strategy that uses two single-vision lenses, dedicating each eye to a different task. The dominant eye is typically fitted with a lens that corrects for distance vision, while the non-dominant eye receives a lens optimized for near or reading vision. This system creates a deliberate difference in focus between the two eyes, a state known as anisometropia.
The success of monovision relies on neural adaptation, where the brain learns to automatically select the clearer image for the task at hand. When looking far away, the brain prioritizes the distance-corrected eye, and when reading, it uses the near-corrected eye. This brain-mediated filtering allows the wearer to function without consciously choosing which eye to use.
A potential trade-off is a reduction in stereopsis, the ability to perceive depth accurately, because the eyes are not focusing on the same point. This can affect activities demanding precise depth judgment, especially in low-light conditions. A variation called “modified monovision” uses a distance-corrected lens in the dominant eye and a multifocal lens in the non-dominant eye to provide better intermediate vision.
The Design of Multifocal Lenses
Multifocal contact lenses incorporate multiple optical powers—for distance, intermediate, and near vision—all within a single lens. This allows both eyes to contribute to vision at all distances using the principle of simultaneous vision. The eye looks through all prescriptions at once, and the brain determines which image is in focus, helping maintain binocular vision and better depth perception than monovision.
The most common soft multifocal lens designs are either concentric or aspheric. Concentric designs feature a bulls-eye pattern with alternating rings of near and distance power. Aspheric designs function more like progressive eyeglass lenses, where the power gradually changes across the lens surface, blending the prescriptions. Both simultaneous vision designs rely on the brain selecting the appropriate focus for the object being viewed.
A less common design, typically found in rigid gas-permeable lenses, is the translating or alternating vision lens. This design is segmented, much like traditional bifocal glasses, with distinct distance and near zones. The lens is weighted and shaped to move upward when the wearer looks down to read, positioning the near-vision segment over the pupil. A common optical compromise with multifocal lenses is a reduction in image crispness or the possibility of minor glare or ghosting.
Adaptation and Professional Fitting
Achieving success with reading contact lenses depends on a careful, professional fitting process that considers the patient’s lifestyle. The eye care professional must first determine the individual’s ocular dominance, which is the eye the brain naturally prefers for visual tasks, especially when fitting monovision. They also consider factors like the patient’s pupil size, which affects how light passes through the multiple zones of a multifocal lens.
A period of adjustment is necessary for the brain to acclimate to the new visual input, whether it is the split focus of monovision or the multiple simultaneous images from multifocal lenses. This adaptation can take anywhere from a few days up to two weeks, and patience is important during this time. Initial side effects may include temporary difficulty judging distances, dizziness, or mild blurriness, especially when shifting focus.
To ensure the best outcome, eye care professionals use trial lenses before finalizing a prescription. This process allows the patient to experience the specific visual compromises and benefits of the chosen lens design in their daily life. The successful outcome is a balance between the patient’s visual needs and their ability to adapt to this new way of seeing.