Bifocal & Multifocal Contact Lenses
Presbyopia, a common age-related condition, typically affects individuals over 40 years old. It results in difficulty seeing objects up close due to the natural lens of the eye losing its ability to focus effectively on nearby targets.
Presbyopia and Multifocal Lenses
Presbyopia is a common age-related condition that affects many individuals aged 40 and older. It often requires the use of reading glasses to see objects up close clearly. However, for those who prefer an alternative to reading glasses, bifocal and multifocal contact lenses are available in both soft and Rigid Gas Permeable (RGP) varieties.
Multifocal contact lenses offer the freedom to see in all directions, including up, down, and to the sides, providing similar vision to glasses. In contrast, individuals wearing progressive lenses in glasses may need to look over their glasses to see objects in the distance or above eye level. This makes multifocal contact lenses a convenient and versatile option for individuals with presbyopia.
The Difference Between Bifocal and Multifocal Lenses
Bifocal lenses are named for their two distinct segments, with one segment for distance vision and the other for near vision. This allows for clear vision adjustment between near and far objects, but there may be a blur in between. On the other hand, multifocal lenses encompass various lens types, including bifocals, trifocals, and progressive lenses, that have multiple vision powers. Unlike bifocals, non-bifocal multifocal lenses provide a range of powers, allowing for seamless focus adjustment from near to far and everything in between.
Multifocal contact lenses are typically designed in one of two ways: simultaneous vision lenses or alternating vision lenses.
Simultaneous vision lenses
Simultaneous vision lenses are the most popular type of multifocal contact lenses, as they present both distance and near vision zones on the lens simultaneously. After a short adjustment period, your eyes learn to utilize the specific segment of the lens required to focus on the desired object, while ignoring the other segment.
There are two designs available:
Concentric ring design: This design consists of a central circular area with one power, surrounded by a ring of the alternate power, resembling a bulls-eye pattern. The power of the rings can be interchanged for near or distance vision. Additional rings can be added for intermediate viewing (around 18-24 inches away) to create a trifocal or multifocal lens. The width of each ring varies depending on the required power, and the edges of the rings can be blended for a smooth transition of focus, similar to progressive eyeglass lenses.
Aspheric design: These multifocal lenses aim to provide a more natural vision experience by blending multiple lens powers across the surface and center of the lens. In this design, both distance and near vision powers are located in the central visual area. Your eyes will adapt to focus on the specific area needed to view the object you are looking at.
Translating or Alternating Vision lenses
These contact lenses, similar to bifocal eyeglass lenses, are divided into distinct areas or zones. Depending on your vision needs, your pupil will naturally move to the desired zone. Typically, the top area of the lens, which you look through when looking straight ahead, is designed for distance vision. On the other hand, the bottom area, which you look through when looking down, is intended for near vision. However, this configuration can be reversed based on individual vision requirements.
To ensure proper positioning and stability within the eye, translating lenses utilize a ballast. The ballast is an area on the lens that is thicker than the rest, or the bottom of the lens may be truncated or flattened to align with the lower lid. It helps keep the lens in place even when the eye moves. Translating lenses are exclusively available in rigid gas permeable lens material.
An Alternative Option to Multifocal Contact Lenses: Monovision
Monovision is an alternative contact lens approach for addressing presbyopia, especially if you find it challenging to adapt to multifocal lenses. With monovision, your distance and near vision are divided between your eyes. Your dominant eye is used for distance vision, while your non-dominant eye is utilized for near vision.
Typically, single vision lenses are used in each eye for monovision. However, in some cases, the dominant eye may have a single vision lens, while a multifocal lens is used in the other eye to enhance intermediate and near vision. This variation is known as modified monovision. To determine the most suitable lens type for each eye and achieve optimal vision, your eye doctor will conduct a test.
If you have presbyopia, contact lenses can be a great option worth considering. Many individuals prefer the appearance and convenience of contact lenses over traditional reading glasses. It’s recommended to consult with your eye doctor to explore the available options that best suit your needs.