Astigmatism and presbyopia are two distinct vision challenges that often occur simultaneously. Astigmatism arises from an irregularly shaped cornea or lens, causing light to focus unevenly and resulting in blurred vision at all distances. Presbyopia is the age-related loss of the eye’s ability to focus on close objects, typically starting around age 40, leading to the need for a bifocal correction.
Toric Multifocal Lenses Are Available
The answer is yes: contact lenses can correct both conditions, and they are known as toric multifocal lenses. For many years, patients requiring both corrections were limited to custom-made lenses or had to compromise their vision. Technology has advanced significantly, and most major manufacturers now offer a variety of options, including monthly and daily disposable toric multifocal lenses. This evolution means patients with astigmatism who develop presbyopia no longer have to choose between clear distance and clear near vision. These lenses combine the rotational stability required for astigmatism correction with the multiple focal zones needed for presbyopia.
How Toric Multifocal Lenses Work
Correcting both conditions within a single, soft contact lens requires a sophisticated dual design. The toric component addresses astigmatism by incorporating a different power in two perpendicular axes to compensate for the irregular eye shape. Since this corrective power must remain precisely aligned with the eye’s axis of astigmatism, the lens utilizes stabilization features like prism ballast or a blink-stabilized design.
This stabilization technology ensures the lens quickly reorients to the correct position after every blink, maintaining the proper axis of cylinder correction. Simultaneously, the multifocal component provides vision correction for multiple distances, often using a concentric ring or blended zone design. This creates a simultaneous vision system, where the lens presents distance, intermediate, and near powers over the pupil area.
A common design, known as Balanced Progressive Technology, uses multiple correction zones tailored to the patient’s prescription. The challenge lies in combining these two mechanisms: a toric lens requires consistent rotational stability, while a multifocal lens demands precise centration relative to the pupil to deliver clear vision.
Factors Influencing Fitting Success
Fitting a toric multifocal lens is more complex and time-intensive than fitting a standard lens. The process requires precise measurements of the astigmatism axis, overall power, and the specific near-vision power, known as the “add.” Eye care professionals must often use diagnostic fitting sets and try multiple trial lenses to find the optimal combination of parameters.
Patients must understand that achieving perfect vision at all distances may involve a trade-off compared to single-vision lenses or glasses. Wearers may experience minor visual phenomena, such as decreased contrast sensitivity, halos around lights, or ghost images, particularly in low-light conditions. Successful adaptation relies heavily on the patient’s motivation and the realistic management of their visual expectations.
Success is also influenced by physical factors, including the quality of the tear film and the anatomy of the eyelids, which interact with the lens’s stabilization features. A fitting is successful when the patient achieves functional vision that meets their daily needs, even if the measured visual acuity is slightly less than with a single-vision correction.
Alternative Vision Correction Options
For individuals who do not achieve satisfactory results with toric multifocal lenses, several other options exist. A common alternative is monovision, where one eye is corrected for distance vision and the other eye is corrected for near vision using single-vision lenses. This approach sacrifices some depth perception but eliminates the simultaneous vision effect.
A variation is modified monovision, which uses a single-vision lens for the dominant distance eye and a multifocal lens for the near eye. Patients may also choose to wear single-vision toric lenses for distance and intermediate tasks, relying on reading glasses for near work. More permanent solutions include surgical procedures, such as Refractive Lens Exchange (RLE), or laser vision correction that creates a multifocal effect on the cornea.