Astigmatic presbyopia patients can officially celebrate the ability to choose different soft multifocal toric contact lenses that offer comfortable, clear, and seamless vision at distance and near. Gone are the days of eye care professionals offering the limited choices of monovision soft contact lenses for astigmatism with readers over top or masking astigmatism with soft multifocals.
Before we take a closer look at the best contact lenses and what soft multifocal torics recently became available on the market, let’s first review the original soft multifocal toric contact lens.
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Proclear Toric Multifocals
CooperVision introduced Proclear multifocal torics, the first monthly soft multifocal toric contact lens in 2007. The hydrogel lens material uses a cast molded back surface toric with an inverse prism ballast at 3 and 9 o’clock and contains phosphorylcholine molecules, which bind with water molecules in natural tears to create a water shield around the lens. Proclear is the only multifocal lens cleared by the FDA for the claim that it may provide improved comfort for contact lens wearers who experience mild discomfort or symptoms relating to dryness during lens wear.1
Figure 1. Balanced Progressive Technology by CooperVision
Featuring a front surface Balanced Progressive Technology, Proclear multifocal toric lenses combine optics of a spherical center, aspheric surround, and unique zone sizes to produce a "D" lens for the dominant eye and an "N" lens for the non-dominant eye. These two lens designs work together to maximize binocular visual acuity at all distances (Figure 1). Balanced Progressive Technology allows for independent adjustment of either the distance sphere power or ADD power of a maximum of +/- 0.50. This means the ADD can be changed up to +/- 0.50 without affecting the distance sphere power and vice versa on the same eye. Monocular verification of visual acuities must be assessed if a problem exists with binocular visual acuities at distance or at near. After the initial fit, binocular vision is first assessed. If vision is not to visual acuity expectations as listed on the fitting guide, performing monocular visual acuities next is an absolute must. A common misconception is that if there is a problem with distance, it is in the “D” lens. Since both lenses incorporate distance, intermediate, and near vision, often the problem with the distance vision will be in the “N” lens.2
Even though Proclear multifocal torics offer a wide range of parameters to fit virtually any astigmatic presbyope (Figure 2), overall comfort and fit of the lens after hours of wear may become problematic due to the hydrogel lens material accumulating high levels of proteins over time, and a low Dk/t value of approximately 38 that is not ideal for optimal corneal health. The lens does not offer UV protection and has a very low modulus of 0.4 MPa that can increase handling difficulties during insertion and removal because the lens is too soft and flexible.
Figure 2. Proclear Multifocal Toric product details
The latest brands of soft monthly multifocal toric contact lenses that recently became available on the market have been clinically shown to offer clear vision at all distances while simultaneously providing optimal comfort and fit.
Biofinity Toric Multifocals
CooperVision’s Biofinity toric multifocal contact lenses offer front surface Balanced Progressive Technology, which was previously discussed with the Proclear multifocal toric contact lenses making the optics and initial fitting process of both lenses comparable. The Biofinity toric multifocal combines proven lens design technologies such as Aquarform and Optimized Toric Lens Geometry to keep vision crisp and clear at all distances. Like all Biofinity family lenses, UV protection is not offered but the lenses do provide 100% of the oxygen needed to maintain optimal corneal health, and provide eyes the natural wettability and comfort needed to sustain long-time wear.
Figure 3. Optimized Toric Lens Geometry by CooperVision
Aquaform is a group of technologies developed by CooperVision and originally introduced with the Biofinity lenses in 2007. Aquaform Technology is comprised of first, a silicone hydrogel lens material that supports a high level of oxygen transmissibility through the lens to the cornea. This lens material comes with a value of up to 160 Dk/t. Second, the modulus provides the perfect degree of lens flexibility of 0.75 MPa which makes the lens soft and comfortable though rigid enough for proper handling. Third, the lens is made up of a non-coated molecular structure that involves silicone macromers that locks water molecules into the lens, keeping the lens and eyes moist even after many days into the wearing cycle. And last but not least an optimized rounded-edge design that reduces conjunctival interaction keeping the lens from rubbing too much on the inside of the eyelid providing an increased level of comfort.3
Figure 4. Biofinity Toric Multifocal product details
Too much lens movement with toric lenses can diminish the quality of vision for astigmatic patients. Optimized Toric Lens Geometry by CooperVision provide astigmatic patients with the visual acuity and stability they need. The uniform horizontal ISO lens thickness improves centration and stability by reducing lens rotation. The wide ballast band increases the area devoted to stability and a comfortable fit. The smooth, continuous lens surface maximizes comfort during eyelid interaction and the larger toric optic zone provides clear visual acuity over an extensive range of powers. And the unique back surface curvature reduces movement on the eye, creating a more stable, dependable fit (Figure 3).4 Similar to Proclear multifocal torics, Biofinity toric multifocals also offers a wide range of parameters to fit many astigmatic presbyopes (Figure 4).
ULTRA Multifocals for Astigmatism
Bausch + Lomb’s Ultra Multifocals for Astigmatism features MoistureSeal technology, which helps to maintain 95% of lens moisture for 16 hours through a unique two-phase polymerization process. MoistureSeal technology is created through a chamber that uses radiant energy to polymerize the lens material in two distinct phases. The first phase creates a matrix that has a combination of long- and short-chain silicone molecules. The longer chains are responsible for the ideal modulus of 0.7 MPa, while the short chains increase the Dk/t to approximately of 115. The second phase of the polymerization process grows a water-loving polymer, polyvinylpyrrolidone (PVP) around the meshwork of long- and short-chain silicone molecules. As a result, MoistureSeal technology reportedly has four times more PVP compared to other silicone hydrogels. The Ultra lens achieves a high level of both overall and end-of-day comfort while exhibiting a very low level of deposition at the end of the monthly wearing cycle.5
The Ultra Multifocals for Astigmatism provides the 3-Zone Progressive Design, which is distinguished by large areas of consistent focusing power in the near, intermediate and distant zones. In other words, with the consistency of power, a patient's retina receives a properly focused image, one that remains consistent within each area of the near, intermediate, and distant zones. A dedicated wide area of consistent power within each zone provides the retina with a clear image at these key distances (Figure 5).
Figure 5. Bausch + Lomb’s 3-Zone Progressive Design
Bausch + Lomb’s OpticAlign lens design offers stability with the downward force of each blink and limits lens rotation. The lens is thinnest beneath the upper eyelid and ballasting offered in the lower hemisphere provides a stable fit and consistently clear vision. Eye care professionals report rotation of 5 degrees or less for 94% of patients when fitting Bausch + Lomb Ultra for Astigmatism. Spherical aberration is also controlled in both axes to help reduce halos and glare in low light conditions, like night driving.5