A multifocal contact lens has multiple prescription strengths within a single lens, helping people with presbyopia to see clearly or slow down the worsening of myopia in children.
Multifocal contact lenses are a specialized type of contact lens that integrates multiple prescription strengths within a single lens. The design of these lenses enables vision correction at various distances, including near, intermediate, and far.
For individuals dealing with presbyopia, age-related farsightedness, multifocal contacts provide the convenience of addressing both reading and other close-up tasks without the necessity of additional glasses.
In addition, multifocal contacts can be beneficial for children dealing with myopia. These lenses may assist in controlling myopia by introducing peripheral myopic defocus.
A Concise History of Contact Lenses
The Early Concepts:Â The roots of contact lenses trace back to Leonardo da Vinci, who, in 1508, conceptualized an early version of a device aimed at correcting poor eyesight. This laid the foundation for the evolution of contact lenses as we recognize them today.
The First Prototype: In 1801, John Young crafted a glass contact lens prototype. However, these early lenses presented challengesâbeing heavy and covering the entire eye. Moreover, the impermeability of glass to oxygen made them uncomfortable and potentially unsafe.
From Glass to Plastic and Hydrogel: Over time, advancements addressed the limitations of glass lenses. The introduction of plastic and later, hydrogel, marked significant milestones. These materials provided lighter, more comfortable lenses capable of absorbing water and facilitating increased oxygen flow to the eyes.
The Era of Commercial Soft Contact Lenses: In the early 1970s,
Bausch & Lomb introduced the first commercial soft contact lenses made of hydrogel. This breakthrough opened avenues for multifocal and toric lenses, catering to myopic individuals, especially those with presbyopia or astigmatism.
The Advent of Silicone Hydrogel: In the late 1990s and early 2000s, silicone hydrogel emerged as a game-changer. This material quickly became the preferred choice for crafting contact lenses due to its exceptional properties. Silicone hydrogel lenses allow significantly more oxygen to reach the eyes, promoting better eye health. Furthermore, they absorb more water than hydrogel counterparts, enhancing flexibility and fit.Â
Silicone hydrogel, especially in the form of daily contact lenses, gained widespread popularity for its ease of use and hygiene. These features have also contributed to the suitability of soft contact lenses for children, particularly in the context of myopia control.
How do multifocal contact lenses work for presbyopia?
Similar to multifocal eyeglass lenses, multifocal contacts consist of different zones that cater to various focal points, including âplus powerâ zone(s) for close-up tasks. These zones are strategically placed to accommodate the natural function of your pupils; when you gaze at distant objects, the pupils of your eyes dilate slightly, and they constrict when you focus on something up close or read.
The visual zones within multifocal contacts are designed to align with these subtle changes in pupil diameter. This alignment enables you to see clearly, allowing your eyes to naturally focus on objects whether they are near or far.
How do multifocal contact lenses work for myopia control in children?
To understand how multifocal contacts function in controlling myopia progression in children, it's crucial to grasp the concept of peripheral hyperopic defocus. This phenomenon occurs when light focuses behind the retina in the outer areas of the visual field. Research indicates that peripheral hyperopic defocus contributes to the rapid progression of myopia in children by sending signals to the brain that accelerate the growth of their eyes.
Researchers suggest that optical lenses can play a pivotal role in addressing this issue. Specially designed lenses can either eliminate peripheral hyperopic defocus or induce peripheral myopic defocus, slowing down the progression of myopia
Among the various optical lens options, contact lenses stand out as an optimal method due to their ability to stay relatively centered with eye movements, ensuring consistent correction across the entire visual field.Â
Additionally, the design of multifocal contact lenses provides clear central vision while incorporating "plus power" zone(s) outside the central distance zone, inducing myopic defocus for effective myopia control. This makes multifocal contact lenses a promising approach to managing myopia progression in children.
What are the different types of multifocal contact lenses?
Multifocal contact lenses come in various types. The three main types are concentric, aspheric, and segmented bifocal contact lenses. Additionally, some lenses combine features from concentric and aspheric multifocal, offering the advantages of both designs.
Concentric Multifocal Contact Lenses: These lenses showcase concentric circles on the lens, resembling a bullseye. Each circle alternates between near and distance vision zones. The center bullseye represents either a near or distance zone, with subsequent rings alternating strengths. For presbyopia, Acuvue from Johnson and Johnson utilizes this design, while for myopia control, the MiSight 1 Day.
Aspheric Multifocal Contact Lenses: Similar to progressive lenses, these contacts possess a central prescription strength with a gradual transition in power across the lens. Brands like Dailies Total 1 Multifocal employ this design for individuals with presbyopia. For myopia control, brands such as NaturalVue Multifocal 1 Day or Biofinity Multifocal incorporate this progressive power transition.
Segmented Bifocal Contact Lenses: Also known as translating multifocal lenses, these rigid gas-permeable lenses mimic bifocal glasses. The near zone is positioned at the bottom, and the distance zone is in the top half of the lens. The lower edge is flattened to enhance stability. While listed, this design is less common and is typically custom-made.
Can multifocal contact lenses be used for treating astigmatism?
Toric contact lenses are specially designed contact lenses to address astigmatism, and some multifocal contact lenses are available in toric versions. What distinguishes these lenses is their unique shape, incorporating different focusing powers both vertically and horizontally. This design corrects astigmatism, offering clearer vision for individuals managing multiple refractive errors simultaneously, such as myopia, presbyopia, and astigmatism.
Due to the intricacies of toric lens prescriptions, it is crucial for these contacts to stay in place to correct vision accurately. Consequently, toric contact lenses are designed to ensure stability in the eye; the thickness of the lenses may vary in multiple zones, and in some instances, the bottom might be truncated or weighted.
For whom are multifocal lenses most appropriate?
Presbyopia: There are various options available for treating presbyopia, ranging from optical lenses to surgery. Multifocal contact lenses are suitable for individuals with presbyopia and myopia who seek clear vision without the need for glasses. They are also appropriate alternatives for those already using monovision contact lensesâlenses with different prescriptions for near and far vision in each eye.
Children with myopia: Multifocal/Dual-focus contact lenses may be more suitable for children who are old enough to maintain good hygiene practices, as cleanliness is crucial when using contact lenses. Additionally, children, who enjoy non-water related sports or activities where glasses may not be practical, may find multifocal lenses their preferred treatment.
In the United States, MiSight is the only multifocal contact lens approved by the FDA, with extensive published data supporting its effectiveness. Other multifocal contact lenses, such as NaturalVue MF, Biofinity MF, and Proclear MF, are sometimes used off-label by eye doctors in the USA.Â
Key Takeaways
Multifocal contact lenses, designed with multiple prescription strengths, work by aligning with pupil changes, delivering clear vision for various distances for those with presbyopia or inducing peripheral myopic defocus to mitigate myopia progression. The three primary types include concentric, aspheric, and segmented bifocal designs. Toric multifocal lenses are specifically suitable for individuals with astigmatism. As contact lens technology continues to advance, we can anticipate further innovations that enhance comfort, address specific visual needs, and contribute to the overall well-being of individuals seeking better eye health.
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