What Are Multifocal Defocus Lenses?

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Introduction

The prevalence of myopia, or nearsightedness, is rising at an alarming rate globally, particularly among children and adolescents. This increasing trend poses significant public health concerns, as high myopia can lead to severe visual impairments and ocular complications later in life. Multifocal defocus lenses have emerged as an innovative solution to slow down the progression of myopia in children. In this article, we will explore the basic principles, key technologies, and clinical benefits of these lenses.

The Basic Principle of Multifocal Defocus Lenses

Multifocal defocus lenses are specially designed optical lenses used to correct myopia while simultaneously creating a defocus effect that slows down the elongation of the eyeball. The primary working principle involves the strategic placement of multiple zones with varying focal lengths on the lens surface. These zones include clear vision areas for distance viewing and defocus areas that project light in a way that creates a controlled blur on the peripheral retina, which helps to halt the progression of myopia.

Key Technologies and Brands

HOYA® MiYOSMART® Lenses

  • D.I.M.S.® Technology (Defocus Incorporated Multiple Segments)
  • Technology Overview: D.I.M.S technology incorporates multiple segments of defocus and clear vision zones that are alternately distributed across the lens surface.
  • Advantages: This design ensures that the peripheral retina receives a consistent defocus signal, thereby preventing the eye from elongating excessively. The central zone provides clear vision for everyday activities.
MiYOSMART
With the exclusive non-invasive D.I.M.S. Technology, the lens corrects the visual defect on its entire surface and has a ring shaped treatment area to slow down myopia progression. The alternation of the focus area and defocus area provides clear vision and manages myopia simultaneously. In 2018, the MiYOSMART® lens won the Gold Prize, Grand Award & Special Gold Award International Exhibition of Inventions of Geneva, Switzerland. In 2020, it won the Silmo d’Or Award in the Vision category at the Silmo Paris Optical Fair.

Essilor® Stellest® Lenses

  • H.A.L.T.® Technology (Highly Aspherical Lenslet Target)
  • Technology Overview: H.A.L.T. technology uses a series of highly aspherical lenslets arranged in a ring around the lens center to create multiple focal points.
  • Advantages: The aspherical design allows for precise defocus effects at the peripheral retina, while the central clear zone ensures excellent vision for normal tasks. This multifocal approach disrupts the signals that promote eye elongation.
Stellest
Stellest® lenses use H.A.L.T.® technology to invisibly distribute 1021 micro lenses on the star rings to form a deceleration shield that slows down the progression of myopia, thereby slowing down the progression of myopia. The results of the 2-year clinical study of Stellest® lenses were published in the world's famous SCI ophthalmology journal "JAMA Ophthalmology".

Zeiss® MyoCare® Lenses

  • C.A.R.E.® Technology (Cylindrical Annular Refractive Element)
  • Technology Overview: C.A.R.E. technology employs cylindrical annular refractive elements arranged in concentric rings that dynamically alter the light entering the eye.
  • Advantages: This dynamic light modulation ensures that the defocus effect covers the entire visual field, providing consistent myopia control, even as the eye moves. The lens's back surface is custom-designed to enhance personalization and comfort.
MyoCare
The ZElSS® MyoCare® lens is designed to introduce a mechanism of action (a signal) at the retina of the eye to help slow the progression of myopia. The lens has ring shaped elements that alternate with zones that correct for distance refractive error of the eye.In combination, they deliver simultaneous myopic defocus, or in other words, the eye receives simultaneous competing blur and clear images, at the retina of the eye. A central clear area that does not contain the ring like elements corrects the distance refractive error.

Technology Comparison

Defocus Generation Mechanism

  • D.I.M.S.® Technology: Uses alternating zones of defocus and clear vision segments.
  • H.A.L.T.® Technology: Utilizes highly aspherical lenslet arrays to create multiple focal points.
  • C.A.R.E.® Technology: Employs concentric rings of cylindrical elements for dynamic light modulation.

Defocus Zone Design

  • D.I.M.S.® Technology: Equally distributed defocus and clear vision zones.
  • H.A.L.T.® Technology: Central clear zone with surrounding ring of lenslets.
  • C.A.R.E.® Technology: Concentric ring design ensuring full-field coverage.

Dynamic vs. Static Defocus

  • D.I.M.S.® Technology: Provides consistent defocus across the lens.
  • H.A.L.T.® Technology: Focuses on fixed multifocal points.
  • C.A.R.E.® Technology: Offers dynamic light modulation to maintain consistent defocus with eye movement.

Clinical Effectiveness of Multifocal Defocus Lenses

Numerous studies and clinical trials have demonstrated the effectiveness of multifocal defocus lenses in controlling myopia progression. Each technology—D.I.M.S, H.A.L.T., and C.A.R.E.—has shown substantial reductions in the rate of myopia progression in children compared to traditional single-vision lenses. These outcomes reinforce the potential of multifocal defocus lenses as a critical tool in addressing the growing myopia epidemic.

Usage Recommendations

  • Target Audience: Multifocal defocus lenses are primarily recommended for children and adolescents, particularly those with rapidly progressing myopia.
  • Choosing the Right Lens: Selection should be based on individual visual needs, lifestyle, and the specific recommendations of an eye care professional.
  • Regular Eye Examinations: Consistent follow-up and eye examinations are crucial to monitor myopia progression and adapt the lens prescription as needed.

Conclusion

Multifocal defocus lenses represent a significant advancement in the quest to control myopia progression. With innovative technologies like D.I.M.S, H.A.L.T., and C.A.R.E., these lenses provide effective solutions for reducing the rate of myopia progression while ensuring clear vision. As technology continues to evolve, the future holds promise for even more refined and effective methods to combat the myopia epidemic.

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