1. Introduction

Myopia is a growing global epidemic. By 2050, it is estimated that nearly 50% of the world population will be myopic, with up to 10% having high myopia [1]. High myopia (≤ -6.00 D) is associated with increased risks of irreversible visual impairment due to complications such as retinal detachment, myopic macular degeneration, and glaucoma [2,3]. Excessive axial elongation of the eyeball is a primary structural feature of progressive myopia and serves as a predictor of long-term visual prognosis [4]. Therefore, controlling axial elongation has become central to modern myopia management strategies.

Among various interventions, optical strategies such as defocus lenses that manipulate retinal image quality to alter ocular growth have received considerable attention. This review discusses the theoretical foundation, types, and clinical effectiveness of defocus lenses, with emphasis on Defocus Incorporated Multiple Segments (DIMS) and center-distance multifocal soft contact lenses.

2. Background: Mechanisms of Myopia and Axial Elongation

The process of emmetropization enables the eye to adjust its axial length in response to defocus signals during early development [5]. Inappropriate retinal image defocus, especially peripheral hyperopic defocus, may drive axial elongation and myopia progression [6]. Experimental studies in animal models have consistently shown that the eye grows in response to hyperopic defocus and that myopic defocus suppresses ocular elongation [7,8].

These principles have translated into clinical strategies aimed at manipulating peripheral retinal defocus to inhibit abnormal ocular growth. Specifically, defocus lens technologies aim to provide clear central vision while simultaneously imposing myopic defocus peripherally, thus signaling the retina to decelerate axial elongation [9].

Figure 1

3. Optical Defocus Lenses for Myopia Control

3.1 Defocus Incorporated Multiple Segments (DIMS) Lenses

The DIMS spectacle lens, developed by Hong Kong Polytechnic University, has a central 9 mm optical zone for distance correction and an annular zone embedded with multiple myopic defocus segments of +3.50 D [10]. This configuration provides constant peripheral myopic defocus irrespective of gaze direction.

A pivotal 2-year randomized clinical trial by Lam et al. found that DIMS lenses reduced myopia progression by 59% and axial elongation by 60% compared to single-vision lenses [10]. A 3-year follow-up confirmed sustained efficacy without adverse effects [11]. DIMS lenses have since been validated in multiple populations, including Chinese, Japanese, and European children [12,13].

Figure 2

3.2 Stellest™ lenses

Stellest™ lenses by Essilor company are innovative spectacle lenses developed by Essilor for myopia control in children. They incorporate H.A.L.T. (Highly Aspherical Lenslet Target) technology, which features a central clear zone for sharp vision surrounded by concentric rings of aspherical lenslets that create a myopic defocus signal. This optical design aims to slow the elongation of the eyeball (axial length), a key factor in myopia progression.

Clinical studies have demonstrated that over a two-year period, children wearing Stellest™ lenses experienced approximately a 67% reduction in myopia progression compared to those wearing conventional single-vision lenses. Additionally, axial elongation, which is closely associated with the worsening of myopia, was reduced by about 60%, indicating that these lenses can significantly slow the structural changes in the eye that drive myopia progression. Importantly, this was achieved without compromising visual clarity or comfort, making Stellest™ lenses a promising option for myopia control in pediatric patients [14].

3.3 Multifocal Soft Contact Lenses

Center-distance multifocal soft contact lenses (e.g., MiSight 1 Day, Biofinity Multifocal) contain concentric treatment zones that create peripheral myopic defocus while preserving central vision [15]. The MiSight lens, in particular, is FDA-approved for myopia control in children aged 8–12 years [16].

The BLINK study compared single-vision lenses to multifocal lenses with +1.50 D and +2.50 D additions. After 3 years, the +2.50 D group had 43% less myopia progression and 38% less axial elongation than the control group [17]. Other studies, such as the DISC study in Hong Kong, reported a 25% reduction in axial elongation over 2 years with bifocal contact lenses [18].

4. Comparative Effectiveness and Outcomes

A comparison of key studies is shown below:

These outcomes suggest that defocus lenses significantly reduce both refractive progression and axial elongation in children. Compliance, early initiation, and consistent wear are critical to maximizing these benefits [19].

5. Limitations and Challenges

While defocus lenses are effective, inter-individual variability exists. Some children may not respond adequately, and predictive biomarkers are lacking [20]. Treatment efficacy is also influenced by compliance, baseline refractive error, ethnicity, and time spent outdoors [21].

Furthermore, long-term rebound effects after cessation of lens wear are not fully understood. Although DIMS lenses have shown sustained effects over 3 years [11], longer follow-up is required. Additionally, multifocal contact lenses carry risks of infection and require strict hygiene practices, which can be challenging in pediatric populations [22].

Cost and accessibility may also hinder widespread adoption, particularly in low-resource settings. Future research should focus on combining optical therapies with pharmacological agents like low-dose atropine to enhance outcomes [23].

6. Future Directions

Emerging technologies include extended-depth-of-focus (EDOF) lenses, spectacle lenses with gradient power profiles, and AI-powered smart lenses that adjust focus dynamically [24]. Personalized treatment algorithms based on biometric data and environmental exposure may soon allow clinicians to tailor interventions with greater precision.

Combining multiple treatment modalities, including behavioral strategies such as increased outdoor time, may further amplify treatment success [25]. Digital tools for monitoring lens wear compliance and axial growth in real time are also under development [26].

7. Conclusion

Defocus lenses represent a well-established, non-pharmacological approach for controlling myopia progression, primarily by targeting and slowing axial elongation. Clinical trials consistently demonstrate significant reductions in both refractive error progression and axial length increase when using optical interventions such as DIMS spectacle lenses, Stellest™ lenses, and center-distance multifocal soft contact lenses. Notably, DIMS lenses have shown up to 60% reduction in axial elongation over three years, while Stellest™ lenses have achieved up to 67% reduction in myopia progression. MiSight and other multifocal contact lenses also yield substantial benefits, albeit with varying efficacy based on lens design and patient compliance.

Despite the promising results, individual variability in response, dependency on adherence, and potential barriers related to cost and access remain challenges. There is a need for long-term data to assess sustained benefits and any rebound effects post-treatment cessation. Future directions, including the integration of digital compliance monitoring, AI-driven personalization, and combination therapies (e.g., with low-dose atropine), may enhance the overall effectiveness of myopia control programs.

In summary, defocus lenses are a clinically validated, safe, and increasingly accessible modality in pediatric myopia management. Their use, when combined with early intervention and supportive lifestyle strategies like increased outdoor activity, holds significant promise for reducing the global burden of myopia-related visual impairment.

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