Efficacy of Highly Aspherical Lenslet (HAL) spectacles in slowing myopia progression in children and adolescents: A multi-centre, retrospective, real-world study in India-SOLIDITY study

This multi-centre retrospective study in India demonstrates that Highly Aspherical Lenslet (HAL) spectacles significantly slowed myopia progression by approximately 83% and axial elongation by 62% in children and adolescents aged 4 to 16 years compared to expected physiological rates.

The Gist

Imagine your child's eyes are like a growing camera. For a camera to take a sharp picture, the film (the retina) needs to be at just the right distance from the lens. In a child with myopia (nearsightedness), the camera body is growing too long too fast. This stretches the film, making distant things look blurry.

The goal of myopia control isn't just to give them glasses to see clearly today; it's to put a "brake" on that camera body so it doesn't stretch out too much, preventing the vision from getting worse over time.

Here is what the SOLIDITY study from India discovered, explained simply:

The Experiment: A Real-World Test

Researchers looked back at the medical records of 372 children (ages 4 to 16) across 10 different eye clinics in India. They wanted to see if a new type of special glasses, called HAL lenses (Essilor Stellest), actually worked in the real world, not just in a strict lab setting.

Think of these special lenses as a smart traffic controller for light entering the eye. Unlike regular glasses that just focus light on the center, these lenses send a signal to the eye to "stop growing" while still letting the child see clearly.

The Timeline: Before, During, and After

The researchers compared three time periods for each child:

1. The "Wild Growth" Year (T1): The year before they got the special glasses.
2. The Start Line (T2): The moment they got the HAL glasses.
3. The "Controlled" Year (T3): The 6 to 24 months after wearing the glasses.

The Results: Slowing the Race

Here is the magic number breakdown:

• Without the special glasses: The children's eyes were stretching out (getting longer) at a fast pace. Their vision got worse by about -0.72 units (called Diopters) every year. It was like a car speeding down a hill.
• With the special glasses: The speed dropped dramatically. Their vision only worsened by -0.11 units a year.
• The Comparison: The researchers used a computer model to predict how much the eyes would have grown if they hadn't worn the glasses. The special glasses slowed down the eye's growth by a massive 83%.

The "Stretch" Analogy:
Imagine a rubber band representing the eye.

• Normal growth: The rubber band stretches 0.29 mm every year.
• With HAL glasses: The rubber band only stretches 0.11 mm every year.
• The Result: The glasses successfully slowed the stretching by about 62%.

The Bottom Line

This study is like a real-world report card for these special glasses. It confirms that for Indian children, wearing these HAL lenses is a highly effective way to hit the "pause button" on worsening nearsightedness.

A Small Caveat:
Because this study looked back at old records (like reviewing a diary) rather than watching kids in a controlled experiment from start to finish, the researchers say we need more long-term studies to be 100% sure. But for now, the evidence is very strong: these glasses are a powerful tool to keep children's eyes from growing too long.

Technical Summary

Technical Summary: Efficacy of HAL Spectacles in Myopia Control (SOLIDITY Study)

1. Problem Statement

Myopia progression in children and adolescents is a significant global public health concern, leading to increased risks of sight-threatening pathologies later in life. While various optical interventions exist, there is a critical need for real-world evidence (RWE) validating the efficacy of new myopia control technologies, specifically Highly Aspherical Lenslet (HAL) spectacles (Essilor® Stellest®), within diverse demographic populations. Prior to this study, data on the performance of HAL lenses in the Indian population was limited, necessitating an evaluation of its effectiveness outside of controlled clinical trial settings.

2. Methodology

The SOLIDITY study was designed as a multi-centre, retrospective, real-world study conducted across 10 leading ophthalmic centers in India.

• Study Population: The cohort included 372 myopic children and adolescents aged 4 to 16 years who were prescribed HAL spectacles.
• Data Collection: Data was extracted from electronic medical records (EMR) at three distinct time points:
  • T1: One year prior to the intervention (untreated period).
  • T2: Baseline at the time of HAL spectacle prescription.
  • T3: 6 to 24 months post-prescription (follow-up period).
• Analytical Approach:
  • Unilateral Analysis: Only data from the right eye was analyzed to avoid inter-eye correlation issues.
  • Comparative Framework: The study compared actual myopia progression and axial elongation during the treatment period against two benchmarks:
    1. The individual's untreated progression (T1 to T2).
    2. Expected physiological progression derived from published meta-regression models, adjusted for age-related slowing of myopia.
• Primary Endpoints: Annual myopia progression (in Diopters, D) and axial elongation (in millimeters, mm).

3. Key Contributions

• Real-World Validation: This study provides the first robust real-world evidence for HAL lens efficacy specifically within the Indian pediatric population, bridging the gap between clinical trial data and clinical practice.
• Advanced Modeling: Unlike simple pre-post comparisons, the study utilized trajectory-adjusted meta-regression models to estimate expected physiological progression. This allowed for a more accurate calculation of the "treatment effect" by accounting for the natural slowing of myopia progression as children age.
• Comprehensive Metrics: The study simultaneously evaluated both refractive error (spherical equivalent) and anatomical changes (axial length), providing a holistic view of myopia control efficacy.

4. Key Results

The study demonstrated a statistically significant reduction in both myopia progression and axial elongation:

• Myopia Progression (Refractive Error):

  • Untreated Rate: -0.72 ± 0.47 D/year.
  • Treated Rate (HAL): -0.11 ± 0.29 D/year.
  • Expected Untreated (Model-based): -0.65 D/year.
  • Treatment Effect: The HAL lenses resulted in a 0.54 D/year reduction in progression, corresponding to an estimated 83% slowing of myopia progression compared to the expected physiological trajectory.

• Axial Elongation:

  • Expected Physiological Rate: 0.29 mm/year.
  • Treated Rate (HAL): 0.11 ± 0.16 mm/year.
  • Treatment Effect: The intervention achieved a relative slowing of axial elongation of approximately 62%.

5. Significance and Limitations

• Clinical Significance: The findings validate HAL spectacles as a highly effective intervention for slowing myopia progression in Indian children, supporting their adoption in clinical practice for myopia management. The 83% reduction in refractive progression and 62% reduction in axial elongation are clinically meaningful outcomes that may reduce the risk of high myopia-related complications.
• Limitations & Future Directions:
  • Retrospective Design: As a retrospective study, it is subject to potential selection bias and lacks the rigorous control of a randomized controlled trial (RCT).
  • Follow-up Duration: The follow-up period (6–24 months) is relatively short for long-term myopia management studies.
  • Recommendation: The authors emphasize the need for prospective, long-term studies to confirm these findings and assess the durability of the treatment effect over extended periods.

In conclusion, the SOLIDITY study successfully establishes HAL lenses as a potent tool for myopia control in a real-world Indian setting, offering substantial protection against both refractive and axial progression.