Pre-treatment observation of axial elongation for evidence-based selection of children in Hong Kong for myopia control

Purpose: This study aimed to develop evidence-based guidelines for identifying suitable subjects for myopia control using orthokeratology (ortho-k). Methods: Changes in axial elongation (AE) in the worse eyes of 66 myopic children (myopia between -0.75 and -4.50 D and astigmatism < 2.00D, and aged 6 to < 16 years old) who wore single-vision spectacles for seven months before switching to orthokeratology treatment for another seven months were observed. Results: AE during ortho-k lens wear was affected by age and rate of progression during spectacle wear. The percentage of subjects with rapid, moderate, and slow AE (equivalent annual myopia progression; rapid: >= 1.00D; moderate: 0.50D to < 1.00D; slow: < 0.50D) during spectacle wear was 36.3%, 33.3% and 30.3%, respectively. Rapid progression was most common in subjects aged less than nine, but 25% of subjects aged 9 to < 13 and 12.5% aged 13 to < 16 also demonstrated rapid progression. All subjects with rapid AE during spectacle wear achieved a significant reduction in eye elongation with ortho-k lens wear. Guidelines for patient selection was proposed based on the initial age and history of myopia progression. Conclusions: Myopia control is indicated for children at risk of developing high myopia. The suggested guidelines can help practitioners to identify children for whom the benefits outweigh the risks of serious adverse events.