Orthokeratology Today: Topography Tells the Tale

Overview

Topography is the most informative tool for assessing orthokeratology lens fit, providing critical insights into lens centration, treatment zone size, and corneal power changes. Differentiating between axial and tangential maps enhances clinical evaluation and troubleshooting, while treatment zone decentration may influence myopia control outcomes.

Background

Orthokeratology (ortho-k) involves reshaping the cornea with specially designed lenses worn overnight to temporarily reduce myopia. Proper lens fit is essential for effective treatment and patient comfort. Corneal topography maps, including axial, tangential, and difference maps, are used to evaluate lens performance and corneal changes. Understanding these maps helps clinicians optimize lens fit and monitor treatment progression.

Data Highlights

Key referenced studies include Gong et al (2024), demonstrating that smaller treatment zones correlate with stronger myopia control in younger patients, Wang and Yang (2019) showing treatment zone decentration's influence on myopia progression, and Hiraoka et al (2015) linking ocular wavefront aberrations to axial length elongation in myopic children treated with ortho-k.

Key Findings

• Topography provides the most comprehensive data for assessing ortho-k lens fit, revealing lens behavior in a closed-eye environment.
• Axial maps are best for assessing overall corneal power changes and optical quality, while tangential maps offer detailed information on treatment zone size, shape, and centration.
• Difference maps are essential for monitoring corneal changes between visits and evaluating treatment stability and progression.
• Treatment zone decentration patterns (inferior, superior, horizontal) provide clues about lens fit and corneal shape, with some decentration potentially enhancing myopia control.
• Not all decentration requires correction if vision and corneal health remain stable; clinical judgment is necessary.
• Mechanical fit issues should be addressed before making optical adjustments to optimize lens performance and patient comfort.

Clinical Implications

Clinicians should prioritize tangential maps for evaluating lens fit and axial maps for assessing refractive changes. Monitoring treatment zone size relative to pupil diameter is important, especially in younger patients for myopia control and in teenagers to reduce night vision disturbances. Recognizing and managing lens decentration appropriately can improve treatment outcomes and patient satisfaction.

Conclusion

Mastering corneal topography interpretation is vital for effective orthokeratology lens fitting and management. Utilizing axial, tangential, and difference maps enhances clinical decision-making, improving myopia control and patient visual quality.

References

1. Gong et al, 2024 -- Efficacy of orthokeratology lens with the modified small treatment zone on myopia progression and visual quality
2. Wang and Yang, 2019 -- Influence of overnight orthokeratology lens treatment zone decentration on myopia progression
3. Hiraoka et al, 2015 -- Influence of ocular wavefront aberrations on axial length elongation in myopic children treated with overnight orthokeratology