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Eye shape in emmetropia and myopia.
David A Atchison1, Catherine E Jones, Katrina L Schmid
1School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia. d.atchison@qut.edu.au <d.atchison@qut.edu.au>
Investigative Ophthalmology & Visual Science
|September 29, 2004
Summary
Myopic eyes show significant elongation in length, height, and width compared to emmetropic eyes. These ocular dimensions provide insights into myopia development models, revealing individual variations in eye expansion.
Area of Science:
- Ophthalmology
- Biomedical Imaging
- Refractive Error Research
Background:
- Myopia development is often associated with ocular expansion.
- Understanding the dimensional changes in myopic eyes is crucial for modeling myopia progression.
- Existing models may not fully capture the heterogeneity of ocular dimensions in myopia.
Purpose of the Study:
- To quantify axial, vertical, and horizontal eye dimensions in myopic and emmetropic individuals using magnetic resonance imaging (MRI).
- To correlate these ocular dimensions with established models of myopia development, specifically global expansion and axial elongation.
- To investigate the variability of these dimensions and their implications for myopia pathogenesis.
Main Methods:
- Magnetic resonance imaging (MRI) was employed to measure internal eye length, height, and width in 88 participants (myopic and emmetropic).
- Participants aged 18-36 years were scanned in a supine position, with specific sequences to obtain axial and sagittal eye sections.
- Measurements were taken from cornea to retina (length) and retina to retina (height and width).
Main Results:
- Myopic eyes exhibited increased dimensions across all measured axes compared to emmetropic eyes.
- Elongation was most pronounced in length (0.35 mm/D), followed by height (0.19 mm/D), and then width (0.10 mm/D).
- A significant proportion of myopic eyes (17-39%) exclusively fit either the global expansion or axial elongation models, indicating diverse expansion patterns.
Conclusions:
- Myopic eyes are generally more elongated than emmetropic eyes, with length showing the greatest increase, followed by height and then width.
- Individual variations in ocular dimensions are considerable, influencing how well eyes fit theoretical expansion models.
- Approximately a quarter of myopic participants exclusively aligned with either the global expansion or axial elongation model, highlighting the complexity of myopia development.