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Optical aberrations
Anatomy & Optics
Key Points
- •Lower-order aberrations (defocus + astigmatism) account for ~85% of total ocular aberrations and are correctable with spectacles/CL; higher-order aberrations (~15%) require wavefront-guided approaches
- •The 5 Seidel monochromatic aberrations are: spherical aberration, coma, oblique astigmatism, curvature of field, and distortion
- •Zernike polynomials provide the mathematical framework for describing wavefront aberrations - each polynomial represents a specific aberration mode ordered by radial order and angular frequency
- •The young crystalline lens has negative spherical aberration that partially compensates for corneal positive spherical aberration; this balance is lost with ageing
- •The duochrome test exploits longitudinal chromatic aberration (~2 D): red clearer = under-corrected (needs more minus); green clearer = over-corrected
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17 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Risk factors and associations