Nonlinear and Asymmetric Refractive Sensitivity to Effective Lens Position Errors in Pseudophakic Eye Models

Area of Science:

• Ophthalmology
• Optical Engineering
• Biomedical Optics

Background:

• Accurate refractive outcomes after cataract surgery depend on precise intraocular lens (IOL) implantation.
• Effective lens position (ELP) is a critical parameter influencing postoperative refraction.
• Variability in ELP can lead to refractive surprises, necessitating a deeper understanding of its impact.

Purpose of the Study:

• To theoretically analyze refractive sensitivity to effective lens position (ELP) errors in pseudophakic eyes.
• To quantify the influence of axial length (AL) and corneal power on this sensitivity.
• To develop a vergence-based optical model for analyzing ELP-related refractive variability.

Main Methods:

• Developed a paraxial two-lens thin-lens model of the pseudophakic eye.
• Explicitly parameterized the model using axial length (AL), total corneal power (TCP), IOL power, and ELP.
• Calculated refraction using vergence propagation and simulated ELP perturbations across a wide biometric range.

Main Results:

• Refractive sensitivity to ELP errors is predominantly governed by axial length (AL).
• Shorter eyes exhibit higher refractive changes per millimeter of ELP error compared to longer eyes.
• Refractive error showed a nonlinear and asymmetric relationship with ELP displacement.

Conclusions:

• Refractive sensitivity to ELP errors in pseudophakic models is nonlinear and asymmetric.
• Axial length (AL) is the primary determinant of this sensitivity, with total corneal power (TCP) as a secondary modulator.
• The vergence-based framework provides a physical basis for understanding ELP-related refractive variability.