The curvature of the cornea, which provides its refractive power.

Used both AL and K to predict ELP. These remain widely used today.

Used a simple regression equation; often inaccurate for very long or short eyes.

These use complex variables (like anterior chamber depth and lens thickness) or Artificial Intelligence to account for the eye's unique geometry. Challenges and Precision

Patients who have had LASIK or PRK have altered corneal shapes that traditional formulas often miscalculate.