Biometry is the measurement of the eye's physical dimensions. To calculate the correct IOL power, surgeons need two primary measurements:
Measuring "Total Corneal Power" (both the front and back of the cornea) is essential for Toric IOLs, which correct astigmatism.
Once measurements are taken, they are plugged into mathematical formulas to predict the necessary lens power. These formulas have evolved through "generations" based on how they estimate the —the final resting place of the IOL in the eye. Biometry & IOL Power Calculations - PDF
Biometry and Intraocular Lens (IOL) power calculations are the cornerstone of modern cataract surgery, transforming the procedure from simple lens removal to a precise refractive intervention. The goal is no longer just to restore sight, but to achieve "refractive neutrality" or a specific target vision without the heavy reliance on glasses. The Role of Biometry
Historically, was the standard. It used sound waves to measure distance but required physical contact with the eye, which could compress the cornea and lead to errors. Today, Optical Coherence Biometry (like the IOLMaster or Lenstar) is the gold standard. It uses light instead of sound, offering sub-millimeter precision and a non-contact approach that eliminates compression bias. Evolution of IOL Formulas Biometry is the measurement of the eye's physical dimensions
Used both AL and K to predict ELP. These remain widely used today.
Patients who have had LASIK or PRK have altered corneal shapes that traditional formulas often miscalculate. These formulas have evolved through "generations" based on
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