Related Experiment Video
Updated: Oct 13, 2025
Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter
Published on: September 16, 2025
Immersion ultrasound biometry vs optical biometry.
David L Cooke1, Rhonda Waldron, Giacomo Savini
1From the Great Lakes Eye Care, Saint Joseph, Michigan (Cooke); Department of Neurology and Ophthalmology, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan (Cooke); Emory Eye Center, Emory University Department of Ophthalmology, Atlanta, Georgia (Waldron); G.B. Bietti Foundation-I.R.C.C.S. Rome, Italy (Savini); Dean McGee Eye Institute, University of Oklahoma, Oklahoma City, Oklahoma (Riaz, Murphy); Eye Clinic, S. Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy (Taroni, Guaraldi).
Optical biometry (OB) and immersion ultrasound (iUS) axial length (AL) measurements show good agreement. Adjusting iUS AL with recalibration or a modified A-constant allows compatibility with OB constants for accurate refractive predictions.
Area of Science:
- Ophthalmology
- Biometry
- Optics
Background:
- Accurate axial length (AL) measurement is crucial for intraocular lens (IOL) power calculation.
- Optical biometry (OB) and immersion ultrasound (iUS) are common methods for AL measurement, but their agreement and interchangeability require investigation.
Purpose of the Study:
- To compare AL measurements from OB and iUS.
- To assess the agreement between OB and iUS AL measurements.
- To determine how to utilize OB constants with iUS AL measurements.
Main Methods:
- A multicenter retrospective observational study compared AL measurements from OB and iUS in 1970 eyes.
- Four methods were used to assess prediction error (PE) for iUS AL in a test database: data-optimized constants, user group for laser interference biometry (ULIB) constants, recalibrated AL, and ULIB A-constant - 0.23.
Main Results:
- OB mean AL was 0.0873 mm longer than iUS AL.
- A recalibration formula (Recalibrated iUS AL = 1.0228 × iUS AL - 0.4556) was derived to make iUS AL equivalent to OB AL.
- Using either recalibrated iUS AL or a modified A-constant (ULIB A-constant - 0.23) minimized mean PE and median absolute error in iUS AL measurements.
Conclusions:
- iUS AL measurements can be used with OB constants by subtracting 0.23 from the A-constant or by recalibrating the iUS AL.
- Recalibrated iUS AL should be treated as OB AL measurements.
- Recalibrated iUS AL is longer than the original iUS AL, particularly in long eyes.
