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).
Purpose:
To compare axial length (AL) measurements obtained by optical biometry (OB) and immersion ultrasound (iUS) to investigate the agreement between the 2 techniques and how to use OB constants for eyes with AL by iUS.
Setting:
Multicenter study.
Design:
Retrospective observational case series.
Methods:
Agreement between OB and iUS ALs was investigated in 4 subsets. Also, in a test database, the prediction error (PE) for iUS AL was assessed with 4 methods: (1) data-optimized constants; (2) user group for laser interference biometry (ULIB) constants with iUS biometry; (3) with recalibrated AL; and (4) ULIB A-constant - 0.23.
Results:
A Combined 1970 eyes were measured with both OB and iUS biometry. OB mean AL was 0.0873 mm longer than iUS AL. The latter was made equivalent to OB ALs with this equation: Recalibrated iUS AL = 1.0228 × iUS AL - 0.4556. In a fifth database (n = 1079) with OB AL measurements only, after AL was artificially shortened by 0.0873 mm, the original A-constant had to be reduced by 0.23 to maintain a zero PE. In a sixth database (n = 127) with iUS AL, the original ULIB A-constant provided the poorest outcomes. Using either recalibrated iUS AL or ULIB A-constant - 0.23 zeroed out the mean PE and achieved the lowest median absolute error.
Conclusions:
AL measurements by iUS can be used with ULIB constants for OB by subtracting 0.23 from the A-constant; alternatively, the iUS AL may be recalibrated. The recalibrated iUS AL should be treated as AL measurements obtained by OB. It is longer than iUS AL in long eyes.
