Optical Biometry Explained

Optical biometry is the current standard for intraocular lens (IOL) power calculations in clinical practice. Optical biometry is a highly accurate non-invasive automated method for measuring the anatomical characteristics of the eye. Accurate measurements are critical for determining the correct power of an IOL before it is implanted during cataract surgery .

Before implantation the correct lens power needs to be determined. The process of measuring the various anatomical characteristics of the eye that are needed for IOL power calculation is called ocular biometry. Optical biometry, also known as ophthalmic biometry, using partial coherence interferometry has become the gold standard in ocular biometry as it is highly accurate, easy to perform, non-invasive and comfortable for the patient. The accuracy of optical biometry, and in particular the Lenstar and IOL-Master, have been extensively confirmed across a wide range of scientific studies.

The use of optical biometry is a valuable tool when planning cataract surgery, resulting in optimization of patient outcomes.


What is ocular biometry?

Ocular biometry involves anatomical measurements of the eye, including the axial length (AL), keratometry and anterior chamber depth (ACD) and includes anterior segment biometry, for which only the front third of the eye is measured. These biometric measurements are crucial for the selection of the correct IOL power in order to achieve the desired refractive outcome after cataract surgery.1 Therefore, ocular biometry is an essential step before cataract surgery. There are currently two procedures available: ultrasound and optical biometry. Due to certain disadvantages of ultrasound biometry, optical biometry has become procedure of choice in ocular biometry.


It all started with ultrasound biometry

Ultrasound biometry is an invasive procedure that requires direct contact with the cornea and the use of anesthetics, both of which can be uncomfortable for the patient. Moreover, this measurement method requires significant training for the examiner in order to avoid errors due to excessive compression of the ultrasound probe on the cornea. Ultrasound biometry also requires adjustment of the ultrasound speed when different media and/or optical conditions are present, e.g. pseudophakic eyes and silicone oil.

1. LENSTAR Biometry


While the introduction of optical biometry revolutionized cataract surgery in the late 1990s, Haag-Streit is writing the latest chapter in biometry history with Lenstar.

Lenstar provides highly accurate laser optic measurements for every section of the eye − from the cornea to the retina. With its integrated Olsen formula and the optional Toric Planner featuring the Barrett Toric Calculator, Lenstar supplies the user with latest technology in IOL prediction for any patient.

Measured parameters

Biometry of the entire eye in a single measurement

Lenstar simultaneously provides laser interferometric biometry of the entire eye, precise keratometry, astigmatism and axis measurement, WtW and pupillometry simultaneously in a single measurement.
EyeSuite IOL features cutting-edge multivariable IOL formulae for improved refractive outcomes.


The ZEISS IOLMaster® 500 is the gold standard in optical biometry with more than 100 million successful IOL power calculations to date. With the new version of the ZEISS IOLMaster 500 you get a piece of cutting-edge technology that points the way to the future of optical biometry.

  • Improving refractive outcomes: Any intraocular lens calculation is only as reliable as the lens constant it is based on. More than 40,000 sets of patient data created with the ZEISS IOLMaster are the basis of more than 200 optimized lens constants in the User Group for Laser Interference Biometry (ULIB) website – absolutely unique in the industry. Together with its one-of-a-kind distance independent telecentric keratometry (watch video) and the exclusively integrated Holladay 2 formula, the gold standard in optical biometry helps you improve your refractive outcomes.
  • Advanced measurement of challenging eyes: The true test of a biometer is its performance with challenging eyes. In denser cataracts the ZEISS IOLMaster 500 achieves a measurement success ratio that is up to 20% higher than that of other optical biometry devices. Even with staphyloma, pseudophakic and silicone-filled eyes the ZEISS IOLMaster 500 measures along the visual axis, yielding the relevant axial distance. And with its Haigis-L formula on board the ZEISS IOLMaster 500 is dedicated to myopic and hyperopic post-LVC cases.
  • Proven toric outcomes: The results of a meta-analysis of 28 published clinical papers covering more than 1900 cases show that the reported clinical outcomes for the ZEISS IOLMaster with regard to residual astigmatism “[…] exceed, or are at least as good as those using manual or automated keratometry
  • Ease of use: A well-designed user interface, plausibility checks, distance-independent measurements and an up to 4 times faster reading compared to other optical devices lead to a one-of-a-kind usability and reduced chairtime. A difference you, your team and your patients will notice every day.