Haag Streit Lenstar optical biometry model
Precise biometry is essential for accurate outcomes in cataract and refractive surgeries. The measurement of axial length by ultrasound was the gold standard for many years. With the introduction of optical biometry in the United States in 2000, this technology has become increasingly popular and is now the most common method for measuring axial length. Optical biometry presents an accurate alternative for precise ocular measurements, used not only for axial length, but also for anterior chamber depth, lens thickness, pachymetry, and retinal thickness measurements.
Optical biometry utilizes a partially coherent wave that has approximately nine times the resolution of a 10 MHz sound wave, making the measurement of axial length very precise. The measurement technique also helps to avoid operator variations in the measurements. Additionally, increasing accuracy is the fact that contact with the cornea is not required, thereby eliminating variations due to compression on the cornea. Since optical biometry measures to the center of the macula, it provides the refractive axial length in comparison to the anatomic axial length achieved with ultrasound biometry.
Haag Streit – Lenstar®
The Haag Streit Lenstar allows measurements of not only axial length and keratometry, but also provides measurements for white-to-white distance, pachymetry, lens thickness, anterior chamber depth, pupillometry, eccentricity of the visual axis, and retinal thickness. The Lenstar also defines anterior chamber depth more accurately as the distance from the posterior surface of the cornea to the anterior surface of the lens, rather than the distance from the anterior surface of the cornea to the anterior surface of the lens, like many others do. The Lenstar takes keratometric readings at 1.65mm and 2.3mm, combining them via an iteration process for improved consistency.
All standard IOL prediction formulas (Hill RBF, Holladay I, SRK-T, Haigis, and Hoffer Q) are built into the software, with the potential for future formulas to be added. Since the Lenstar measures more parameters of the eye than traditional IOL formulas, the system is ready to incorporate future generations of IOL formulas as they are developed. As a recent addition, the Olsen formula can now be used for calculations. Constants for use with the Olsen formula are available from data acquired by Dr. Olsen. Furthermore, constants for the toric IOL are available from IOL manufacturers.
Visit our physicians’ download page to access the Lenstar User Manual.
Carl Zeiss Meditec – IOLMaster®
The IOLMaster was the first optical biometry model to be introduced to the market since 1999. Since then, many advances have been made in this technology. Although the IOL Master still provides accurate measurements, it uses slit imagery for some, while others have progressed to optical biometry. Improvements have been made on this unit since its first development. For instance, Zeiss improved the ability to reduce background noise when measuring through dense cataracts. The IOLMaster has a high-speed computer for the quick and reproducible acquisition of keratometry information. According to Carl Zeiss, the IOLMaster is consistently accurate to within 0.02 mm (compared to 0.10mm to 0.12 mm with A-scans).
Visit our physicians’ download page to access the IOLMaster User Manual.
