Please check out our Wavefront Aberrometry Systems section for more information about the products mentioned in this article.
Aberrometers use wavefronts to objectively measure overall refractive error and have been a very useful tool in ophthalmology, particularly in refractive surgery. They differ from auto refractometers and corneal topographers in that they measure lower and higher order aberrations due to corneal and lenticular changes. Because of this technological breakthrough, ophthalmologists are able to accurately and precisely measure more correcting elements of the eye than were ever imaginable.
Hartmann-Shack is the wavefront technology that is most popular among manufacturers and uses one shot to measure a wavefront, which not only makes it quick, but repeatable as well and produces high-resolution evaluations. In comparison, ray tracing uses consecutive measurements completed over several sampling points within milliseconds so that eye movement does not affect the measurement. This technique can detect large magnitude errors of reflection.
Hartmann-Shack aberrometers vary in their degree of accuracy, dynamic range, max/min pupil diameters, analysis features and compatibility with other devices. Accuracy and dynamic range seem to be 2 of the most important factors when choosing an aberrometer. Accuracy corresponds to the number and spread of points measured. The higher the number of points the better, but the spread must be even. Dynamic range corresponds to the device’s ability to detect the higher and lower ranges as well as the subtleties in variations. Overall dynamic range can be gauged by cylinder range. Less precise wavefront sensors may not detect disorders such as keratoconus, corneal scarring and severe high order aberrations.
Some manufacturers use software interpolation to enhance the optical resolution of the wavefront sensors. Instead of physically measuring each point, the computer takes data from nearby points to calculate and approximate the measurement, leaving more room for error.
Discussed below are aberrometers from 5 different manufacturers: Marco, Nidek, Topcon, Ziemer, and Bausch & Lomb.
Marco 3-D Wave Refractive Diagnostic Workstation
This device combines 4 technologies into one workstation. Refraction, corneal topography, optical path difference and wavefront analysis can be obtained so that refractive and cataract surgery screenings can be performed, post-operative complaints can be evaluated and pathology diagnoses determined. This device has the capability to image mesonic and photopic pupils, evaluate all eyes not correctable to 20/20, compare objective to subjective point spread function, evaluate post-op tilt, decentration, multifocal optics, assess contact lens candidates for soft vs. hard lens wear, orthokeratology, and evaluate corneal aberrations secondary to certain lid and ocular surface pathologies. The measurable range for corneal refractive power is 33.75D – 67.50D, corneal astigmatism is 0D to ±12D, and axis angle 1°/5°.
Nidek OPD-Scan II Wavefront Aberrometer
This device has many more data points than other aberrometers allowing precise mapping of irregular astigmatism via a single step measurement of corneal topography and refractive error data. This aberrometer includes analysis of refractive power, wavefront, autorefractor, keratometer, placido disk technology, and contact lens fitting software. Measurement range is sphere -20D to +22D and cylinder 0D to ±12D.
Topcon iTrace Combo Visual Function Analyzer
This Topcon device uses ray tracing technology for wavefront and refractive analysis. Features include binocular and monocular open field fixation that eliminates patient accommodation, over spectacle refraction and wavefront measurements, the potential to auto-identify patient visual complaints, and a retinal spot diagram that provides graphical images of patients’ total refraction, aberrations and point spread.
Topcon KR-9000PW Wavefront Analyzer
As opposed to the unit described above, this device uses Hartmann-Shack technology. It combines an autorefractor, keratometer, corneal mapping system and wavefront analyzer. The KR-9000PW allows sphere, cylinder and axis measurements and evaluates spherical aberrations, coma and other high order aberrations of the eye. It offers simultaneous measurements of wavefront aberrations and corneal topography.
Ziemer Maxwell™ Optical Wavefront Aberrometer
This instrument allows assessment of all of the wavefront aberrations present in a patient’s eye and functions on greater than 99% of patients. The measurement range for sphere is -15D to +20D and cylinder -10D to +10D. There is a large area of analysis with high spatial resolution.
Bausch & Lomb Zyoptix® Diagnostic Workstation
This Hartmann-Shack device utilizes the Technolas® 217z Zyoptix® System for personalized vision correction. This workstation unites the Zywave® II Wavefront Aberrometer and the Orbscan® IIz Anterior Segment Analysis System, combining information on refractive error and corneal architecture. The measurement range for sphere is +6D to -12D and cylinder 0D to 5D. The device allows total wavefront analysis through the 5th order, 8mm pupil diameter.
Wavefront aberrometry is a breakthrough in ophthalmology, providing diagnostic information that was previously unattainable and unimaginable. With the multitude of applications for its use, any ophthalmology practice will experience benefits when it comes to patient care.
Please see the products listed below, or check out our Wavefront Aberrometry Systems section for more information.