Among the three most popular optical coherence tomography and angiography devices, there are important differences in hardware, resolution and the manner in which the data are analyzed and displayed.
Reviewed by Angelo P. Tanna, MD
Spectral-domain optical coherence tomography (SD-OCT) technology has been progressively advancing in recent years. In the United States, some commonly used instruments are currently manufactured by Optovue, Inc., Heidelberg Engineering, and Carl Zeiss Meditec.
While these are common devices, the features among them differ, according to Angelo P. Tanna, MD, vice chairman and associate professor of ophthalmology and director of the Glaucoma Service, Northwestern University Feinberg School of Medicine, Chicago.
For example, the Cirrus 5000 SD-OCT system from Carl Zeiss Meditec has two different detectors that operate at different scan speeds, i.e., 27 mHz for OCT imaging and 68 mHz for OCT angiography (OCTA).
Dr. Tanna said he believes that these differences in scan speed and resolution among the different SD-OCT platforms result in differences in the quality of the images.
He demonstrated that the Spectralis OCT2 system from Heidelberg Engineering has exceptional image quality and very high effective resolution because its 85 mHz scan speed allows multiple scans can be obtained and averaged and results in reduced motion artifact.
Normative databases are important. All of the instruments have robust ethnically diverse normative data. However, a drawback for all of the OCT devices is that a comparison of a specific patient to his or her ethnic group within the database is not possible.
Patients are compared to an age-similar group of norms, Dr. Tanna noted. Another difference is the manner in which the macular thickness is measured among the instruments.
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Angelo P. Tanna, MD
E: [email protected]
This article is based on Dr. Tanna’s presentation at the American Glaucoma Society 2019 annual meeting in San Francisco. Dr. Tanna is a consultant to Carl Zeiss Meditec