It goes without saying that the features that are paramount for any optical coherence tomography (OCT) instruments are image quality and the abilities to identify artifacts and interpret scans regardless of the desired structures to be viewed or the disease process involved.
The various commercially available devices work in different ways and understanding those differences may matter during evaluations.
Truth in imaging
In order to ensure image quality in spectral-domain OCT, the tissue image should be in the top third of the scanning window and the tissue should appear as flat as possible.
The condition of the ocular media, including a dry cornea, refractive errors, cataracts, and vitreous opacities can adversely affect the image quality, according to Joel S. Schuman, MD, professor of ophthalmology, neuroscience and physiology, neural science, biomedical engineering and electrical and computer engineering, and chairman of ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York.
According to the manufacturers, acceptable signal strengths and quality scores for the four most widely used OCT instruments are as follows: for the Cirrus (Carl Zeiss Meditec) and Avanti (Optovue), signal strengths of 6 or greater and 40 or greater, respectively, are acceptable and for Spectralis (Heidelberg Engineering and Triton, Topcon), quality scores of 20 or greater and 30 or greater are acceptable, according to Dr. Schuman.
In instruments in which acceptable images are not obtained, the results can be segmentation errors, i.e., incorrect measurements of tissue characteristics.