Spectral domain technology is an evolution
Michael S. Ip
Optical coherence tomography, in general, is a very valuable diagnostic
tool that can help with diagnosis, but also in management of patients. For
example, it can show response to treatment when you follow patients
longitudinally and can depict resolution of a condition. OCT is also a lot less
invasive than the other commonly used and helpful tools we use in the retinal
clinic, and that would be angiography, either fluorescein or ICG. OCT is a
faster, less expensive, better tolerated procedure.
The utility of OCT will, of course, depend on the disease. I would say
in the assessment of vitreoretinal interface disease, early stage macular hole,
epiretinal membrane or even a full thickness macular hole, OCT provides
information that you cannot get from any other ancillary test. I put a high
level of importance on the findings from OCT with my patients who have retinal
For the majority of patients that come into a clinic on a typical day,
OCT has now become an indispensable tool for evaluation, but still, you cannot
use OCT in lieu of everything else. In terms of macular degeneration,
fluorescein angiography will show you leakage that you cannot see on OCT. In
terms of other ancillary tests, function of the retina is best demonstrated by
electroretinography, and that is something that you will not get with OCT.
Spectral domain does add a level of resolution to the images, and it
gives us a better look at the anatomy than time domain. But I would liken the
development of time domain OCT over the era that we did not have time domain
OCT as a revolutionary step forward, whereas I would call the change to
spectral domain from time domain more of an evolutionary change. In other
words, it is a step forward, but it is not as great as the step from no OCT to
time domain OCT.
Michael S. Ip, MD, is an associate professor of ophthalmology
at the University of Wisconsin.
OCT is only part of the picture
Spectral domain optical coherence tomography is an important clinical
and research tool, but results should be interpreted against other clinical
tests and observations.
José G. Cunha-Vaz
I think spectral domain OCT is important for evaluating macular edema,
for example, because it provides accurate information, especially with regard
to the mapping of retinal thickness and the central 500 µm. Future
research should look closer at the implications of retinal thickness and
whether the ability to more accurately measure retinal thickness might have
clear clinical implications.
OCT findings are fundamental for following patients with macular edema,
but results should not be used in isolation. In order to get a complete
clinical picture that will allow proper decision making, we need additional
data, including best corrected visual acuity; microperimetry; information on
leakage, preferably from scanning laser ophthalmoscope leakage analysis; and
information on capillary closure, at least from the central foveal avascular
zone. The more combined information we will get in the neat future, the more we
will rely on the findings from spectral domain OCT.
José G. Cunha-Vaz, MD, PhD, is the chair of
ophthalmology at the University of Coimbra, Portugal.