243
still an essential examination for studying CNV in patients
with AMD, and FA and ICGA are especially important
for identifying occult disease. When comparing both
techniques, because OCT is gaining definition with new
versions and devices, the non-invasive nature of FA and
ICGA takes precedence over conventional angiographic
techniques, to the extent that some studies have reported
similar results for both examinations. Krebs and colleagues
and Saddu and colleagues proposed that OCT can detect
signs of activity similar to FA in a study in which two inde-
pendent observers analyzed the agreement. The authors
reported that even OCT was slightly more sensitive than
FA for determining the activity of the membranes, while
other authors stated that it was necessary to manually
adjust the segmentation analysis of images to achieve simi-
lar results.
22,38
More recently, Malamos and colleagues used
high-definition OCT to analyze patients diagnosed by FA
with different types of AMD (early, neovascular classic,
minimally classic, and occult). They reported a significant
correlation between different angiographic patterns and
various parameters with OCT. The authors could discrimi-
nate different types of damage using OCT to the extent
that they could identify their precise anatomic retinal
maps.
39
In cases with hidden membranes and some cases
of RAP, the relevance of FA is undoubtedly even greater
because of the difficulty of localizing the pathology in the
tomography images (Figure 14). However, some authors
have described changes associated with OCT membranes,
such as exudation signs and the almost constant presence
of RPE detachments, and changes within the polymorphic
features of these lesions.
3
Until the development of new techniques to visualize the
choroid with OCT such as that proposed by Spaide and
colleagues, the most informative method to explore these
cases is FA.
0-42
However, OCT seems to override FA in
the identification of signs of activity in patients previously
treated with PDT, in which interobserver agreement is
much higher for OCT than for FA.
43-44
Finally, the sequen-
tial use of both techniques for screening of wet AMD in
patients with impaired visual acuity (VA) has been pro-
posed. The screening was first performed with OCT and
then based on the results, fluorescein and indocyanine FA,
which obtained adequate sensitivity and specificity for the
early detection of AMD in these patients.
45
13. OCT and Autofluorescence
Autofluorescence allows gathering of information about
the metabolic status of the retina. This technique based
on the ability of tissues to emit more or less fluorescence
depending on the amount of accumulated lipofuscin to
be excited by light at specific wavelengths and provides
the opportunity to evaluate the retinal functional sta-
tus. Since OCT obtains a detailed picture of the retinal
anatomy, several studies have evaluated the structure/
function in patients with AMD and correlated the two
techniques. Bearelly and colleagues
46
reported that there
was a significant association between OCT and autofluo-
rescence findings and that marked hyperfluorescence at
the edges of the plaques of GA correlated with hyper-
reflective changes in the outer retinal layers identified by
OCT that did not occur in healthy retinas with normal
autofluorescence and OCT (Figure 15).
These findings used a combination of both techniques to
determine the patterns of progression of GA plaques in
patients with AMD, which had been targeted previously
by other authors as discussed below.
47
Autofluorescence
currently is the most frequently used test to assess dis-
ease progression in dry AMD; however, OCT provides
additional information, so its role has not been ruled out
in the study of these patients to the extent that some
authors have proposed methods based on OCT to evalu-
ate progression of atrophic plaques, as described in the
following section.
17
OPTICAL COHERENCE TOMOGRAPHY IN AGE-RELATED MACULAR DEGENERATION
