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Using Fundus
Autofluorescence
This is an essential tool for a definitive diagnosis.
By Karl G. Csaky, MD
F
undus autofluorescence (FAF) is yet another
diagnostic imaging modality that has drastically
changed due to advances in research and technology. Previous diagnostic techniques required the
injection of sodium fluorescein into the eye to highlight
structures such as optic nerve drusen. These structures
were then documented on high ISO film or monochrome
digital sensors, with inconsistent and unreliable results.
Today, diagnostic images can be captured by exciting
naturally occurring chemicals in the eye. These chemicals
absorb energy from light and then emit light at wavelengths longer than the excitation lightsource. This form
of autofluorescence occurs in structures such as optic
nerve drusen, astrocytic hamartomas, lipofuscin pigments
in the retina, and the aging crystalline lens.
Uses for FAF
FAF imaging provides information beyond that
obtained by imaging methods such as fundus photography or optical coherence tomography (OCT), and is particularly useful anytime there is unexplained vision loss
or when detailed information is needed about the retinal
pigment epithelium (RPE). It is a quick way to look at the
integrity of the RPE and determine if there are any changes in its level that may explain changes in vision. FAF is
also useful for defining the diagnosis of whitish deposits
seen via fundus examination, subretinal deposits identified by OCT imaging, or when looking for any pertubations of retinal epithelium. In central serous retinopathy,
Stargardt disease, adult vitelliform macular dystrophy
(AVMD), along with a host of other retinal dystrophies,
the lipofuscin leaves a very intense hyperfluorescence in a
striking pattern, allowing physicians to confirm any preliminary diagnosis made with other imaging techniques.
Finally, FAF makes it possible to precisely define areas of
geographic atrophy, and its use is a requirement with any
clinical trials in which geographic atrophy is relevant.
Figure 1. OCT image shows retinal elevation with
hyperreflective material.
Case Study
A 72 year-old woman was referred to me for possible
injection of anti-VEGF agents for the treatment of choroidal neovascularization (CNV) secondary to age-related
macular degeneration (AMD). The patient had noticed a
relatively sudden change in vision in her right eye and was
referred by a general ophthalmologist for a consultation.
The first step with any patient is a standard visual exam.
Her visual acuity in the right eye was 20/100 and 20/40 in
the left eye. Her examination was otherwise unremarkable, and she reported no past history of previous vision
problems, and her family’s ocular medical history was
unremarkable. The patient’s anterior segment appeared
normal with posterior chamber intraocular lenses in both
eyes. Posteriorly, the periphery and cup-to-disc ratios were
normal. Whitish/yellowish deposits on the macula were
visible, predominantly on the right side, but there was no
clear evidence of drusen or hemorrhage.
The next step was OCT imaging, which revealed evidence of retinal elevation overlying a discrete region of
September 2013 Retina Today 73
cover story
FAF is clearly a secondary tool,
but one that is invaluable because
it shows things that other
instrumentation does not.
Figure 2. FAF reveals hyperfluorescent subretinal deposits.
intense hyperreflective material with disruption of the
RPE and some suspicion of the presence of subretinal
fluid (Figure 1). However, the OCT images did not provide clear evidence of a neovascular process. We next
performed fluorescein angiography (FA), which showed
progressive staining of the lesion, but no clear evidence
of discrete leakage. Finally, I performed FAF, which
revealed an area of intense hyperfluorescent subretinal
deposits corresponding to the area of the widest lesion
on the fundus exam, characteristic of AVMD (Figure 2).
Definitive Diagnosis
AVMD is not an uncommon finding. In patients who
present with vision loss and macular lesions, OCT imaging will show accumulation of lipofuscin rich material
of unclear etiology, and FA will merely show progressive
staining of material. Although the OCT presentation was
highly suggestive of AVMD, the intense hyperfluorescence
seen in the subretinal deposit is typically only found in
retinal dystrophies, confirming the diagnosis of AVMD.
Current treatment for AVMD is observation. It is
crucial, however, to have a definitive diagnosis so that
patients are not given incorrect treatment. Anti-VEGF
has no impact on these lesions and is not indicated,
and treatment of AVMD with photodynamic therapy
has been associated with severe vision loss. This particular patient has been followed for 6 months and
remains stable.
OCT, FA, and FAF imaging were all performed with
the Spectralis (Heidelberg Engineering), which, in addi74 Retina Today September 2013
tion to having the luxury of multiple imaging modalities in the same system, offers a unique tracking feature.
The eye tracking system, called TruTrack, creates a
detailed retinal map each time a patient is imaged, and
this map is used to place follow-up scans in precisely
the same location as the baseline scan. This allows careful and precise comparisons of one slice of the retina
with the exact same slice from a previous visit. Without
it, judgment of progression of pathology can be somewhat of a guess.
Conclusion
FAF is clearly a secondary tool, but one that is invaluable because it shows things that other instrumentation does not. Published literature has shown FAF to be
useful in diagnostics, understanding pathophysiologic
mechanisms, phenotype-genotype correlation, identification of predictive markers for disease progression and
monitoring of novel therapies.1 Physicians who do not
have access to FAF must rely on clinical acumen to make
a diagnosis, or in cases where they are unsure, use fluorescein angiography. Overall, I find FAF to be an essential
feature that helps me to fully manage my patients. n
Karl G. Csaky is a vitreoretinal specialist with the Texas Retina Associates and is
the T. Boone Pickens Senior Scientist at the
Retina Foundation of the Southwest. Dr. Csaky
states that he is a consultant for Heidelberg
Engineering. Dr. Csaky can be reached at
[email protected].
1. Schmitz-Valckenberg S, Holz FG, Bird AC, Spaide RF. Fundus autofluorescence imaging: review and perspectives.
Retina. 2008;28(3):385-409.
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