Our goal as doctors is to prevent visual loss via earlier identification of disease, application of prophylactic medicine, and where necessary, earlier treatment. Using fundus autofluoresence (FAF) imaging along with spectral-domain optical coherence tomography (SD-OCT) with the Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany), we have been able detect early pathologies that are unable to be seen using other imaging methods. In this article, we present two pairs of siblings with type 2 ideopathic macular telangiectasia (IMT). There is an underlying genetic component to this disease, and with the SPECTRALIS, we are able to isolate several factors that clue us in to the presence of asymptomatic type 2 IMT.
CASE 1
A 42-year-old asymptomatic woman presented to us
with 20/20 vision. We classified the fluorescein angiogram
(FA) as normal; the blue laser fundus autofluoresence (FAF)
and SD-OCT also appeared normal when viewed separately.
When the FAF was compared to the corresponding SDOCT
scan, however, an anomaly was recognized (Figure 1).
Usually the foveal dip appears immediately after the area
that corresponds to the hyperreflective band (the little
bulge in the fovea seen in Figure 1). For our patient, however,
this was not the case. The thinnest part of the fovea,
rather, was temporal to where the anatomic fovea sits. After
running a volume scan we confirmed that the deepest
point of the fovea was not properly located (Figure 4).
So why were we taking FA, FAF, and OCTs for a patient with no apparent pathology? The patient's sister had a classic case of type 2 IMT. Although the patient was asymptomatic with 20/20 vision, we suspected that she had type 2 IMT without leakage due to the thinning temporal to the fovea. We found the Spectralis BluePeak blue laser autofluorescence (Heidelberg Engineering) as seen in Figure 2 to be helpful in making this diagnosis in the patient's sister. The confocal red-free imaging provides a markedly increased signal in a noninvasive manner that picks up any area of blue reflectance. FAF shows a maldistribution because of a depletion of luteal pigment, which is pathognomonic to type 2 IMT in the later stages.
CASE 2
In another set of siblings, we had similar findings. In
Figure 3, there is again displacement of the thinnest part
of the fovea, so there must be some atrophy, loss of cells,
or cytoplasmic volume in the neuroscensory retina. Had
we put this automatic volume scan over the deepest pit
we would not have picked this up. With the Spectralis,
however, the location of the fovea can be moved to
where it makes the most sense. The other angiographic
features of early type 2 IMT are seen in Figure 4; CBR
shows that there is abnormality. In the twin, the angiographic
findings show more advanced disease (Figure 5).
DISCUSSION
It is important to diagnose this disease as early as possible. Type 2 IMT is much more common than we previously
thought. It is probable that with standard imaging methods
we missed a large proportion of patients for whom we
could achieve better outcomes had we diagnosed them earlier.
In the Spectralis we have three components to improve
our diagnostics of this disease. SD-OCT allows us to see
thinning temporal to the fovea and FAF aids in the detection
of the loss of luteal pigment. Red-free imaging captures
increased reflectivity. As result, we can identify the disease
earlier before it becomes apparent on FA with the added
benefit of avoiding an invasive procedure.
In conclusion, the Spectralis is an important advance in achieving a better understanding of the genetic components type 2 IMT, both for earlier diagnosis and a better understanding of the disease itself.
Frank G. Holz, MD, is Chairman and Professor of Ophthalmology at the University of Bonn, Germany. He states that he is a consultant to Heidelberg Engineering. Dr. Holz can be reached via e-mail at frank.holz@ukb.uni-bonn.de.
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