SD-OCT Angiography

OCT is an optical ranging and imaging technique first described in 1991 that has since been
used successfully to provide high-resolution, micrometer-scale depth imaging in clinical
ophthalmology (and other fields). It can be thought of as the optical analogue of ultrasound
imaging. For the ocular posterior segment, OCT provides rapid acquisition of high-resolution,
cross-sectional images of the retina that approximate tissue histology. In vivo imaging of
the retina with OCT has thus dramatically improved clinicians' diagnostic capabilities,
allowing earlier and more accurate diagnosis of disease and more precise assessment of
response to therapies over time.

While OCT provides important information on retinal anatomy, it is currently limited in its
ability to provide information on retinal vasculature and blood flow. Angiography is the
current gold-standard imaging modality for retinal vascular imaging. Angiography involves
intravenous injection of a fluorescent dye (typically either fluorescein or indocyanine green
for the retinal or choroidal vessels, respectively) that circulates through the body. A light
source emitting light at the specific excitation wavelength of the dye is placed in front of
the patient's eye, and a camera equipped with a filter corresponding to the emission
wavelength of the dye is then used to image vessel morphology and retinal perfusion, either
through still images or through a short movie. Angiography provides physiologic information
about the retina that complements the anatomical information provided by OCT. While generally
well tolerated by most patients, angiography does have drawbacks: it often requires the use
of a separate imaging system, it requires several minutes for image acquisition, and it
involves intravenous injection of a dye. Patients occasionally experience side effects of
intravenous dye administration, including nausea, discomfort, and rarely, anaphylaxis.

Several retinal imaging companies are developing the next generation of OCT technology: OCT
angiography (OCT-A). OCT-A allows noninvasive, high-resolution imaging of the
microvasculature of the retina and choroid (the vascular plexus subjacent to the retina),
without the need for intravenous dye administration. OCT-A platforms currently under
development include both spectral domain (SD) and swept-source (SS) based technologies.
Whereas SS-based OCT-A utilizes a longer wavelength (~1060 nm) light source, SD-based units
use the same light source used in commercially available and FDA-cleared OCT units on a
modified platform. Optovue, Inc. (Fremont, CA) has developed one such unit, a customized,
high-resolution SD-OCT system that implements a novel algorithm, the amplitude-based method
of split-spectrum amplitude-decorrelation angiography (SSADA) for OCT-A. This SSADA algorithm
allows for detection of motion in the blood vessel lumen by measuring the variation in
reflected OCT signal amplitude between consecutive cross-sectional scans. Optovue has
integrated the novel SSADA algorithm into their commercially approved RTVue SD-OCT unit for
their OCT-A unit, the AngioVue. The AngioVue can generate high-quality angiograms of both the
retina and choroid. Additionally, this refined method has produced images of the smallest
retinal vessels (capillaries) in normal healthy control participants. In this proposed
prospective interactive clinical study, we will use the AngioVue unit to image patients and
characterize vascular abnormalities that are present in the setting of retinal diseases.

Inclusion Criteria:

- Capable and willing to provide consent

- History of clinically diagnosed retinal diseases, including but not limited to
age-related macular degeneration, diabetic retinopathy, retinal vein occlusion,
macular telangiectasias, and diabetic macular edema

- At least 18 years of age

Exclusion Criteria:

- Unable or unwilling to give consent

- Under 18 years of age