IMAGINGPANORAMIC IMAGING
WITH OCTA
Thanks to a large field of view, panoramic imaging software can noninvasively display
retinal features similar to those seen with dye-based angiography.
BY MANISH NAGPAL, MS, DO, FRCS(Edin), and RAKESH JUNEJA, MS

Optical coherence tomography (OCT) and fluorescein angiography (FA) are
the two most commonly
employed imaging tools toinvestigate clinical featuresand plan management forvarious retinal pathologies.
Whereas OCT allows morphologic and quantitative assessments, FA detects anatomic locations and leakage patterns.
In certain conditions, either imaging mode can lead todiscrepancies in the data yielded, and neither can provide
details of deeper retinal capillary plexus or choroidal vasculature. These limitations significantly affect our ability tounderstand pathology and, consequently, determine prognosis and management.1
THE SKINNY ON OCTA
OCT angiography (OCTA) is a functional extension of
OCT that works on the principle of decorrelation. It uses
interferometric analysis of short-coherence-length lightreflected from moving blood within the retina and choroid

AT A GLANCE• OCTA software can scan a limited field of view invarious sizes of cube based on examiner preference
and on the location and size of pathology.
• Panoramic OCTA can mimic the findings of
FA noninvasively and replicate them on eachfollow-up exam.
• Panoramic OCTA has enabled clinicians to replace
FA and ICGA in certain situations, such as whencontraindications exist, but further investigation isneeded.

2 RETINA TODAY | APRIL 2017“

OCT angiography (OCTA) is afunctional extension of OCT
that works on the principleof decorrelation.

and calculates the variation over time of reflectanceparameters (eg, amplitude or phase).2 OCTA can generate
3-D maps of microvasculature flow pattern from retinal
capillary plexus and choroidal vasculature, and its capabilities have enabled us to better understand, analyze, andtreat a number of retinal pathologies.3,4OCTA imaging software generates images based on a voxelby-voxel computation of decorrelation signal.5 In a chosen
field of view, the software scans 256 voxels, with eight B-scans
repeated at each voxel. Further, at each voxel the software
performs 256 A-scans per B-scan, with a distance between
B-scans of 10 μm. The number of B-scans performed per voxel
and the number of A-scans per B-scan varies according to thesoftware and the algorithm used. Algorithms incorporated
into the software perform computations based on clusters of
B-scans and generate flow patterns based on motion of erythrocytes within the vasculature. This results in the formationof en face images of retinal capillary network and choroidal
vasculature at various levels.6,7
Limits of Resolution
OCTA software can scan only a limited field of view invarious sizes of cube based on examiner preference and on
the location and size of pathology. The fields of view usedmost frequently are 3 mm by 3 mm and 6 mm by 6 mm.

Expanding the Field of View
The AngioScan OCT Angiography software on the
RS-3000 Advance OCT (Nidek) allows clinicians to compose
panoramic images with larger fields of view—12 x 9 mm,
9 x 9 mm, 6 x 6 mm, and 4.5 x 4.5 mm—providing, respectively, 40° x 30°, 30° x 30°, 20° x 20°, and 15° x 15° fields ofview. In each of these sizes of fields of view, the software
splits the scanning area into 3 mm by 3 mm cubes. The resolution obtained is therefore the same as that of an individual
3 x 3–mm cube provided by other software, but a larger
field is simultaneously scanned at the same time.
The en face images obtained with OCTA allow clinicians
to visualize individual retinal vascular plexuses and choriocapillaris.2 The large fields of view provided by panoramic
imaging software now enabled us to noninvasively capturefeatures previously seen only with FA. Further, panoramic
OCTA images offer several advantages over dye-based
angiography, including being noninvasive, allowing 3-D
analysis, and being repeatable on follow-up examinations.5
This article explores some of the uses of panoramic
imaging software by comparing AngioScan OCT
A

A

B

C

D

IMAGING

In general, the smaller the size of the cube, the higher the
resolution. Thus, a limitation of OCTA is decreased image
resolution with larger fields of view.

Figure 2. Fundus examination OS shows pale disc, lasered
proliferative DR, and fibrous proliferation, causing traction
threatening to involve the macula (A). SD-OCT OS shows
altered foveal contour, cystoid spaces, and hard exudates,with CFT measuring 466 µm (B). FA OS shows altered FAZ,
microaneurysms, NVD, NVE, and capillary nonperfusionareas at the posterior pole (C). 12-x-9-mm panoramic OCTA
OS shows altered FAZ, which was obscured in FA, and awell-defined pattern and architectures of NVD and NVE at theposterior pole, signifying neovascularization and corresponding capillary nonperfusion areas at the posterior pole (D).

B
Angiography panoramic images with traditional FA images
in a series of case reports.

CC

Figure 1. Fundus examination OD shows hemorrhage at theposterior pole and a few laser marks superotemporal to the
FAZ (A). SD-OCT OD shows altered foveal contour with ERM
and central foveal thickness (CFT) measuring 261 µm (B). FA
OD shows normal FAZ, NVE around 1 DD temporal to the FAZ,
focal leakage 0.5 DD inferonasal to the disc, and staining fromlaser marks (C). 12-x-9-mm panoramic OCTA OD shows a normal FAZ with well-demarcated architecture of vessels under
the NVE (seen as leakage on FA) present 1 DD temporal to the
FAZ and 0.5 DD inferonasal to the disc.

OCTA PANORAMIC IMAGING VS. FA
The following is an observational case series of patients
who presented at our practice. All patients were scanned
using the AngioScan OCT Angiography software on the
RS-3000 Advance OCT.
Case No. 1
A 55-year-old man with known hypertension presented
with decreased visual acuity in his right eye (OD) lasting
2 months. His BCVA was 6/9 OD with early cataractous
changes. Fundus examination revealed hemorrhage at theposterior pole around 1 disc diameter (DD) temporal to
the foveal avascular zone (FAZ) and 0.5 DD inferonasal
to the disc and laser marks superotemporal to the FAZ(Figure 1). Spectral-domain OCT (SD-OCT) showed analtered foveal contour OD and an epiretinal membrane(ERM), with central foveal thickness measuring 261 μm. FA
revealed a normal FAZ OD, areas of leakage suggestive of
neovascularization elsewhere (NVE) around 1 DD temporalto the FAZ, focal leakage 0.5 DD inferonasal to the disc,and staining from laser marks.
Panoramic OCTA with a 12-x-9-mm field of view
APRIL 2017 | RETINA TODAY 3

IMAGING

A

B

A

B

C

D

C

D

Figure 3. Fundus examination OD shows sclerosed bloodvessels, laser marks, and collateral vessels (A). SD-OCT
OD shows a maintained foveal contour with ERM and CFT
measuring 238 µm (B). FA OD shows altered FAZ, staining oflaser marks, and collateral vessels present superotemporal to
the FAZ (C). 12-x-9-mm panoramic OCTA OD corresponding
to FA shows altered FAZ with well demarcated architecture ofcollateral vessels present superotemporal to the FAZ (D).

showed a normal FAZ, with well-demarcated architectureof vessels under the NVE (seen as leakage on FA) present
1 DD temporal to the FAZ and 0.5 DD inferonasal to thedisc OD.
Case No. 2
A 48-year-old woman with known diabetes andhypertension presented with decreased visual acuity in
her left eye (OS) lasting 4 months. Her BCVA was 6/9 OSwith cataractous changes. Lasered proliferative diabetic
retinopathy, a pale disc, and traction threatening themacula were noted on fundus examination OS (Figure2). SD-OCT revealed altered foveal contour, cystoid
spaces, and hard exudates, with central foveal thickness
measuring 466 μm OS. FA revealed an altered FAZ, microaneurysms, neovascularization at the disc (NVD), NVE,
and capillary nonperfusion at the posterior pole OS.
Panoramic OCTA with a 12-x-9-mm field of view OS
showed a slightly altered FAZ, which was obscured on
FA, and a well-defined pattern and architecture of NVD
and NVE at the posterior pole, signifying neovascularization and capillary nonperfusion areas inferotemporal to
the FAZ.
Case No. 3
A 56-year-old woman who was known to have hypertension presented with decreased visual acuity OD
lasting 2 months. Her BCVA was 6/9 OD with early
4 RETINA TODAY | APRIL 2017

Figure 4. Fundus examination OD shows sclerosed bloodvessels, laser marks, and collateral vessels near the macula(A). SD-OCT OD shows normal foveal contour, corrugationof inner retinal layers, and CFT measuring 238 µm (B).
FA OD shows a normal FAZ, staining of laser marks, andcollateral vessels present in the posterior pole near theFAZ (C). 12-x-9-mm panoramic OCTA OD corresponding to
FA revealed a normal FAZ, clearly demarcated architectureof collateral vessels in the posterior pole near the FAZ, anda few laser marks inferiorly just below the arcade (D).

cataractous changes. Fundus examination revealedsclerosed blood vessels and laser marks with collateral
vessels OD (Figure 3). SD-OCT revealed a maintained
foveal contour and ERM with central foveal thickness
measuring 238 μm OD. FA revealed altered FAZ, staining
from laser marks, and collateral vessels present superotemporal to the FAZ OD.
Panoramic OCTA with a 12-x-9-mm field of view
showed the altered FAZ and clearly demarcated architecture of collateral vessels present superotemporal to
the FAZ OD.
Case No. 4
A 28-year-old man presented with decreased visualacuity OD lasting 2 months. His BCVA was 6/9 OD, andfundus examination revealed sclerosed blood vessels andlaser marks with collateral vessels near the macula OD(Figure 4). SD-OCT revealed normal foveal contour, corrugation of inner retinal layers, and central foveal thickness
measuring 238 μm OD. FA revealed a normal FAZ, staining
from laser marks, and collateral vessels present in theposterior pole near the FAZ OD.
Panoramic OCTA with a 12-x-9-mm field of view
showed a normal FAZ, clearly demarcated architecture ofcollateral vessels in the posterior pole near the FAZ, and a
few laser marks inferiorly just below the arcade OD.

B

C

D

Figure 5. Fundus examination OS before treatment at the timeof presentation reveals a subretinal yellowish scar at the
fovea (A). SD-OCT OS before treatment at the time of presentation shows normal foveal contour, altered photoreceptor layer,
a small pigment epithelial detachment (PED), and subfoveal
and juxtafoveal scarring, with CFT measuring 188 µm (B). FA
OS prior to treatment at presentation shows an altered FAZ
and a hypofluorescent area in the foveal and juxtafoveal areas
in early phase, which became hyperfluorescent in late phase,suggesting active choroiditis (C). 12-x-9-mm panoramic OCTA
OS before treatment at presentation shows a normal FAZ anda normal retinal capillary plexus from superficial to avasculararea. Choroidal vasculature shows an area of large flow voidand masking of the normal choroidal architecture pattern at
the level of the RPE and Bruch membrane, suggesting choriocapillaris hypoperfusion (D).

Case No. 5
A 29-year-old man presented with decreased visualacuity OS lasting 1 month. His BCVA was 6/12 OS. A
subretinal yellowish scar at the fovea was noted on fundus examination (Figure 5). SD-OCT showed a normal
foveal contour, an altered photoreceptor layer, a small
pigment epithelial detachment (PED), and subfoveal andjuxtafoveal scarring, with central foveal thickness measuring 188 μm OS. FA revealed an altered FAZ and a hypofluorescent area in the foveal and juxtafoveal areas OS inearly phase, which became hyperfluorescent in late phase,suggesting active choroiditis.
Panoramic OCTA with a 12-x-9-mm field of view
showed a normal FAZ OS and a normal retinal capillary
plexus from superficial to avascular area. Choroidal
vasculature showed an area of large flow void andmasking of the normal choroidal architecture patternat the level of the retinal pigment epithelium (RPE)
and Bruch membrane, suggesting choriocapillaris
hypoperfusion.
The patient was treated with a course of intravenous

methylprednisolone for 3 days under physician supervision. He was also given a tapering course of oral steroids
and was seen again 1 month later. His BCVA after treatment was 6/9 OS. A decrease in the size of the subretinal
yellowish scar at the fovea was noted on fundus examination (Figure 6). SD-OCT showed a normal foveal contour
OS, an altered photoreceptor layer, a small PED, subfoveal
and juxtafoveal scarring, and central foveal thickness
measuring 188 μm.
Panoramic OCTA with a 12-x-9-mm field of view showeda normal FAZ OS and normal retinal capillary plexus fromsuperficial to avascular area. Choroidal vasculature now
showed a decreased area of large flow void and unmaskingof the normal small and large choroidal architecture pattern at the level of RPE-Bruch membrane, which suggested
choriocapillaris reperfusion.
DISCUSSION
FA is considered the gold standard of imaging and is
widely used in the diagnosis and management of a varietyof ocular disorders.8-11 FA provides information on theretinal vasculature, limited only to the superficial capillary
plexus, and it lacks penetration to the choroid, thus providing no details of the choroidal vasculature.4 Indocyanine
green angiography (ICGA) complements FA because it has
A

BC

Figure 6. Fundus examination OS, after treatment showsa decrease in the size of the subretinal yellowish scar at
the fovea (A). SD-OCT OS after treatment shows a normal
foveal contour OS, an altered photoreceptor layer, a small
PED, subfoveal and juxtafoveal scarring, and CFT measuring
188 μm (B). 12-x-9-mm panoramic OCTA OS after treatmentshows a normal FAZ and normal retinal capillary plexus fromsuperficial to avascular area. Choroidal vasculature now
shows a decreased area of large flow void and unmaskingof the normal small and large choroidal architecture patternat the level of RPE-Bruch membrane, which suggests
choriocapillaris reperfusion (C).

APRIL 2017 | RETINA TODAY 5

IMAGINGAIMAGING“

With the advent of panoramic
imaging, OCTA can now mimic
the findings of FA and replicate
these on each follow-up exam
noninvasively.

the ability to penetrate the choroid and it shows details ofchoroidal vascular pathologies.
Conventional dye-based angiography, including FA and
ICGA, has some disadvantages; it is invasive, it requires
intravenous dye injections, and it can cause side effects
including extravasation, nausea, vasovagal reaction, andanaphylaxis. Conventional angiography also carries systemic risks, and it is expensive, time-consuming, andresource-intensive. Additionally, FA is contraindicated in
pregnant women, in children, and in patients with renal
or cardiac disorders. Repeatability is a major concern
because of the invasive nature of injection-based angiography; hence, follow-up examination is difficult.12-17
OCTA is a revolutionary imaging modality that can
detect retinal and choroidal blood flow compromise
before the appearance of clinically meaningful changes.
OCTA enables imaging of the retinal and choroidal
vascular structure by detecting the reflectance phase andamplitude variation of blood flow over time to distinguish vessels from static tissue.18,19 It has thus provided
us with new insights to better understand and manage
retinal and choroidal pathologies.
With the advent of panoramic imaging, OCTA can
now mimic the findings of FA and replicate these on eachfollow-up exam noninvasively. Although OCTA surpasses
certain limitations of conventional angiography, this imaging modality is still in its infancy, and there is room fortechnical refinement. During the process of image acquisition, artifacts can occur due to eye movement, tremor,
circardian rhythm, breathing, and image processing. Theselimitations should diminish as the technology is refined.
A PLACE FOR PANORAMIC OCTA?
Panoramic OCTA imaging is a unique tool that canreplicate the findings of conventional angiography noninvasively. Panoramic OCTA can even replace FA and ICGA
6 RETINA TODAY | APRIL 2017in certain situations, such as in patients with contraindications to dye injections or side effects from previous examinations, and for follow-up examinations. Because it is anacent technology, experience is still limited.
Prospective, longitudinal studies with larger cohorts are
required to validate the accuracy of results and reproducibility of data generated to date. In the near future, withadvances in medical engineering and further upgrades tosoftware and technology, we hope to benefit from imaging
software that can provide images with high resolution andmuch larger fields of view. Nonetheless, panoramic OCTA
is certainly a promising imaging modality that is likely toplay a part in the future of retinal imaging. n
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Manish Nagpal, MS, DO, FRCS(Edin)v itreoretinal consultant at the Retina Foundation in
Ahmedabad, Indian financial disclosure: consultant to Nidekn member of the Retina Today editorial advisory boardn drmanishnagpal@yahoo.com
nRakesh Juneja, MSv itreoretinal fellow at the Retina Foundation in Ahmedabad, India
financial interest: none acknowledgedn dr_rakeshjuneja555@yahoo.com
nn