A case series demonstrates the value of this new imaging modality.
BY MANISH NAGPAL, MS, DO, FRCS(Edin), and SHISHIR SHEKHAR SINGH, MS

Angiography is a photographic diagnostic examination tool used to assess
conditions of the retinal
vasculature. Conventional
angiography involves intravenous injection of a dye, either
fluorescein or indocyanine
green, into the vascular system. Its perfusion is then captured
with a camera. Although conventional angiography is a gold
standard imaging modality used to investigate many retinal
diseases, it is not without complications and side effects.
Optical coherence tomography (OCT) uses interferometricanalysis of short-coherence–length light to provide depthresolved imaging of ocular tissues such as the retina andchoroid. If multiple images are taken of the same area overtime, changes in reflectance properties over that area of tissue can be measured. Stationary tissue shows little variation,
whereas moving elements—blood flow for instance—show
more prominent changes.1 The variation over time of some ofthese measurable reflectance parameters (such as amplitude
or phase information of the reflected light) forms the basis fora flow imaging technique called OCT angiography (OCTA).
A COMPARISON
The basic concept of OCTA is motion detection. To isolate and image blood flow, we rely on the fact that blood is
the only thing in motion in the fundus. OCTA is therefore
a functional extension of OCT that can be used to visualize
the microvasculature by detecting motion contrast fromflowing blood.
Fluorescein angiography (FA) provides 2-D image sets thatallow dynamic visualization of blood flow with a wide fieldof view; patterns of dye leakage, pooling, and staining can beappreciated, and these have been well documented in theliterature.2 However, FA cannot separately visualize the intraretinal structures of major capillary networks; the images of

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OCT ANGIOGRAPHY IN
RETINAL AND CHOROIDALDISEASES
superficial and deep capillaries overlap, so two of the threemajor capillary networks (superficial retinal, deep retinal, andchoriocapillaries) do not appear to be imaged well despite
the retina’s being a nearly transparent structure.3
Other drawbacks that limit the widespread use of FA
include its invasive nature, its cost, and the time it takes toperform; therefore, it is not ideal for use on a regular basis
in a busy clinical setting. Although considered safe, the dyeposes risks ranging from nausea to allergic reactions, including, in rare instances, anaphylaxis. For evaluation of patientsrequiring frequent follow-up examinations or those who
may not tolerate injection of the intravenous dye, a rapid,
noninvasive technique to visualize retinal and choroidal
vessels would be beneficial.4
OCTA, in contrast, is a noninvasive technique that acquires
volumetric angiographic information without the use of adye. The en face images obtained can be scrolled to visualize
individual vascular plexuses and to segment the inner retina,
outer retina, choriocapillaris, and other areas of interest.4

AT A GLANCE• FA is an important diagnostic tool for evaluating
patients with retinal pathologies, but several
drawbacks limit its widespread use.
• OCTA is a noninvasive technique that does not
require the use of a dye; motion contrast due
to blood flow allows users to visualize the eye’s
microvasculature.
• OCTA is not without its own limitations, andvalidation of the accuracy and reproducibility of
OCTA data is needed.

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A

B

A

C

B

C

Figure 1. Fundus photograph OD shows lasered PDR (A).
FA of OD shows leaking microaneurysms (arrow) at theposterior pole with capillary nonperfusion (CNP) area adjacentto FAZ (B). OCTA of OD shows microaneurysms and CNP
area adjacent to FAZ corresponding to FA; note that the
microaneurysm formation (arrow) can be clearly delineatedand corresponds to leakage seen at same site in FA (C).

Figure 2. Fundus photograph OS shows ischemia in inferotemporal quadrant (A). FA of OS shows CNP area adjacentto FAZ and inferotemporal to it, surrounded by collateral
vessels (arrow) (B). OCTA of OS shows CNP area adjacentto FAZ and inferotemporal to it corresponding to FA; notethat the collateral vessel (arrow) can also be delineatedcorresponding to FA (C).

Furthermore, OCTA data can be viewed in 3-D form, retaining
the depth interrelationships of retinal and choroidal tissue.
In this article we share our experience using OCTA toimage a range of retinal vascular and choroidal diseases.

revealed lasered proliferative diabetic retinopathy (PDR)
changes OD (Figure 1A). FA showed leaking microaneurysms
OD (Figure 1B). OCTA revealed microaneurysms and capillary
nonperfusion (CNP) in the area adjacent to the foveal avascularzone (FAZ) OD (Figure 1C), corresponding with the FA image.
DR is one of the leading causes of blindness worldwide,and OCTA has already shown promise in identifying changes
in the disease.5 In this case, OCTA clearly visualized microaneurysms, locating their exact intraretinal depth, areas ofretinal nonperfusion, and FAZ remodeling. Thus, OCTA wasable to image retinal microvascular changes not detected byclinical examination. In cases that involve neovascularizationof the disc (NVD) and neovascularization elsewhere (NVE),
FA shows the leakage of dye from the neovascularization,
whereas OCTA can actually delineate the network of newvessels in NVD and NVE. Therefore OCTA may be clinicallyuseful in evaluating the microvascular status and effectiveness of treatments for DR.

CLINICAL CASE SERIESThis observational case series includes patients who presented to our practice. All patients were scanned with the
3 mm x 3 mm scan pattern using Angioscan OCTA software
for the RS-3000 Advance OCT system (Nidek).
Case No. 1: Patient With Diabetic Retinopathy andDiscussion
A 62-year-old man with diabetes and hypertension presented
with diminution of vision in his right eye (OD) lasting 3 years.
Ocular history included retinal laser performed on both eyesfor diabetic retinopathy (DR) 2 years previously. His best corrected visual acuity (BCVA) was 6/24 OD. Fundus examination
58 RETINA TODAY | NOVEMBER/DECEMBER 2016

B

A

B

C

D

C

D

Figure 3. Fundus photograph OS shows greyish elevation oftissue deep to retina at macula suggestive of CNV in AMD (A).
FA of OS shows a discrete, well-demarcated focal area ofhyperfluorescence at macula (arrow) in early phaseframe (B), with hyperfluorescence increasing in intensity inlater phase frame (C) and extending beyond boundaries ofhyperfluorescence identified in early phase, suggestive ofclassic CNV. The actual network of new vessels (arrow) can bevery clearly delineated in OCTA, and its size corresponds to theextent of leakage from CNV seen in FA (D).

Case No. 2: Patient With Retinal Vein Occlusion andDiscussion
A 65-year-old woman with known hypertension presented
for follow-up of resolving vitreous hemorrhage secondary to abranch retinal vein occlusion (BRVO) OD. She was asymptomatic in her left eye (OS). Her BCVA was 6/9 OD and 6/6 OS.
Fundus examination revealed ischemia in the inferotemporal
quadrant OS (Figure 2A), suggestive of inferotemporal BRVO. An
area of CNP adjacent to and inferotemporal to the FAZ OS wasshown on FA (Figure 2B). OCTA agreed with FA (Figure 2C).
In this case, OCTA findings were consistent with clinical,
anatomic, and FA findings, including areas of impaired
vascular perfusion, vascular dilation, shunt vessels (collaterals), and intraretinal edema. Hence, OCTA, in conjunction
with spectral-domain OCT, could be at least equally effective
as FA for evaluating and managing macular complications inpatients with RVO.
Case No. 3: Patient With Choroidal Neovascularization
and Discussion
A 72-year-old man, pseudophakic in both eyes (OU), presented with diminution of vision OS lasting 2 to 3 months. His

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A

Figure 4. Same patient as in Figure 3, 6 weeks after intravitreal
injection of ranibizumab OS. Fundus photograph OS shows
resolving CNV (A). FA of OS in early (B) and late (C) phasesshows an absence of the leakage from the CNV tissue comparedwith the pretreatment FA as seen in Figure 3 (B and C). The
actual network of new vessels seen in Figure 3D appears
to have disappeared in OCTA after intravitreal injection ofranibizumab (D).

BCVA was 6/24 OS. Fundus examination OS revealed grayish
elevation of tissue deep to the retina at the macula, suggestiveof choroidal neovascularization (CNV) in age-related maculardegeneration (AMD) (Figure 3A). On FA, a discrete, welldemarcated focal area of hyperfluorescence at the macula
was evident (Figure 3B), with hyperfluorescence increasing
in intensity and extending beyond boundaries identified inearly phase frames, suggesting classic CNV (Figure 3C). OCTA
distinctly showed the actual network of new CNV vessels(Figure 3D). The patient was given one intravitreal injection ofranibizumab 0.5 mg (Lucentis, Genentech) OS.
He presented 6 weeks later with an improvement in BCVA
to 6/12 OS. Fundus examination revealed resolving CNV
at the macula OS (Figure 4A). FA of the same eye in early(Figure 4B) and late (Figure 4C) phases showed an absenceof leakage from the CNV tissue compared with the pretreatment FA (Figures 3B and 3C). The network of new vessels
shown in Figure 3D was no longer visible on postinjection
OCTA (Figure 4D).
AMD is a leading cause of irreversible vision loss in those
65 years of age and older. AMD is broadly classified into wet
and dry forms. Wet AMD is heralded by the formation of
CNV; it accounts for approximately 15% of AMD cases andmakes up the majority of cases with vision loss.6
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El Ameen et al characterized CNV using OCTA.7 In
their cohort of 14 patients, all demonstrated a hyperflow
vascular lesion in the outer retina with a glomerulus (4 of
14 patients) or medusa head shape (10 of 14 patients),
surrounded by a dark halo, demonstrating that OCTA ishighly sensitive in detecting CNV.

A

B

C

D

EB

F

Figure 5. Fundus photograph OD shows a well-demarcatedoval-shaped area of neurosensory retinal detachment in theposterior pole with yellow dots seen over the posterior polesuggestive of CSCR (A). OCT scan OD shows fluid collection under
the neurosensory retina at the fovea with a small PED (B). FA of OD
shows inkblot pattern of leakage superonasal to fovea (arrow)suggestive of CSCR (C and D). OCTA with segmentation aroundthe ILM shows normal inner retinal vasculature (E). OCTA withsegmentation around the RPE shows fluid tract (arrow) corresponding to the site of inkblot leakage in FA and to the PED on OCT (F).

60 RETINA TODAY | NOVEMBER/DECEMBER 2016

Case No. 4: Patient with Central Serous
Chorioretinopathy and Discussion
A 39-year-old man presented with diminution of vision
OD for the past 3 to 4 years. His BCVA was 6/9 OD. Fundus
examination revealed a well-demarcated oval-shaped area ofneurosensory retinal detachment in the posterior pole withyellow dots over the posterior pole, suggestive of central
serous chorioretinopathy (CSCR) (Figure 5A). An OCT scanOD showed subneurosensory retinal fluid collection at the
fovea with a small retinal pigment epithelial detachment(PED) (Figure 5B). FA showed an inkblot pattern of leakage
superonasal to the fovea, suggestive of CSCR (Figures 5C
and 5D). With segmentation around the internal limiting
membrane (ILM), OCTA showed normal inner retinal vasculature (Figure 5E), whereas OCTA with segmentation aroundthe retinal pigment epithelium (RPE) showed a fluid tract(Figure 5F), corresponding to the site of the inkblot leakage
seen in FA and to the PED noted on OCT.
CSCR typically affects the young and middle-aged populations. Patients usually develop one small area or sometimes
several small areas of serous detachment of the RPE in themacular or paramacular area, generally associated withserous detachment of the overlying and surrounding retina.
Demonstration of CSCR is based on typical angiographic dyeleakage from the choroid into the subretinal space, associated with appearance of defects in the RPE and sometimes
pooling of dye in the sub–RPE space.
We report the OCTA feature of a probable fluid tract visible at the level of the outer retina corresponding to the siteof typical inkblot leakage on FA. Our case also had a small
PED at the same site as the fluid tract on OCTA; therefore,
it cannot be ascertained whether the leakage or the PED led
to the appearance of the fluid tract on OCTA. Hence, OCTA
images of the superficial and deep retinal plexus, outer retina,
and choriocapillaris did not reveal any characteristic pattern
directly associated with the leakage point in acute CSCR.
OCTA: LIMITATIONS AND FUTURE
APPLICATIONS
As indicated by the cases described above, OCTA has
major implications for understanding tissue perfusion, andthis imaging modality could help detect retinal blood flow
compromise before the appearance of clinically meaningfulchanges. OCTA can show both structural and blood flow
information, and it provides a detailed view of the retinal(Continued on page 64)

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vasculature, making it possible to accurately delineate microvascular abnormalities in patients with diabetic eye diseaseand vascular occlusions. Additionally, OCTA helps quantify
vascular compromise based on the severity of DR and canelucidate the presence of CNV in wet AMD.4
Although OCTA overcomes some of the limitations of conventional angiography (eg, invasiveness, allergic risk, and cost),
the technique is in its infancy, with plenty of room for improvement, so it has great potential. Unlike FA, OCTA is a static image.
It has a smaller field of view and lower resolution than FA.
Spaide et al described various artifacts seen in OCTA images,8 noting that these artifacts can occur due to OCT image
acquisition, intrinsic characteristics of the eye, eye motion,
image processing, and display strategies. Another limitation
is OCTA’s suboptimal correction of these artifacts. Because
OCTA uses the principle that movement in the back of theeye represents blood flow, it is prone to motion artifact.
Our expectations for OCTA must be tempered, given our
limited experience with the technology. As with any new technique, validation of the accuracy and reproducibility of thedata is needed. Further studies in larger cohorts are required
to establish an association between retinal flow compromise
and retinal pathologies. Additionally, future innovations inboth hardware and software technologies are expected tohelp in obtaining larger fields of view with higher resolution
and decreased motion artifacts. It seems likely that we aregoing to continue to hear about OCTA for a long time. n
1. Spaide RF. Volume-rendered angiographic and structural optical coherence tomography. Retina. 2015;35(11):2181-2187.
2. Witmer MT, Parlitsis G, Patel S, Kiss S. Comparison of ultra-widefield fluorescein angiography with the Heidelberg
Spectralis noncontact ultra-widefield module versus the Optos Optomap. Clin Ophthalmol. 2013;7:389-394.
3. Jia Y, Wei E, Wang X, et al. Optical coherence tomography angiography of optic disc perfusion in glaucoma. Ophthalmology. 2014;121(7):1322-1332.
4. Chalam KV, Sambhav K. Optical coherence tomography angiography in retinal diseases. J Ophthalmic Vis Res. 2016;
11(1):84-92.
5. Hwang TS, Jia Y, Gao SS, et al. Optical coherence tomography angiography features of diabetic retinopathy. Retina.
2015;35(11):2371-2376.
6. Age-Related Eye Disease Study Research Group. Risk factors associated with age-related macular degeneration. A
case-control study in the age-related eye disease study: Age-Related Eye Disease Study report number 3. Ophthalmology.
2000;107(12):2224-2232.
7. El Ameen A, Cohen SY, Semoun O, et al. Type 2 neovascularization secondary to age-related macular degeneration
imaged by optical coherence tomography angiography. Retina. 2015;35(1):2212-2218.
8. Spaide RF, Fujimoto JG, Waheed NK. Image artifacts in optical coherence tomography angiography. Retina.
2015;35(11):2163-2180.

Manish Nagpal MS, DO, FRCS(Edin)vitreoretinal consultant at the Retina Foundation in Ahmedabad,
Gujarat, Indian member of the Retina Today editorial advisory boardn financial interest: none acknowledgedn drmanishnagpal@yahoo.comnShishir Shekhar Singh, MSvitreoretinal consultant at the Retina Foundation in Ahmedabad,
Gujarat, Indian financial interest: none acknowledgedn shishirsingh123@yahoo.com
n64 RETINA TODAY | NOVEMBER/DECEMBER 2016