As retina specialists turn more to optical coherence tomography angiography as a non-invasive alternative for high-resolution imaging of the choroid, the more uses they find for it. Association for Research in Vision and Ophthalmology 2016 devoted an entire track to OCT angiography. Here we report on a few of the innovative ways of using OCTA that ARVO researchers studied.

Of note were two comparative studies involving OCTA: one that evaluated OCTA against fluorescein angiography (FA) in detecting vascularization in diabetic retinopathy; and a second that looked at two different modalities of OCTA—ultra-high speed swept source (SS) and spectral domain (SD)—to visualize choroidal neovascularization (CNV) secondary to age-related macular degeneration.

OCTA vs. FA
In comparing OCTA and FA, researchers from Nagoya University School of Medicine in Japan wanted to get answers about how well OCTA can detect neovascularization and nonperfused areas in eyes with diabetic retinopathy.1 They performed both OCTA and FA on 34 eyes with diabetic retinopathy.

While they found that both methods yielded the same results in detecting neovascularization—1.9 ±4.0—OCTA actually had an advantage over FA in detecting capillary nonperfused areas: 2.9 ±1.9 vs. 2.2 ±1.8.

“Our findings show that OCT angiography can be used to evaluate the neovascularization and capillary nonperfused areas in eyes with diabetic retinopathy,” the investigators concluded. The study investigators had no disclosures.

SS vs. SD OCTA
A team of international investigators determined that SS-OCTA was able to image significantly larger areas of choroidal neovascularization more effectively than SD-OCTA.2

They evaluated 14 eyes in 13 patients and found markedly different measurements of CNV depending on what modality of OCTA they used. For 3 mm x 3 mm OCTA, the mean CNV area measured with SS-OCT was 0.949 ±1.168 mm2 vs. 0.340 ±0.301 mm2 with SD-OCT. For the 6 mm x 6 mm OCTA, the mean CNV areas were 1.218 ±1.218 mm2 and 0.604  ±0.592 mm2 for SS-OCTA and SD-OCTA, respectively.

“It is possible that SS-OCTA is better able to demarcate the full extent of CNV vasculature,” the investigators reported. Among the investigators’ disclosures were OptoVue and Carl Zeiss Meditec.

OCTAVE Study Results
In the poster session, OCTAVE study investigators reported on their efforts to compare CNV patterns in SD-OCTA, FA and indocyanine green angiography (ICGA) in exudative AMD.3 They used the following distinct morphologic parameters to characterize neovascular membranes on OCTA images: location; presence of a feeding vessel; presence of an anastomotic arcade; presence of an hypointense perilesional border; and caliber of the neovascular membrane. They also classified these parameters into five different patterns: tree; dead-tree; glomerular; lasso; and fragmented shapes. The primary endpoint was the description of each type of choroidal neovascularization morphology.

In 46 eyes of 43 patients with exudative AMD, OCTA clearly imaged the neovascular complex. The researchers observed types 1, 2 and 4 choroidal neovascularization in 34, 10 and two eyes, respectively, with the glomerular pattern being the most common (38 percent of type 1 CNV and 60 percent of type 2 [p<0.05]). In type 4 CNV, the “dead tree” pattern was noted in all eyes (p<0.05).

“This study did not identify any differences in OCTA between CNV types as defined by SD-OCT, FA and ICGA,” the investigators reported. “Microvascular structures can be delineated accurately and non-inva-
sively, suggesting that this approach provides a safer management of patients with exudative AMD.” The study investigators had no disclosures.

By ARVO 2017, we could see even more studies into the utility of OCTA, particularly SS OCTA, in evaluating and characterizing the retinal vasculature in diabetic retinopathy and AMD.  RS

REFERENCES
1. Ito Y, Iwase T, Yasuda S, et al. Comparisons of optical coherence tomography angiography and fluorescein angiography in detecting neovascularization and capillary nonperfused areas in eyes with diabetic retinopathy. Paper presented at the annual meeting of the Association for Research in Vision and Ophthalmology. May 1, 2016; Seattle, WA.
2. Louzada R, Novais E, Adhi M, et al.  Choroidal neovascularization analyzed on ultra-high speed swept source optical coherence tomography angiography compared to spectral domain optical coherence tomography angiography. Paper presented at the annual meeting of the Association for Research in Vision and Ophthalmology. May 1, 2016; Seattle, WA.
3. Espenan J, Gozlan J, Marchetti M, Boissonnot M,  Leveziel N. OCTAVE study: comparison of choroidal neovascularization patterns in optical coherence tomography angiography, fluorescein and indocyanine green angiography in age-related macular degeneration. Poster presented at Paper presented at the annual meeting of the Association for Research in Vision and Ophthalmology. May 1, 2016; Seattle, WA.