Optical coherence tomography features of neovascularization in proliferative diabetic retinopathy: a systematic review

Abstract

Background Diabetic retinopathy (DR) is a leading cause of blindness due to diabetic macular edema (DME) or complications of proliferative diabetic retinopathy (PDR). Optical coherence tomography (OCT) is a noninvasive imaging technique well established for DME but less used to assess neovascularization in PDR. Developments in OCT imaging and the introduction of OCT angiography (OCTA) have shown significant potential in PDR. Objectives To describe the tomographic features of PDR, namely of neovascularization, both of the optic disc (NVD) and elsewhere (NVE), intraretinal microvascular abnormalities (IRMA), retinal nonperfusion areas (NPA), status of the posterior vitreous, vitreoschisis and vitreous and subhyaloid/sub-ILM hemorrhages. Data sources Electronic database search on PubMed and EMBASE, last run on December 19th 2019. Study eligibility criteria, participants and interventions Publications assessing OCT and/or OCTA findings in PDR patients. All study designs were allowed except for case-reports, conference proceedings and letters. Study appraisal Newcastle–Ottawa Scale for observational studies was used for purposes of risk of bias assessment. Results From the 1300 studies identified, 283 proceeded to full-text assessment and 60 were included in this comprehensive review. OCT was useful in detecting NVD and NVE, such as in characterizing disease activity and response to laser and/or anti-VEGF therapies. The absence of posterior vitreous detachment seemed determinant for neovascular growth, with the posterior hyaloid acting as a scaffold. OCTA allowed a more detailed characterization of the neovascular complexes, associated NPA and disease activity, allowing the quantification of neovessel area and flow index. However, changes in OCTA blood flow signal following local therapies did not necessarily correlate with structural regression. Widefield and ultra-widefield OCTA were highly sensitive in the detection of PDR, adding value to disease staging and monitoring. Compared to fluorescein angiography, OCTA was more sensitive in detecting microvascular changes indicating disease progression. Limitations Publication languages were restricted. Most included studies were observational and non-comparative. Risk of bias regarding case representativeness. Conclusions OCT-based retinal imaging technologies are advancing rapidly and the trend is to be noninvasive and wide-field. OCT has proven invaluable in diagnosing, staging and management of proliferative diabetic disease with daily application in clinical and surgical practices.

<p>Optical Coherence Tomography Angiography Features of Neovascularization in Proliferative Diabetic Retinopathy</p>

“…24,25 In PDR, OCTA can be useful to visualize retinal nonperfusion areas (NPAs) and the presence of blood flow in NVCs and IRMAs. 6,18,[26][27][28] Herein, we aim to describe features of neovascularization in PDR using OCTA, complementing previous observations. These findings have clinical utility in estimating the activity of specific neovascular complexes, monitoring treatment response, surgical planning, and reducing the need for dye-based imaging during busy clinics, all the more important now with the impact of the COVID-19 pandemic.…”

“…We 16 have previously tried to identify markers of neovascular activity using structural OCT alone before the advent of OCTA, but now OCTA renders the evaluation considerably simpler and the case presentations demonstrate its usefulness after treatment. 18,35,36 In the cases of NVCs without flow signal, all of which were NVDs, all had posterior shadowing. We hypothesize that this shadowing is related with loss of transmission from the fibrotic tissue proliferating associated with the NVD.…”

“…Previous studies [12][13][14][16][17][18] have shown that structural OCT is useful to observe the morphology of NVCs and their relationship with the adjacent tissue layers. It was also demonstrated that this technique can be useful to evaluate markers of neovascular activity.…”

“…OCT is used routinely in diabetic retinopathy to evaluate macular edema, [7][8][9][10][11] but can also be helpful in evaluating morphologic changes in PDR related to neovascularization. [12][13][14][15][16][17][18] With OCT, it is possible to evaluate neovascular complexes (NVCs) in their earliest stages and to identify associated vitreoretinal interface changes. 13,14,[16][17][18] Prior reports describe NVD as hyperreflective lesions over the optic disc with NVE appearing as flat vessels arising from the inner retina which then grow as hyperreflective loops.…”

“…[12][13][14][15][16][17][18] With OCT, it is possible to evaluate neovascular complexes (NVCs) in their earliest stages and to identify associated vitreoretinal interface changes. 13,14,[16][17][18] Prior reports describe NVD as hyperreflective lesions over the optic disc with NVE appearing as flat vessels arising from the inner retina which then grow as hyperreflective loops. 12,13,16,18 Also, NVCs can be differentiated from intraretinal microvascular abnormalities (IRMA) since the neovascularization breaches the internal limiting membrane (ILM) and grows into the posterior hyaloid.…”