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OCT knowledge checker:
Identifying disease biomarkers:
How relevant is OCT-A?

Images provided by Richard Gale, York and Scarborough
Teaching Hospitals, NHS Foundation Trust

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This material has been developed for use on a desktop computer.

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OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography.
This promotional OCT knowledge checker is organised and funded by Bayer and is intended for UK healthcare professionals only.

The information provided in this presentation is according to the views of the author.

September 2023 | PP-EYL-GB-1907

Disclosures

Fees for:

Apellis, AbbVie, Alimera, Bayer, Biogen, Boehringer Ingelheim, Heidelberg, Novartis, Notal vision, Roche, Santen

Disclaimers

 

The case studies presented are from real patients and are used with permission.

Introduction to OCT-A (optical coherence tomography angiography)

  • OCT-A is a non-invasive imaging technique that utilises motion-contrast imaging and calculates differences in signal intensity between consecutive scans of the same ocular region to produce high-quality, cross-sectional scans of vascular flow
  • OCT-A can be used for the identification of choroidal neovascularisation (CNV) in a range of ocular pathologies
  • Although a useful diagnostic tool, OCT-A may be prone to imaging artefacts; therefore, an understanding of associated artefacts is essential to reduce the risk of misinterpretation and ensure accurate assessment of retinopathies
  • OCT-A imaging artefacts may include the following:
    • Distortion artefacts, caused by errors in image processing and display, or ocular motion
    • Shadow artefacts, caused by superficial retinal vessels and vitreous opacities (e.g. ocular floaters)
    • Projection artefacts, caused by interference from superficial vessels during imaging of deep tissue structures

Rodriguez FJ et al. Graefes Arch Clin Exp Ophthalmol 2018; 256 (11): 2019–2026.

Identifying OCT-A artefacts

Click on the top right image to identify the projection artefacts

The image presented is from a real patient.

BM, Bruch's membrane; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OS, oculus sinister (left eye); PAR, projection artefact removal.
Rodriguez FJ et al. Graefes Arch Clin Exp Ophthalmol 2018; 256 (11): 2019–2026. Image courtesy of author.

Identifying OCT-A artefacts

 

  • It is important to identify movement in CNV or macular neovascularisation (MNV) in neovascular age-related macular degeneration (nAMD)1
  • Pigment epithelial detachment (PED) and large drusen are often prominent in nAMD, and may be misinterpreted as new blood vessels on OCT-A1–3
  • In this instance, the en face image appears as if it is showing vascular flow; however, this is an example of a projection artefact1

The image presented is from a real patient.

BM, Bruch's membrane; CNV, choroidal neovascularisation; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OS, oculus sinister (left eye); PAR, projection artefact removal.
1. Information courtesy of author. 2. Karampelas M et al. Ophthalmol Ther 2020; 9 (4): 739–756. 3. Rodriguez FJ et al. Graefes Arch Clin Exp Ophthalmol 2018; 256 (11): 2019–2026. Image courtesy of author.

Identifying neovascularisation in nAMD (structural OCT)

 

  • The PED and hyperreflective material (HRM) seen in the structural OCT image are highly suggestive of CNV1

Is OCT-A needed to support this diagnosis?

  • The ATHENA study is a non-inferiority, prospective, randomised trial designed to understand the diagnostic accuracy of structural OCT with OCT-A, versus OCT with fundus fluorescein angiography (FA), for the identification of nAMD2
  • Results from the ATHENA trial will help understand whether OCT-A is necessary to support structural OCT in the diagnosis of nAMD2

The image presented is from a real patient.

ART, automatic real time; CNV, choroidal neovascularisation; IR, infrared; nAMD, neovascular age-related macular degeneration; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); PED, pigment epithelial detachment.
1. Information courtesy of author. 2. Niestrata M et al. Invest Ophthalmol Vis Sci 2022; 63 (7): 2902–F0055. Image courtesy of author.

Identifying neovascularisation in nAMD (OCT-A)

Click on the image to identify the OCT-A marker that denotes neovascularisation

The image presented is from a real patient.

ART, automatic real time; BM, Bruch's membrane; HR, high resolution; ILM, internal limiting membrane; IPL, inner plexiform layer; IR, infrared; nAMD, neovascular age-related macular degeneration; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); OPL, outer plexiform layer. Image courtesy of author.

Identifying neovascularisation in nAMD (OCT-A)

 

  • The white marker identified by the OCT-A represents vascular flow, which confirms the diagnosis of neovascularisation, as suggested by the structural OCT1
    • The ATHENA study will assess the importance of using OCT-A versus FA to confirm diagnosis made on OCT2
  • The white marker in this image is an example of a well-defined ‘medusa’ pattern; however, there are a variety of patterns identifiable through OCT-A that denote neovascular lesions, such as ‘seafan’ and ‘dead tree’ patterns3

The image presented is from a real patient.

ART, automatic real time; BM, Bruch's membrane; FA, fluorescein angiography; HR, high resolution; ILM, internal limiting membrane; IPL, inner plexiform layer; IR, infrared; nAMD, neovascular age-related macular degeneration; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); OPL, outer plexiform layer.
1. Information courtesy of author. 2. Niestrata M et al. Invest Ophthalmol Vis Sci 2022; 63 (7): 2902–F0055. 3. Ahmed M et al. Ann Med Surg 2021 70: 102826. Image courtesy of author.

Morphologic characteristics of neovascularisation using OCT-A

Click on the OCT-A image to identify the ‘dead tree’ pattern

The image presented is from a real patient.

BM, Bruch's membrane; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); PAR, projection artefact removal. Image courtesy of author.

Morphologic characteristics of neovascularisation using OCT-A

 

  • The pattern shown here is often referred to as a ‘dead tree’ pattern and is associated with chronic and inactive CNV or MNV1
  • The subretinal fluid (SRF) identified by the structural OCT supports this diagnosis of disease activity2

The image presented is from a real patient.

BM, Bruch's membrane; CNV, choroidal neovascularisation; MNV, macular neovascularisation; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); PAR, projection artefact removal.
1. Karacorlu M et al. Eye (Lond) 2019; 33 (8): 1280–1289. 2. Information courtesy of author. Image courtesy of author.

Implications of OCT-A patterns in nAMD

  • Although there are a variety of OCT-A patterns that can aid diagnosis of nAMD through the identification of neovascular lesions, these patterns are not always suitable as a guide for treatment criteria1,2
  • OCT biomarkers of nAMD, such as intraretinal fluid (IRF) and SRF, should be used to inform treatment decisions where possible3
    • A dye-based imaging technique such as FA may be considered in cases where OCT-A does not support presence of neovascularisation2,4

FA, fundus fluorescein angiography; nAMD, neovascular age-related macular degeneration; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; SRF, subretinal fluid.
1. Karacorlu M et al. Eye (Lond) 2019; 33 (8): 1280–1289. 2. Information courtesy of author. 3. Hanson RLW et al. Eye (Lond) 2022; 1–15; DOI: 10.1038/s41433–022–02360–4. 4. Soomro T et al. Eye (Lond) 2018; 32 (4): 661–672.

Nonexudative CNV

Click on the OCT-A image to identify the marker that denotes neovascularisation

The image presented is from a real patient.

BM, Bruch's membrane; CNV, choroidal neovascularisation; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); PAR, projection artefact removal. Image courtesy of author.

Nonexudative CNV

 

  • In this example, the structural OCT (bottom right) does not show any typical exudative features (e.g. IRF or SRF); however, the OCT-A pattern (top right) indicates presence of CNV1
    • This is an example of nonexudative CNV
  • Approximately 10% of eyes with nonexudative neovascularisation may become exudative within 1 year and may consequently require frequent monitoring of exudation2

The image presented is from a real patient.

BM, Bruch's membrane; CNV, choroidal neovascularisation; IRF, intraretinal fluid; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography; OD, oculus dexter (right eye); PAR, projection artefact removal; SRF, subretinal fluid.
1. Information courtesy of author. 2. Wang Y et al. Eye (Lond) 2023; 37 (10): 2048–2054. Image courtesy of author.

Key takeaways

  • It is important to understand the intricacies of OCT-A and associated artefacts prior to its implementation1
    • These may include distortion, shadow, or projection artefacts
  • The necessity of performing an OCT-A versus FA to confirm a diagnosis based on OCT disease biomarkers is being explored in the ATHENA study2
  • There are a range of OCT-A patterns that represent neovascularisation in nAMD, which may help with the diagnosis of nAMD, but are not always suitable as a guide for treatment criteria3,4
  • Eyes with nonexudative neovascularisation identified by OCT-A should be monitored due to a risk of becoming exudative5

FA, fluorescein angiography; nAMD, neovascular age-related macular degeneration; OCT, optical coherence tomography; OCT-A, optical coherence tomography angiography. 1. Rodriguez FJ et al. Graefes Arch Clin Exp Ophthalmol 2018; 256 (11): 2019–2026. 2. Niestrata M et al. Invest Ophthalmol Vis Sci 2022; 63 (7): 2902–F0055. 3. Karacorlu M et al. Eye (Lond) 2019; 33 (8): 1280–1289. 4. Information courtesy of author. 5. Wang Y et al. Eye (Lond) 2023; 37 (10): 2048–2054.

Thank you for completing this OCT knowledge checker

OCT, optical coherence tomography.

September 2023 | PP-EYL-GB-1907