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Anterior segment optical coherence tomography angiography for iris vasculature in pigmented eyes
  1. Marcus Ang1,2,3,
  2. Kavya Devarajan2,
  3. Anna CS Tan1,2,3,
  4. Mengyuan Ke2,
  5. Bingyao Tan2,5,6,
  6. Kaiying Teo2,
  7. Chelvin C.A. Sng2,4,
  8. Daniel S Ting1,2,3,
  9. Leopold Schmetterer1,2,3,5,6,7,8,9
  1. 1 Singapore National Eye Centre, Singapore
  2. 2 Singapore Eye Research Institute, The Academia, Singapore
  3. 3 Department of Ophthalmology and Visual Science, Duke-NUS Graduate Medical School, Singapore
  4. 4 Department of Ophthalmology, National University Health System, Singapore
  5. 5 SERI-NTU Advanced Ocular Engineering (STANCE), Singapore
  6. 6 Institute for Health Technologies, Nanyang Technological University, Singapore
  7. 7 Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria
  8. 8 Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
  9. 9 Institute of Clinical and Experimental Ophthalmology, Basel, Switzerland
  1. Correspondence to Marcus Ang, Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore; marcus.ang{at}snec.com.sg

Abstract

Purpose To compare anterior segment optical coherence tomography angiography (AS-OCTA) systems in delineating normal iris vessels and iris neovascularisation (NVI) in eyes with pigmented irides.

Methods Prospective study from January 2019 to June 2019 of 10 consecutive patients with normal pigmented iris, had AS-OCTA scans with a described illumination technique, before using the same protocol in five eyes with NVI (clinical stages 1–3). All scans were sequentially performed using a spectral-domain OCTA (SD-OCTA), and a swept-source OCTA (SS-OCTA, Plex Elite 9000). Images were graded by two masked observers for visibility, artefacts and NVI characteristics. The main outcome measure was iris vessel density measurements comparing SS-OCTA and SD-OCTA systems.

Results The median age of subjects was 28 (20–35) years, and 50% were female. The paired mean difference of iris vessel density measurements was 11.7 (95% CI 14.7 to 8.1; p=0.002), SS-OCTA detecting more vessels than SD-OCTA. The inter-rater reliability for artefact score (κ=0.799, p<0.001) and visibility score (κ=0.722; p<0.001) were substantial. Both AS-OCTA systems were able to detect NVI vessels with a fair agreement (κ=0.588), with clearer NVI characteristics in stage 1/2 compared to stage 3 NVI (mean difference NVI score: 2.7±0.4, p=0.009).

Conclusion The SS-OCTA was better able to delineate iris vessels in normal pigmented irides compared to SD-OCTA. Both AS-OCTA systems identified NVI characteristics based on its atypical configuration or location, but further improvements are needed to allow for more accurate objective, serial quantification for clinical use.

  • Iris
  • Imaging

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Footnotes

  • Funding This work was supported by Singapore National Eye Centre Health Research Education Fund, National Medical Research Council (grants CG/C010A/2017, OFLCG/004C/2018 and TA/MOH-000249-00/2018.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant and available to the study have been included in the article.

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