9 Investigations
9.1 Corneal Topography and Tomography
9.2 Confocal Microscopy
9.3 Optical Coherence Tomography - Macula
9.4 Optical Coherence Tomography Angiography (OCT-A)
9.5 Optical Coherence Tomography - Glaucoma
9.6 Optical Coherence Tomography – Anterior Segment
9.7 Fundus Autofluorescence Imaging
9.8 Fundus Angiography - Fluorescein
9.9 Fundus Angiography - Indocyanine Green
9.10 B-scan Ultrasonography & UBM
9.11 Electrophysiology
9.12 Automated Visual Fields
9.13 Neuroimaging
9.4 Optical Coherence Tomography Angiography (OCT-A)
Optical coherence tomography angiography (OCT-A) has emerged as a non-invasive technique for imaging the microvasculature of the retina and the choroid. It utilises laser light reflectance off the surface of moving red blood cells to accurately depict vessels through different segments, thus eliminating the need for intravascular dyes. OCT-A produces images that can be segmented into different levels, e.g.: the superficial retinal plexus, the deep retinal plexus, the outer retina and the choriocapillaris.
The main advantages of OCT-A over conventional fluorescein angiography include its non-invasiveness and the shorter acquisition times. Limitations include artefacts such as projection artefact.
In OCT-A, diseases manifest as the abnormal presence of flow (neovascularisation), anomalous vessel geometry (dilated vessels, aneurysms) or the absence of flow (non-perfusion/capillary dropout). It does not visualise leakage or polyps accurately.
Clinical Applications
OCT-A is increasingly being utilised to assess retinal and optic nerve disorders.
- Diabetic retinopathy – identifying the foveal avascular zone, microaneurysms and neovascular complexes
- CNV analysis in age-related macular degeneration, central serous chorioretinopathy, myopic CNV, macular telangiectasia and uveitic CNV
- Vascular occlusions – evaluation of nonperfused areas and the integrity of the superficial and deep plexus. The preservation of the deep vasculature has been associated with better visual outcomes
- Glaucoma – may enable pre-perimetric detection of glaucomatous damage by assessing for attenuated peripapillary and macular vessel density.
- Differentiating papilledema from disc drusen
-neovascularisation-secondary-to-central-serous-chorioretinopathy.jpg)
All rights reserved. No part of this publication which includes all images and diagrams may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the authors, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law.
Vitreoretinal Surgery Online
This open-source textbook provides step-by-step instructions for the full spectrum of vitreoretinal surgical procedures. An international collaboration from over 90 authors worldwide, this text is rich in high quality videos and illustrations.
