Incorporating OCT Angiography Into Patient Care

Transcription

1 Incorporating OCT Angiography Into Patient Care Beth A. Steele, OD, FAAO OCT A: Introduction Isolates microvascular circulation from OCT image data Axial resolution = 5 microns (i.e. fine capillaries visible) Visualization of blood flow in the retina Blood flow = areas of perfused blood vessels are bright No flow or too slow to detect = dark Non invasive Images can be broken down into anatomical layers for analysis 1. Vitreo retinal interface 2. Superficial retina 3. Deep retina 4. Avascular outer retina 5. Choroid Superficial Inner Deep Inner Avascular Outer Choroid Instrumentation and Practical Considerations 3 Dimentional Data on Depth! Instrumentation AngioVue (Optovue) SS OCT angio (Topcon) Spectralis (Heidelberg Engineering) AngioPlex (Zeiss Meditec) Angioscan (Nidek) Additional cost for technology No separate billing codes ; no separate reimbursement Isolates blood flow information at a specific retinal depth Vs. IVFA images are 2 dimensional Can be teased out after image acquisition Various disease etiologies different retinal depths E.g. wet age related macular degeneration: CNVM at level of the RPE E.g. RVO: neo very superficial (pre retinal) E.g. PDR: neo very superficial (pre retinal) JAMA 2015

2 PDR Clinical Applications Superficial scan: shows ischemia and NV Pre retinal scan. Confirms location of new vessel Early/more detailed representation of vascular retinal lesions e.g. microaneursyms, telangiectasia More careful follow up, aggressive recommendations Can easily repeat to monitor condition s progress e.g. treat CNVM until no flow May reduce need for referral Nghiem Buffet S, Ayrault S, Delahaye Mazza, C. Practical OCT Angiography. Carl Zeiss Meditech. OCT A Compared to FA and ICG FA and ICG still gold standards Shows good agreement with FA in visualizing areas of ischemia OCTA: flow information at a fixed point in time OCTA is more prone to artifact than FA or ICGA OCTA can also miss areas of slow blood flow such as in microaneurysms or fibrotic CNV not able to image leakage, staining, pooling, or vessel filling time BUT: with an FA, retinal pathology can be obscured by this leakage as well as hemorrhage or media opacities, and localization of the depth of the lesion and size delineation of neovascularization can be difficult due to dye leakage Limitations 9mm cube limits area of evaluation small FOV media opacities OCTA image will appear dark dense retinal pigment / hemorrhages can obstruct light from reaching deeper layers. projection artifacts some software corrects for this Due to fluctuating shadows cast by blood flow in superficial layer onto deeper layers occur in reflective retinal layers (e.g. RPE) can lead to false positives on deeper retinal layer analysis areas of slow flow appear dark segmentation errors Image based corresponding slab: upper and lower boundaries are defined by segmentation lines errors in segmentation will cause the en face angiogram to be displayed incorrectly

3 Classic CNVM Wet AMD Scan below RPE with projection artifact here retinal vasculature plus new vessel superimposed Nghiem Buffet S, Ayrault S, Delahaye Mazza, C. Practical OCT Angiography. Carl Zeiss Meditech. Projection artifacts with PED Simulates blood flow. Actually reflectance of inner retinal vasculature on the edges of the PED How Can OCT A Impact Patient Care? Focusing on highlighted conditions. Louzada R, Et al. Can J Ophth Aug 2017

4 Wet AMD Earlier, non invasive detection for both: 1. Classic CNVM above RPE 2. Occult CNVM under RPE with high risk of future leakage often w/o symptoms at first Better data for location Full depth color encoded image Deep scan revealing CNVM below the RPE Superficial Retinal Layer over FA B Scan from OCT RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES 2017 Intravitreal aflibercept injections are associated with a significant change in native retinal and choroidal vasculature. Moreover, the treatment did not cause a reduction in lesion area, but rather reduced the flow in the choroidal neovascularization. Zeiss.com Diabetic Retinopathy Macular Telegiectasia Earlier clinical findings.. microaneurysms capillary nonperfusion small pockets of ischemia seem to be visualized better on OCTA than FA. foveal avascular zone (FAZ) Full depth color encoded image Superficial Retinal Layer Superficial layer overlaid onto FA Deep Retinal Layer Zeiss.com Nghiem Buffet S, Ayrault S, Delahaye Mazza, C. Practical OCT Angiography. Carl Zeiss Meditech.

5 BRVO / CRVO location of the occlusion areas of ischemia Ischemic vs. nonischemic subtle microvascular abnormalities Some additional / different data compared to FA Complimentary to the FA Zeiss.com Full depth : 6x6 Full depth : 3x3 20/400 OD Extensive vascular history

6 NAION OCT A of Normal Optic Nerve OCT A of Ischmemic Optic Neuropathy What Other Questions Exist? Selected examples from the literature.

7 Glaucoma Leber s Hereditary Optic Neuropathy Many, many others Focus is on Vessel Density (VD) around ONH Optic disc perfusion / blood flow Vessel density changes preceded changes in RNFL ; mirrored changes in GCL Retinal Capillary Hemangioblastoma Unexplained Pallor Depth of vascular features of tumors noted with OCT A Smaller tumors better differentiated with OCT A due to absence of leakage 63 AAF with history HIV, HTN, stroke, cancer, kidney disease VA 5/600 +APD BP 200/120

8 OD pallor Superficial Deep Full depth color encoded image OS healthy Deep scan revealing CNVM below the RPE B Scan from OCT

9 In Summary We are still learning what OCT A has to offer Earlier detection New diagnosis / management strategies Complimentary to other standards, and often additional information compared to standards Awareness of limitations is crucial