Dr Alan Burrow
DipOptom FBOA (HD) DCLP DOrth FBCO MSC (Med) GCOT MOptom GCBA
Age-related macular degeneration is the major cause of severe visual loss in older adults1 with approximately 10 to 15 per cent associated with a neo-vascular form of the disease resulting in severe visual loss.2
Traditionally, this condition has been further classified according to histopathology with type 1 presenting with a choroidal neovascular membrane (CNV) between Bruch’s membrane and the retinal pigment epithelium (RPE) and type 2 with the CNV in the retina above the RPE.3
This classification has been largely dependent on angiographic patterns of fluorescence using the invasive techniques of systemic injection of either fluorescein or less frequently, indocyanine green and tracking the flow photographically through the retinal vasculature.3
The advent of ocular coherence tomography (OCT) provides a valuable, non-invasive method of detecting structural changes commonly associated with CNV but without the ability to observe the vascular changes.3
The recent release of commercial OCT angiography enables observation of vascular changes non-invasively in vivo at different levels within the retina without the limitations associated with the dynamics of the dye.4,5
The Optovue XR-Avanti OCT Angiovue software utilises a high-speed (70,000 axial scans per second) spectral domain (SD) OCT platform with amplitude decorrelation to assess blood flow through the superficial and deep capillary retinal plexuses, outer retina and choroid capillary layer.4,6
Numerous authors have highlighted the benefits of OCT angiography when compared with fluorescein and indocyanine green techniques.6,7,8,9,10,11 In exudative macular degeneration, changes in the normally avascular outer retina and vascular choroid capillary layer are of primary interest.
Figure 1. Long-standing pigmentary change in the para foveal area (Dec 2015)
Figure 2. Increased area of depigmentation and macular oedema (March 2016)
A 75-year-old symptom-free Caucasian male presented in December 2015 for a routine optometric examination. Corrected acuities were right and left 6/5 with normal intraocular pressures of right and left 15 mmHg. There was a small area of depigmentation infero-temporally to the fovea as well as a large peripapillary scar, both of which had been present since at least 2008 (Figure 1). The left fundus was unremarkable. As the area of depigmentation had undergone a minor change, a structural OCT scan was performed which demonstrated drusenoid changes but no cystic formation (Figure 3).
Figure 3. 2015: line scan shows hyper reflective drusen (Dec 2015)
Figure 4A. Normal avascular of the outer retinal layer. Figure 4B. Normal outer retinal layer highlighting the angio flow. Figure 4C. Normal choriocapillaris.
Three months later, the patient presented with symptoms of a central scotoma associated with deterioration in vision over a four-day period which then appeared to stabilise. The right acuity had dropped to <6/90 while the left eye was unchanged in acuity and appearance.
The change in the macular area is evident in Figure 2. The structural OCT of the right macula demonstrates a thick opaque lesion with marked disruption of the outer retinal layers including the photoreceptors and associated sub-retinal fluid (Figure 5).
Figure 5. Structural OCT of the macular area with a fibrovascular membrane (red arrows) and subretinal fluid (green arrows) with the approximate position of the outer retina between the green and yellow lines. The choriocapillaris is below the yellow line.
Figure 5A. The neovascular membrane (red arrows) in the outer retinal layer. Figure 5B. The neovascular membrane in the outer retina highlighted with the Angioflow. Figure 5C. The neovascular membrane in the choriocapillaris (red arrows).
OCT angiography was performed with the newly-acquired, upgraded equipment. The appearance of the avascular outer retinal area choriocapillaris and angioflow of a normal subject is shown in Figures 4A, 4B and 4C for comparison. The neovascular formation of this patient is clearly visible in Figures 5A, 5B and 5C.
The patient was referred to an ophthalmologist who performed a fluorescein angiogram but commented that the results were less revealing than that of the Angio OCT. The right eye was treated with an anti-VEGF injection. The OCT findings one month after injection are illustrated in Figures 6A, 6B and 6C, which show a significant decrease in sub-retinal fluid as well as the neovascular membrane in the outer retina and choriocapillaris.
Figure 6. Structural OCT illustrating the fibrovascular scar with a significant decrease in subretinal fluid following anti-VEGF injection.
Figures 6A. Significant decrease in the neovascular membrane in the outer retina after anti-VEGF. Figure 6B. Some normalisation of the outer retinal angio flow. Figure 6C. Partial normalisation of the vasculature of the choriocapillaris after anti-VEGF, some disorganisation still evident.
These results clearly demonstrate the potential benefit of OCT angiography in optometric and ophthalmological practice. If OCT angiography had been available at the previous examination, it may have been possible to detect the early stages of neovascularisation.
The impact of anti-VEGF treatment is also clearly demonstrated, which has been reported previously.4,9 However, as with any new modality which reveals previously unseen changes, it is important to establish relevance to prevent inaccurate diagnosis and unnecessary treatment. This emphasises the need for continuing education of clinicians in a time of unprecedented technological advancement if these benefits are to be delivered in practice.
1. Friedman DS, O’Colmain BJ, Munoz B et al. Prevalence of age-related macular degeneration in the United States. Arch Ophthalmol 2004, 122: 4: 564-572.
2. Ferris FL 3rd, Fine SL, Hyman L. Age-related macular degeneration and blindness due to neovascular maculopathy. Arch Ophthalmol 1984; 102: 11: 1640-1642.
3. Huang D et al. Imaging the eye from front to back with RTVue Fourier-domain optical coherence tomography. Thorofare, NJ: Slack, ©2010; 2010.
4. Lumbroso Bruno, Huang David, Jia Yali et al. Clinical guide to angio-OCT: non invasive, dyeless OCT angiography, 2015 ed. New Delhi: Jaypee, the Health Science Publishers; 2015.
5. Cocas Gabriel LM, Cocas Florence. Atlas OCT: Angiography in AMD: Comparison with Multimodal Imaging. In: Societe Francaise De Retine; 2015.
6. Lumbroso B, Huang D, Jia Y et al. Clinical OCT angiography atlas: New Delhi: Jaypee, the Health Science Publishers; 2015.
7. de Carlo TE, Romano A, Waheed NK, Duker JS. A review of optical coherence tomography angiography (OCTA). Int J Retina Vitreous 2015; 1: 5.
8. Marduel R. Angio OCT, dye less angiography, a new approach of age related macular degeneration (ARMD). Adv Ophthalmol Vis System 2015; 2: 2: 1-4.
9. Kuehlewein L, Sadda SR, Sarraf D. OCT angiography and sequential quantitative analysis of type 2 neovascularization after ranibizumab therapy. Eye (Lond) 2015; 29: 7: 932-935.
10. Lommatzsch A, Farecki ML, Book B et al. [OCT angiography for exudative age-related macular degeneration: Initial experiences]. Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft 2016; 113: 1: 23-29.
11. Jia Y, Bailey ST, Wilson DJ et al. Quantitative optical coherence tomography angiography of choroidal neovascularization in age-related macular degeneration. Ophthalmology 2014; 121: 7: 1435-1444.