Choroidal Neovascularization: OCT Angiography Findings
Choroidal neovascularization (CNV) is part of the spectrum of age-related macular degeneration (AMD) consisting of the abnormal growth of vessels from the choroidal vasculature to the neurosensory retina through the Bruch's membrane. Exudative AMD is the main complication that threatens visual acuity.
CNV is a multifactorial lesion, produced due to numerous stimuli. Alterations in Bruch's membrane, involvement of macrophages and vascular endothelium growth factor (VEGF), take the main role for the development of this disease.
The incidence and progression of AMD are related to age and genetic factors. With aging, the lysosomal activity for the degradation of external segments of photoreceptors decreases. This leads to a subsequent accumulation of lipofuscin, which affects the normal function of the RPE. Another important risk factor for the development of CNV is the presence of soft drusen as opposed to hard ones.
Several modifiable risk factors have been identified, including smoking, dietary intake of omega-3 fatty acids and vegetables and fruit with antioxidants including lutein and zeaxanthin, as well as, exercise, and maintaining a healthy weight.
Alterations in the normal transport of metabolites, ions and water through Bruch's membrane in AMD, alter the nutrition and stability of retinal pigment epithelium (RPE) from choriocapillaris and the transport of waste out from the neurosensory retina. VEGF is then released by RPE as a stress signal and hypoxia that initiates a cascade of angiogenic responses at the choroidal endothelium level. Bruch´s membrane damage is required to allow neovascular passage through it from the choroidal vasculature to the retina. This impairment is part of the pathological course of AMD
Histologically, neovascular membranes are classified into: Type 1, when the neovascular membrane is located below the RPE Type 2, as it passes through the RPE, compromising the neurosensory retina
This has been related to angiographic classification: type 1 corresponds to hidden CNV and type 2 corresponds to classic CNV.
Type 3 has been defined as RAP (Retinal Angiomatous Proliferation), which corresponds to neovascularization developed within the neurosensory retina.
In the presence of CNV, the patient refers a sudden decrease in visual acuity and metamorphopsia. The ophthalmologic examination shows a grayish macular lesion associated with subretinal fluid, exudation and hemorrhages.
OCT ANGIOGRAPHY En face OCT angiography (OCTA) is a new technology that has a great ability to detail retinal structures and chorioretinal microcirculation without contrast medium or without invasive means. It uses an optimized long wavelength (1,050nm), which achieves a better penetration of deeper layers of the eye and can traverse opacities of media such as cataracts, hemorrhages, vitreous opacities, pigment, among others. It can also configure three-dimensional analysis of the chorioretinal and vascular lesions.
Type 1 CNV is observed by OCT-A as a neovascular coralliform complex with afferent vessel, originated in the choroid. The type 2 CNV is visualized as a neovascular network that is born from the choroid traverses the EPR-MB complex to compromise the external retina. Type 3 is identified as an intra- and subretinal bleeding correlated in OCT-A with an intraretinal anastomosis originating in the deep capillary plexus of the retina.
Taking into account the numerous and recent studies on the treatment of CNV in AMD, it has been shown that antiangiogenic therapy is the one that has shown the best results both histologically with the regression of the neovascular lesion and functionally with the improvement of the visual acuity. Although the treatment is the same for all types of CNV, it is important to differentiate them, since they do not all respond identically and some of them have a higher rate of recurrence.
- Klein R, Klein BE, Jensen SC, et al. The five-year incidence and progression of age-related maculopathy: the Beaver Dam Eye Study [see comments]. Ophthalmology 1997;104:7–21.
- Wilcox DK. Vectorial accumulation of cathepsin D in retinal pigmented epithelium: effects of age. Invest Ophthalmol Vis Sci 1988;29:1205–12.
- Tombran-Tink J, Shivaram SM, Chader GJ, et al. Expression, secretion, and age-related downregulation of pigment epithelium-derived factor, a serpin with neurotrophic activity. J Neurosci 1995;15:4992–5003.
- Kennedy CJ, Rakoczy PE, Constable IJ. Lipofuscin of the retinal pigment epithelium: a review. Eye 1995;9:763–71.
- Rakoczy PE, Zhang D, Robertson T, et al. Progressive age-related changes similar to age-related macular degeneration in a transgenic mouse model. Am J Pathol 2002;161:1515–24.
- Hageman GS, Mullins RF. Molecular composition of drusen as related to substructural phenotype. Mol Vis 1999;5:28.
- Mullins RF, Russell SR, Anderson DH, et al. Drusen associated with aging and age-related macular degeneration contain proteins common to extracel- lular deposits associated with atherosclerosis, elastosis, amyloidosis, and dense deposit disease. FASEB J 2000;14:835–46.
- Sarks JP, Sarks SH, Killingsworth MC. Evolution of soft drusen in age-related macular degeneration. Eye 1994;8:269–83.
- Abdelsalam A, Del Priore L, Zarbin MA. Drusen in age-related macular degeneration: pathogenesis, natural course, and laser photocoagulation- induced regression. Surv Ophthalmol 1999;44:1–29.
- Carnevali A, Cicinelli MV, Capuano V, Corvi F, Mazzaferro A, Querques L, et al. Optical Coherence Tomography Angiography: A Useful Tool for Diagnosis of Treatment-Naïve Quiescent Choroidal Neovascularization. Am J Ophthalmol [Internet]. 2016;169:189–98. Available from: http://dx.doi.org/10.1016/j.ajo.2016.06.042
- Huang D, Jia Y, Rispoli M, Tan O, Lumbroso B. Optical Coherence Tomography Angiography of Time Course of Choroidal Neovascularization in Response To Anti-Angiogenic Treatment. Retina [Internet]. 2015;35(11):2260–4. Available from: http://www.ncbi.nlm.nih.gov/pubmed/26469535
- Jia Y, Bailey ST, Wilson DJ, Tan O, Klein ML, Flaxel CJ, et al. Quantitative optical coherence tomography angiography of choroidal neovascularization in age-related macular degeneration. Ophthalmology [Internet]. 2014;121(7):1435–44. Available from: http://dx.doi.org/10.1016/j.ophtha.2014.01.034
- Lumbroso B, Rispoli M, Savastano MC. Longitudinal Optical Coherence Tomography–Angiography Study of Type 2 Naive Choroidal Neovascularization Early Response After Treatment. Retina [Internet]. 2015;35(11):2242–51. Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&CSC=Y&NEWS=N&PAGE=fulltext&D=emed13&AN=2015490570%5Cnhttp://sfx.ucl.ac.uk/sfx_local?sid=OVID:embase&id=pmid:&id=doi:&issn=0275-004X&isbn=&volume=35&issue=11&spage=2242&pages=2242-2251&date=2015&title=Retina&atitle=Lon