Choroidal Neovascularization: OCT Angiography Findings
Choroidal neovascularization (CNV) is part of the spectrum of exudative age-related macular degeneration (AMD) that consists of an abnormal growth of vessels from the choroidal vasculature to the neurosensory retina through the Bruch's membrane. Leakage of retinal edema and hemorrhage from CNV in exudative AMD threatens visual acuity.
Etiology of CNV is multifactorial. Alterations in Bruch's membrane, migration of macrophages and production of vascular endothelium growth factor (VEGF), play an important role in 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 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 large, confluent soft drusen. . Oxidative stress may play an important role in AMD. Several modifiable risk factors have been identified, including quitting 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. Hypoxia leads to VEGF being released by RPE that initiates a cascade of angiogenic responses at the level of the choroidal endothelium. Bruch´s membrane damage is required to allow the passage of abnormal neovascular vessels from the choroidal vasculature through the breaks in Bruch’s membrane 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, passes through the RPE and is located above the RPE in the subretinal space. This is related to angiographic classification: type 1 corresponds to hidden CNV and type 2 corresponds to classic CNV. Type 3 is defined as Retinal Angiomatous Proliferation (RAP), which corresponds to neovascularization that develops within the neurosensory retina.
In the presence of CNV, the patient experiences an acute decrease in visual acuity, relative scotoma and metamorphopsia. The retinal examination shows a grayish macular lesion associated with subretinal fluid, cystoid macular edema, exudation and hemorrhages.
OCT ANGIOGRAPHY OCT ANGIOGRAPHY: En face OCT angiography (OCTA) is a new technology that has a great ability to show detailed retinal structures and chorioretinal microcirculation without contrast medium or without invasive means. It uses an optimized long wavelength (1,050nm), which can penetarte 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, originating in the choroid. The type 2 CNV is visualized as a neovascular network that grows from the choroid vasculature, traverses the RPE-Bruch's membrane complex into the subretinal space. Type 3 CNV is clinically seen as tiny intra- and subretinal hemorrhages that correlate on OCT-A to an intraretinal anastomosis originating in the deep capillary plexus of the retina.
Taking into account the numerous recent studies on the treatment of CNV in AMD, it has been shown that antiangiogenic therapy shows the best result both histologically with the regression of the neovascular lesion and functionally with 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