MyVisionTest News Archive
Oct 22, 2009
3D-OCT in neovascular AMD
3D-OCT provided realistic anatomic maps of the retina in patients with age-related macular degneration (AMD), according to a new study.
Numerous diagnostic tools such as optical coherence tomography (OCT) three-dimensional (3D)-OCT retinal thickness analysis (RTA), and topographic angiography (TAG) are being evaluated clinically, in addition to the conventional techniques such as fluorescein angiography (FA) and biomicroscopy. These methods provide improved capabilities for the imaging of the intraretinal morphology. Most important, they offer realistic 3D imaging of retinal and subretinal levels in various macular diseases.
Methods and Results
In this comparative clinical study, 37 consecutive patients with classic, minimally classic, or occult CNV; 13 patients with early AMD; and 10 age-matched healthy individuals were included. HD-OCT imaging (Topcon, Tokyo, Japan) and FA (scanning retinal ophthalmoscope; HRA2; Heidelberg Engineering, Dossenheim, Germany) were performed after a complete standardized ophthalmic examination. Only one eye of each patient was included in the study. A point-to-point correlation between HD-OCT and FA images was performed. Early and late FA images at defined locations were correlated with OCT measurements, including 3D maps, 2D single scans, a thickness linear graph, and the 3D retinal pigment epithelium (RPE) segmentation.
With HD-OCT imaging used to delineate the lesion morphology, early AMD was detected as having a normal foveal contour and minimal alteration in the macular area; classic CNV as a well-defined lesion with steep margins and a craterlike configuration, occult CNV as an ill-defined, flat lesion with a convex surface; and minimally classic CNV as having classic and occult components. FA-OCT overlay images provided a significant correlation between FA patterns and OCT features such as retinal thickness (RT).
Discussion and Conclusions
In exudative macular disease, hemorrhage, subretinal fluid, and cystoid edema are common findings, reflecting the vascular nature of the underlying disease. Specific diagnostic tools are available in clinical practice to evaluate CNV-related disease. Standard methods remain FA, indocyanine green angiography (ICGA), and, increasingly, OCT. FA highlights the features of classic and occult lesion components and extravasation originating from the leaky neovascular channels in a qualitative way. However, quantitative data on leakage activity may only be estimated (e.g., as leakage area in late-phase FA). The differentiation between staining and leakage remains a substantial problem in FA-based analysis.
ICGA complements FA in the diagnosis of occult lesions, where masking phenomena may prevent the visualization of the neovascular net and is less dependent on leakage as ICGA bound to albumin is kept intravascularly. In contrast, OCT offers the complementary ability of imaging the retinal structures and the level of retinal involvement by the CNV, but is compromised in terms of identifying the subretinal neovascular correlate in general and particularly with respect to the specific lesion’s composition. This deficiency is mainly based on the restrictions of conventional OCT.
Many of the aspects that render conventional OCT inferior to angiography are overcome by the novel SD-OCT technology. SD-OCT offers high resolution and short acquisition times, allowing scanning of the macular area in a dense raster pattern, realistically measuring RT and reconstructing a 3D relief of the retinal condition. The novel SD-OCT should therefore compare more favorably with angiography.
In this study, we evaluated the ability of 3D SD-OCT imaging to distinguish among the characteristic types of AMD. The morphologic OCT findings correlated with those of conventional FA.
Characteristic morphologic 2D and 3D features were consistently identified by 3D-OCT: classic CNV imaged as a retinal lesion with two steep and high elevations separated by a depression in the center, which obviously represents the impact of subretinal CNV infiltration on the integrity and thickness of the overlying retina. Occult CNV was identified as a slightly elevated prominence with convex surface. With these features SD-OCT contributes significantly to the differential diagnosis of lesion composition.
In addition to the detailed identification of the primary underlying neovascular correlate, the secondary leakage-induced changes in the retinal morphology can be qualified and quantified by analysis of the 2D scans and the retinal map as well as the RT measurement. Both aspects, origin and consequence, of active CNV are delineated by 3D-OCT analysis based on an RT map and an RPE segmentation map.
FA evaluation is less informative, as occult components may not be clearly detected and delineated, and the intensity and extent of the active leakage cannot be measured precisely. Moreover, OCT easily differentiates between leakage and staining as the hyperfluorescence induced by the latter represents visualization of fibrotic tissue and not edema, which appears as a thickening of the hyperreflective RPE band on OCT.
In conclusion, 3D-OCT offers the ability to identify AMD at all its anatomic levels, in a noninvasive and practical approach. Discrimination between the predominant CNV lesion types was achieved, and their precise shape was identified, together with information about the lesion’s localization and leakage activity.
WHAT IT MEANS TO YOU: One explanation that has been proposed for the vision loss associated with as-needed anti-VEGF therapy is that conventional OCT may fail to detect subtle leakage. As imaging technology improves there is less chance that mild leakage will be missed, and less need for invasive and potentially hazardous fluorescein angiography.
Read more...
Invest Ophthalmol Vis Sci. 2009 Oct;50(10):4926-33
3D-OCT provided realistic anatomic maps of the retina in patients with age-related macular degneration (AMD), according to a new study.Numerous diagnostic tools such as optical coherence tomography (OCT) three-dimensional (3D)-OCT retinal thickness analysis (RTA), and topographic angiography (TAG) are being evaluated clinically, in addition to the conventional techniques such as fluorescein angiography (FA) and biomicroscopy. These methods provide improved capabilities for the imaging of the intraretinal morphology. Most important, they offer realistic 3D imaging of retinal and subretinal levels in various macular diseases.
In this comparative clinical study, 37 consecutive patients with classic, minimally classic, or occult CNV; 13 patients with early AMD; and 10 age-matched healthy individuals were included. HD-OCT imaging (Topcon, Tokyo, Japan) and FA (scanning retinal ophthalmoscope; HRA2; Heidelberg Engineering, Dossenheim, Germany) were performed after a complete standardized ophthalmic examination. Only one eye of each patient was included in the study. A point-to-point correlation between HD-OCT and FA images was performed. Early and late FA images at defined locations were correlated with OCT measurements, including 3D maps, 2D single scans, a thickness linear graph, and the 3D retinal pigment epithelium (RPE) segmentation.
With HD-OCT imaging used to delineate the lesion morphology, early AMD was detected as having a normal foveal contour and minimal alteration in the macular area; classic CNV as a well-defined lesion with steep margins and a craterlike configuration, occult CNV as an ill-defined, flat lesion with a convex surface; and minimally classic CNV as having classic and occult components. FA-OCT overlay images provided a significant correlation between FA patterns and OCT features such as retinal thickness (RT).
Discussion and Conclusions
In exudative macular disease, hemorrhage, subretinal fluid, and cystoid edema are common findings, reflecting the vascular nature of the underlying disease. Specific diagnostic tools are available in clinical practice to evaluate CNV-related disease. Standard methods remain FA, indocyanine green angiography (ICGA), and, increasingly, OCT. FA highlights the features of classic and occult lesion components and extravasation originating from the leaky neovascular channels in a qualitative way. However, quantitative data on leakage activity may only be estimated (e.g., as leakage area in late-phase FA). The differentiation between staining and leakage remains a substantial problem in FA-based analysis.
ICGA complements FA in the diagnosis of occult lesions, where masking phenomena may prevent the visualization of the neovascular net and is less dependent on leakage as ICGA bound to albumin is kept intravascularly. In contrast, OCT offers the complementary ability of imaging the retinal structures and the level of retinal involvement by the CNV, but is compromised in terms of identifying the subretinal neovascular correlate in general and particularly with respect to the specific lesion’s composition. This deficiency is mainly based on the restrictions of conventional OCT. Many of the aspects that render conventional OCT inferior to angiography are overcome by the novel SD-OCT technology. SD-OCT offers high resolution and short acquisition times, allowing scanning of the macular area in a dense raster pattern, realistically measuring RT and reconstructing a 3D relief of the retinal condition. The novel SD-OCT should therefore compare more favorably with angiography.
In this study, we evaluated the ability of 3D SD-OCT imaging to distinguish among the characteristic types of AMD. The morphologic OCT findings correlated with those of conventional FA.
Characteristic morphologic 2D and 3D features were consistently identified by 3D-OCT: classic CNV imaged as a retinal lesion with two steep and high elevations separated by a depression in the center, which obviously represents the impact of subretinal CNV infiltration on the integrity and thickness of the overlying retina. Occult CNV was identified as a slightly elevated prominence with convex surface. With these features SD-OCT contributes significantly to the differential diagnosis of lesion composition.
In addition to the detailed identification of the primary underlying neovascular correlate, the secondary leakage-induced changes in the retinal morphology can be qualified and quantified by analysis of the 2D scans and the retinal map as well as the RT measurement. Both aspects, origin and consequence, of active CNV are delineated by 3D-OCT analysis based on an RT map and an RPE segmentation map.
FA evaluation is less informative, as occult components may not be clearly detected and delineated, and the intensity and extent of the active leakage cannot be measured precisely. Moreover, OCT easily differentiates between leakage and staining as the hyperfluorescence induced by the latter represents visualization of fibrotic tissue and not edema, which appears as a thickening of the hyperreflective RPE band on OCT.
In conclusion, 3D-OCT offers the ability to identify AMD at all its anatomic levels, in a noninvasive and practical approach. Discrimination between the predominant CNV lesion types was achieved, and their precise shape was identified, together with information about the lesion’s localization and leakage activity.
WHAT IT MEANS TO YOU: One explanation that has been proposed for the vision loss associated with as-needed anti-VEGF therapy is that conventional OCT may fail to detect subtle leakage. As imaging technology improves there is less chance that mild leakage will be missed, and less need for invasive and potentially hazardous fluorescein angiography.
Read more...
Invest Ophthalmol Vis Sci. 2009 Oct;50(10):4926-33
