8.3.2  Idiopathic Polypoidal Choroidal

Vasculopathy

The term IPCV stands for a separate clinical entity that 8  differs clinically and demographically from AMD [47].

ICG and OCT studies revealed that polypoidal vascular lesions of the choroid are associated with serous and hemorrhagic RPE detachments [48, 49]

The variable presentation of IPCV gives rise to equally variable NIR images. RPE detachments and serous retinal elevations have a similar aspect as vascularized RPE detachments in AMD (Sect. 8.3.1.3). However, the localization and the source of the underlying subretinal structures separate IPCV from a regular AMD-associated RPE detachment on NIR imaging (Fig. 8.10). The polypoidal structures can be identified by their increased signal on NIR that collocates with their position on ICGA. The bright reflex represents the typically elongated, large vessel­ -like structures, as opposed to the adjacent smallsized signals of RPE alterations and the large, round reflexes of RPE detachments.

8.3.3  Fibrovascular Scar

Following treatment or in the later stages of a wet AMD, a degenerative process will lead to vessel occlusion and the development of scar tissue within the neovascular lesion. This scar consists of dense fibrous tissue, possibly surrounded by fibrinous exudations [50]. Higher levels of collagen fibers will lead to increased scattering and reflectance within the tissue, consequently enlarging the NIR signal [51]. Therefore, fibrovascular scars can be identified by their exceedingly bright appearance on NIR imaging (Fig. 8.11). Depending on a residual elevation of the overlying retina, a dark halo may be observed in the vicinity of the scar. In addition, there may be co-existing active parts of a CNV with the typical NIR manifestations as described in Sect. 8.3.1.1 through 8.3.4.

Summary for the Clinician

■The location of the neovascular membrane in relation to the RPE has its effects on the resultant NIR image.

■A dark, often poorly defined halo around the lesion is a frequent finding in the NIR of exudative macular degeneration and correlates with active CNV leakage on fluorescein angiography.

■On the NIR image, a bright corona surrounding a dark core is the characteristic sign of a welldefined, classic CNV.

■Occult CNV lesions show poorly demarked areas of scattered NIR increase with an underlying dark halo.

■In RPE detachments, a thin, lighter corona encircles an area of normal to low reflectivity, including scattered NIR increase at the area of the CNV.

■The darkened halo in RAP often exceeds the leakage zone on fluorescein angiography, possibly as a result of pre-edematous Müller cell disease. The RAP lesion itself appears as an irregular, increased NIR signal.

■Abnormal vessels in IPCV are mirrored by relatively high-reflective, elongated structures on NIR imaging.

■In the end stage of CNV membranes, the densepacked collagen fibers in fibrovascular scars produce­ a very strong NIR signal.

8.3.4  Choroidal Neovascularization

Not Associated with AMD

A variety of other disorders like high myopia, retinal dystrophies, uveitis, or idiopathic genesis may account for the development of CNV [52–54]. The majority of these neovascularization appear to be of the well-defined classic type. Coexisting retinal changes associated with underlying disorder, however, may confuse the interpretation of the NIR image. For instance, non-neovascular fundus lesions like inflammatory spots may also have increased fluid content and cause a locally elevated retina, giving rise to NIR abnormalities not unlike CNVs.

8.4  Evaluating Therapeutic Effects

with Near-Infrared Reflectance Imaging

The evolving new therapeutic strategies in CNV treatment require repeated imaging of the fundus to monitor the treatment effects and to aid in the appropriate timing for re-treatment [55]. Besides fluorescein angiography as the gold-standard for the assessment of CNV activity, OCT has become a widely accepted noninvasive tool in the evaluation of AMD therapy [56]. However, OCT data are not directly comparable with fluorescein angiography results due to their essential differences. Besides the static character of the anatomical OCT image, the huge memory capacity needed for modern three-dimensional OCT may be a drawback. Fluorescein angiography evaluates the functional aspects of the CNV by dynamic imaging