Author: Andrea Saladino (Italy)
Co-authors: Alessandro Arrigo, Emanuela Aragona, Alessandro Bordato, Alessia Amato, Francesco Maria Bandello, Maurizio Battaglia Parodi
Purpose
Optical coherence tomography (OCT) angiography (OCTA) has changed the approach to a AMD patient and its staging thanks to the capacity to detect MNV without intravenous dye. The vessels morphology visible with OCTA is not a fully structural reconstruction of the neovascularization and usually appears smaller than the ones seen by fluorescein angiography (FA) and indocyanine green angiography (ICGA). In this study, we aimed to discriminate high reflectivity and low reflectivity macular neovascularization (MNV) lesions secondary to age-related macular degeneration (AMD)and to assess the influence of blood flow features on the amount of MNV detected by optical coherence tomography angiography (OCTA).
Setting/Venue
The study is designed as a cross-sectional, observational case series. It was totally placed in at the Department of Ophthalmology of IRCCS San Raffaele Hospital, Milan, Italy. Each patient signed an informed consent approuved by the ethical committee of IRCCS Scientific Institute San Raffaele Hospital.
Methods
Pseudophakic patients affected by type-1 or type-2 naïve MNV were recruited from January 2018 to January 2019 . Polypoidal choroidal vasculopathy (PCV) and retinal angiomatous proliferation (RAP),whose pattern are hardly detectable by OCTA, such as media opacities, ophthalmologic surgery within the last six months and any ophthalmologic or systemic condition potentially affecting the analyses where considered as exclusion criteria. The analysis starts from the most superficial portion of the MNV lesion obtained from one segmentation, modifying the boundaries in order to underline the deepest portion of the MNV. Using the mean reflectivity value as a threshold for each MNV we divided them into low and high flow vessels respectively for the once with poor and the elevated reflectivity. Then we compared OCTA highlights (degree, size and quantitative reflectivity) to dye angiography features.
Results
Fifty eyes from 50 patients were included into the study. We classify MNV as follows: 35 (70%) type 1 and 15 (30%) type 2. The mean OCTA reflectivity values were 100±15 for type 1 MNV and 120±10 for type 2 MNV (p˂0.01). Taking these values as thresholds, we found that 85%±5% of the entire type 2 MNV was distinguished by highly detected flow, whereas the proportion was just 56%±12% in type 1 MNV (p˂0.01) (Fig. 4). In both cases, the poorly detected flow signal was distributed mainly in the peripheral MNV region. We found a good agreement between early ICGA size and OCTA size for type 1 MNV (2.10±1.91mm2 vs 2.09±1.87mm2; p˃0.05), whereas MNV lesions turned out to be remarkably bigger on late ICGA phase (3.41±2.87mm2; p˂0.01). Interestingly, OCTA well-matched with FA in terms of MNV size for type 2 lesions (2.36±2.15mm2 vs 2.37±2.25mm2). MNV reflectivity was higher in type 2 MNV and it was strongly associated with the OCTA ability to reconstruct the neovascular network.
Conlusions
MNV size appears larger on FA/ICGA than on OCTA, corroborating the findings of previous investigations. In particular, the type 1 MNV plaque can be visualized in its entirety in the late stages of the ICGA examination, proving to be significantly larger than the corresponding OCTA reconstruction. On the other hand, type 2 MNV showed unvaried size in both early and late stages of FA/ICGA examination and offered an excellent match with the corresponding OCTA reconstruction. In our cohort of patients, type 2 MNV lesions turned out to be significantly more detected on OCTA than type 1 MNV, as assessed by the mean reflectivity intensity calculated from OCTA reconstructions. Furthermore we found the highly detected flow signal to be more evenly distributed in type 2 MNV than in type 1 MNV. The type 1 MNV filling signal, which is slower and less intense in perfusion in periphery, smaller new vessels proved to be poorly detected by OCTA or not detected at all, probably because of the limits of current OCTA devices which cannot detect a blood flow signal under a speed cut-off.
Financial Disclosure
none
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