Author: Cecilia Mularoni (Italy)
Co-authors: Alessandro Arrigo, Emanuela Aragona, Francesco Bandello, Maurizio Battaglia Parodi
Quantitative optical coherence tomography angiography (OCTA) allowed to perform several steps forward in the comprehension of the complex pathogenesis of macular neovascularization (MNV) secondary to age-related macular degeneration. This study investigated the quantitative OCTA parameters associated with size modifications of neovascular network over 1 year of follow-up and treatment. The main aim was to identify the factors involved in the MNV size changes over follow-up, especially pointing out the role of MNV vessel tortuosity (VT), MNV reflectivity and MNV subtypes. Moreover, we evaluated the potential predictive role of these factors regarding the direction of the expansion or reduction of the neovascular lesion over the follow-up.
The study was designed as a prospective, cohort study, with a 1-year follow-up. All the patients were recruited at the Ophthalmology Unit of IRCCS San Raffaele Scientific Institute, Milan, Italy. Signed, informed consent was obtained from all patients. The study was approved by the Ethical Committee of IRCCS San Raffaele Scientific Institute in Milan and was conducted in accordance with the Declaration of Helsinki.
The study included patients with type 1, mixed or type 2 MNV diagnosed by structural OCT and by fluorescein angiography (FA) examinations. We excluded all the other MNV lesions because they are not easily detectable on OCTA. All the patients underwent Ranibizumab 0.5 mg intravitreal treatment, including a loading dose with 3 monthly injections, followed by further anti-VEGF administrations according to a treat and extend regimen. In the study, we measured for each eye the vessel tortuosity (VT) considering it as an indirect sign of MNV blood perfusion, higher values corresponding to a higher blood flow. We applied a MNV VT cutoff of 8.40 to obtain Group 1 (MNV VT<8.40) and Group 2 (MNV VT>8.40) at baseline. In addition, we calculated the reflectivity value of the MNV area and we divided it in eight different sectors. In the sectors displaying low reflectivity at baseline, we observed if MNV size changes occurred at the end of the follow-up, considering only cases with at least 20% of size difference during the study. All the measurements were performed at baseline, after the loading dose of 3 anti-VEGF injections and at the end of the 1-year follow-up.
We recruited 28 eyes (28 patients). Mean BCVA was 0.36±0.21 LogMAR, improved to 0.28±0.22 Log-MAR (p<0.01) with a mean number of 8±3 injections. 15 eyes showed MNV type 1 (54%), 9 mixed type (32%), 4 type 2 (14%). Eyes belonging to MNV VT>8.40 group (50% of our cases) showed worse outcome in terms of BCVA, OCTA parameters and outer retinal atrophy (46%vs20%; p<0.01) Furthermore, a mean MNV reflectivity value of 101 was associated with high probability of changes in MNV size (larger or smaller). MNV growth was directly related to MNV VT values. In particular, MNV VT>8.40 was associated with higher increases in MNV size (p<0.01). Moreover, MNV growth was influenced by the type, with type 2 and mixed type lesions being related with greater expansions in MNV size (p<0.01). Remarkably, the association of MNV type + MNV VT>8.40 was associated with higher MNV enlargement rate (p<0.01). MNV sectors showing low reflectivity values resulted prone to greater neovascular growth (p<0.01). MNV type 2 (or mixed type) combined with MNV VT >8.40 and low MNV reflectivity showed cumulative effect in determining MNV expansion (p<0.01). Conversely, MNV lesions with low VT values might experience size reductions (34 % of cases).
The study highlighted quantitative OCTA parameters associated with changes of MNV lesions. These metrics lead to the identification of highly perfused MNV lesions, to the assessment of MNV size modifications and of the direction of the expansion. In particular, higher MNV VT values were correlated with more aggressive lesions and with greater MNV growing during the follow-up. Furthermore, we found a cumulative effect of type 2 or mixed MNV associated with MNV VT>8.40 and low MNV reflectivity values on MNV size increase. The lower MNV reflectivity might be correlated with immature and unstable neovascular structures which can undergo more size changes with respect to neovascular network mainly characterized by higher MNV reflectivity values. In our investigation, the number of intravitreal injections was not significantly associated with modifications of the quantitative OCTA parameters. In conclusion, the proposed OCTA-based approach provided a way to quantitatively characterize the dinamic changes occuring in AMD-related MNV.
I have no disclosures to declare.