Long-term effect of intravitreal aflibercept treatment on choroidal vascularity index in neovascular age-related macular degeneration

Perifoveal retinal thickness changes after intravitreal aflibercept injection for choroidal neovascularization in age-related macular degeneration

OBJECTIVE

There has been some concern that anti-vascular growth factor treatment accelerates the development of macular atrophy in eyes with neovascular age-related macular degeneration. During the treatment with aflibercept, the thickness of choroid may decrease. This may lead to photoreceptor death. The rod cells are more susceptible to atrophic changes than cones during the disease. We aimed to find any thickness changes in the perifoveal outer nuclear layer, where the highest density of rods is found, during the aflibercept intravitreal injection therapy.

MATERIALS AND METHODS

Retrospectively, forty-two patients who were treated for age-related macular degeneration with choroidal neovascularization were included in the study. After the first three loading doses, intravitreal injections were repeated every two months. Outer nuclear layer thicknesses were measured 2000 µm away from the center of the fovea with OCT, at a total of 20 points, located at 180 and 90°. The mean of these measurements was obtained before the treatment and 1 year after the therapy. Results were compared by using the Wilcoxon Rank Test.

RESULTS

The mean visual acuity was 1,11±0,287 logMAR at the beginning and increased to 0,53±0,32 LogMAR after. Perifoveal thickness was significantly reduced when compared with the thickness before the treatment (p = 0.039, p < 0.05). This result was also significantly lower than the control group thicknesses (p = 0.035, p < 0.05).

CONCLUSION

Anti-VEGFs can cause loss of phagocytic functions of RPE. The mechanism of the observed thinning of the ONL may be described as follows: VEGF emitted by the RPE normally helps to maintain the choriocapillaris. Thus, injecting an anti-VEGF intravitreally causes RPE atrophy, which leads to a decrease in the choroidal vascular index. This in turn causes first the rods, and later the cones, that are part of the outer nuclear layer, to start to die and disappear, hence the thinning of this layer. As aflibercept consists of parts of the extracellular domain of both the VEGFR1 and VEGFR2 receptors, that are held together by a human IgG1 backbone, this makes the binding of aflibercept to VEGF-A and VEGF-B stronger as compared to the binding of the previously used ranibizumab or bevacizumab (by nearly a factor 100 in the case of the most abundant isoform VEGF-A 165). Besides, aflibercept also binds very well to placental growth factor (PIGF), which is also associated with several ocular diseases.

Choroidal remodeling following different anti-VEGF therapies in neovascular AMD

The purpose of this study was to investigate choroidal morphology remodeling in AMD-associated type 1 macular neovascularization using two different anti-VEGF drugs. We registered 73 treatment-naïve eyes with a diagnosis of exudative AMD and type 1 MNV. Patients received 3 monthly intravitreal aflibercept (n = 36, aflibercept group [AG]) or brolucizumab (n = 37, brolucizumab group [BG]). Baseline best-corrected visual acuity (BCVA) and anatomical (structural optical coherence tomography) parameters were collected at "T1 control", before the loading phase (LP) of intravitreal injection, and at "T2 control", 1 month after the last injection. The main outcomes measured were choroidal vascularity index (CVI), sub-foveal choroidal thickness (SFCT), and central macular thickness (CMT). Our results displayed significant SFCT reduction in both groups between T1 and T2 (p < 0.05), We did not find choroidal vascularity modifications (p > 0.05) after the loading aflibercept injections. Moreover, only the BG displayed a significant choroidal remodeling (stromal choroidal area [SCA], total choroidal area [TCA] and CVI) at T2 (p < 0.05). In particular, a relevant stromal and total choroidal volume reduction was noted, accompanied by an increase in CVI. To conclude, the latter modifications of the choroidal morphology were found significant between two groups (p < 0.05). Our analysis showed a significant impact of brolucizumab on choroidal morphology in eyes affected by type 1 nAMD. This effect was found relevant when compared with aflibercept.