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

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. 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 microns away from the center of the fovea with OCT, at a total of 20 points, located at 180 and 90 degrees. 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. 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). 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 iso form VEGF-A 165). Besides, aflibercept also binds very well to placental growth factor (PIGF), which is also associated with several ocular diseases.