Type 3 macular neovascularisation (MNV) due to age-related macular degeneration
Reviewed by Sofia Rokerya

This paper systematically reviews and summarises the current knowledge on type 3 neovascularisation due to age-related macular degeneration which is defined as neovascularisation originating from the retinal deep capillary plexus that grows towards the outer retina often penetrating the level of retinal pigment epithelium (RPE). Its frequency appears to be higher than was previously thought and because there is a high incidence of bilateral involvement, it is making the follow-up and regular monitoring of the fellow eye mandatory. MNV3 lesions are located between 500 microns to 1500 microns from the central fovea and therefore not found in the foveal avascular zone (FAZ). Ocular coherence tomography (OCT) angiography imaging has not only made an important contribution to the pathophysiological characterisation of MNV3 but has also provided an additional biomarker for practical guidance in the treatment and monitoring of MNV3. Hyperreflective foci (HRF) in the outer retina possibly represent a precursor lesion. MNV3 is characterised by a strong association with reticular pseudo drusen, a high rate of bilaterality, close associations with advanced age, arterial hypertension, decreased choroidal thickness, and decreased choriocapillaris flow signals. Data from latest anti-vascular endothelial growth factor studies in MNV3 suggest that the OCT biomarkers in intraretinal and subretinal fluids should be interpreted differently than in the other types. MNV3 can be divided into the following stages: Stage one is defined as intraretinal HRF associated with cystoid macular oedema without outer retinal disruption. In stage two, there is an intraretinal HRF with cystoid macular oedema and outer retinal disruption with or without RPE disruption. Stage three represents a progressive downward growth of the MNV3 lesion, proliferating through the RPE and creating a vascularised serous pigment epithelial detachment (PED). The natural history of MNV3 is characterised by exudative maculopathy, leading to severe and rapid visual loss in a large proportion of patients. Before the introduction of intravitreal anti-VEGF for the treatment of MNV3, various approaches of laser photocoagulation were used – photodynamic therapy, transpupillary thermotherapy, and intravitreal triamcinolone acetonide were other modalities of treatment each of which resulted only in modest improvement and / or short-term improvement in visual acuity. Better visual outcomes reflected in morphological changes demonstrated on OCT were achieved with intravitreal anti-VEGF injections. When treated early MNV3 lesions are found to be very responsive to anti-VEGF therapy. It has been postulated that because these lesions are intraretinal, they tend to become symptomatic earlier than other types, resulting in less mature vessels, hence earlier treatment and better response. The paper opens the avenues for further research on optimal type-specific future treatment strategies.

Current perspectives on type 3 macular neovascularization due to age-related macular degeneration.
Clemens CR, Eter N, Alte F.
OPHTHALMOLOGICA
2024;247:73–84.