Optical coherence tomography angiography findings of fellow eye of proliferative macular telangiectasia type 2: Long term study.

To report the characteristics of non-proliferative fellow eyes in patients with unilateral proliferative macular telangiectasia type 2 (MacTel). This was a multicenter, retrospective study and included fellow eyes of eyes with subretinal neovascular membrane (SRNVM). Multimodal imaging including fundus photography, optical coherence tomography (OCT), and OCT angiography (OCTA) was performed. OCT and OCTA measurements included central macular thickness (CMT), subfoveal choroidal thickness (SFCT), foveal avascular zone (FAZ) area and qualitative parameters such as distortion or enlargement of FAZ, increased inter-vascular spacing, dilated, tortuous vessel at margin of FAZ, crowding of vessel, and loss of choriocapillaris (CC). Thirteen fellow eyes of 13 patients with mean age of 63.6 ± 12.0 years were included. Fellow eyes had various stages of the diseases - stage 2 (four eyes), 3 (six eyes), and 4 (three eyes). OCTA showed increased intervascular spacing (8; 61.5%), dilated (11; 84.6%), and elongated vessels (8; 61.5%) at the margin of the FAZ, crowding of vessels (6; 46.2%), capillary non-perfusion areas outside the FAZ (4; 30.8%), and areas of CC loss (4; 30.8%). Mean follow-up was 9.1 ± 12.9 months. Out of six eyes with follow-up of ⩾12 months, two developed SRNVM at 18 and 33 months with OCTA showing crowding and entanglement of dilated retinal vessels in deep capillary plexus at baseline which corresponded to the area affected by SRNVM. Fellow eyes of proliferative MacTel showed established disease stages on OCTA with progressive capillary crowding and entanglement of vessels likely corresponding to the future site of SRNVM.