Microvascular changes precede visible neurodegeneration in fellow eyes of patients with asymmetric type 2 macular telangiectasia

IMPORTANCE: Macular telangiectasia type 2 (MacTel) is bilateral disease with characteristic alterations of the macular capillary network along with decreased macular pigment in the parafoveal area. The purpose of this study was to highlight that some eyes show microvascular changes which precede any visible neuronal changes on spectral-domain optical coherence tomography (SD-OCT). METHODS: This observational study was conducted at a tertiary eye institute. From a registry of 630 patients with MacTel, we identified 4 patients with typical MacTel characteristics in only one eye with no visible changes on colour photographs or SD-OCT in the fellow eye. These 4 patients had findings of MacTel documented by colour fundus photograph, multicolour imaging (MCI), fundus autofluorescence (FAF), confocal blue reflectance (CBR), SD-OCT, and OCT-Angiography (OCT-A) in one eye. OCT-A was performed in MacTel patients using the High-resolution Spectralis (Heidelberg Engineering) module with a full-spectrum probabilistic approach and we employed a 30 degrees x 15 degrees (similar to 8.8 mm x 4.4 mm) scan pattern covering the macula. MCI was done at the end so as to avoid fading the confocal blue reflectance hyperreflectivity seen in MacTel. RESULTS: On OCT-A, all 4 fellow eyes showed telangiectasia and foveal avascular zone changes in the superficial and deep capillary plexuses with no changes on SD-OCT. None of the eyes showed typically increased reflectance on CBR around the foveal area. CONCLUSION: These findings show that microvascular changes on OCT-A may occur before visible neurodegenerative changes on OCT, providing new insights into the course of the disease.