OCT-Diagnostics of Optic Nerve Disc Edema in Space Flight. Analysis of the Retina, Optic Disc and Neuroretinal Circle Thickness

The article analysis the state of 24 eyes of 12 Russian cosmonauts who made long-term space flights to the ISS in the period from 2016 to 2021. The analysis was carried out by HRA and OCT images study, using the Display function included in the program of Spectralis OCT device. The thickness of the optic nerve head and retina was determined according to the hourly meridians, which allowed us to accurately diagnose and classify the optic disc edema according to the stages of the Frisen scale. By measuring the percentage ratio of the maximum thickness of the nerve disc within its boundaries to the minimum thickness of the retina outside the boundaries of the disc, we determined the digital value of prominence in each temporal hourly meridian, limited by the temporal sector of 95°. The presence of prominence in the extreme temporal meridians, or its absence at all, we regarded as a physiologically healthy state of the optic disc, corresponding to stage 0. This stage was established in 13 eyes (54.2%). Stage I (7 eyes (29.2%)) was diagnosed based on the absence of prominence in the horizontal temporal meridian. The defining feature of stage II is an increase in prominence in the temporal horizontal meridian by more than 10%. Subclinical stage II (prominence is increased, but less than 10%) was diagnosed in two eyes of two cosmonauts (8.3%). Clinically pronounced papilledema II–III stages was diagnosed in two eyes (8.3%) in one cosmonaut, where the maximum value of prominence was 70.1% in the right eye, and on the left – 40.1% in the horizontal meridian. The study shows that an increase in prominence up to 70% in the temporal horizontal meridian at stage III of edema leads to neurodegeneration of the optic nerve fibers in space flight. At stages II–III of edema, an increase in the minimum thickness of the neuroretinal rim compared with all other observations. At 0 – II subclinical stage, according to this indicator, it was impossible to differentiate the state of the optic disc.