Retinal Vascularity in Military Pilots in Relation to the Type of Aircraft, Flight Altitude and Total Hours of Flight

<b>Background</b>: The aim of the study was to assess retinal circulation in military pilots, as well as to determine the relationship between the type of aircraft, flight altitude, total hours of flight time and parameters of retinal circulation, using OCT angiography (OCT-A). <b>Methods</b>: This cross-sectional study enrolled 44 military pilots and 44 controls. The inclusion criteria encompassed healthy adult men. Due to the fact that military pilots cannot suffer from any vision defects or any other eye disease, the exclusion criteria concerned the control group and included refractive error exceeding -3 diopters (D) and +3 D and concomitant eye diseases, such as any retinal or choroidal pathologies, glaucoma, uveitis. The exclusion criteria for both groups were low-quality OCT-A images. Subsequently, the results of the measurements obtained for 176 eyes were included in further descriptive and multivariate analyses, of which 88 were in the pilot group versus 88 in the comparison group. <b>Results</b>: The total vessel density in superficial and deep capillary plexuses was significantly decreased (<i>p</i> = 0.0176, <i>p</i> < 0.0001, resp.) the longer the flight experience, particularly in the parafoveal region (<i>p</i> = 0.0299 and <i>p</i> < 0.0001, resp.). Moreover, the foveal avascular zone area was significantly increased proportionally to the total hours of flight (<i>p</i> = 0.0083). Also, the total vessel density was increased with a higher flight altitude in the deep capillary plexus (<i>p</i> = 0.0042), especially in the parafoveal region (<i>p</i> = 0.0110). <b>Conclusions</b>: Gravitational forces manifesting in the unique conditions of the flight of military pilots seem to induce microvascular changes in the retina.