Spaceflight Associated Neuro-Ocular Syndrome as a Potential Variant of Venous Overload Choroidopathy

Abstract

Introduction: Novel ocular findings have been identified in spaceflight. We discuss their potential association with Spaceflight Associated Neuro-ocular Syndrome (SANS) and integrate them in a framework that may help explain the pathophysiology.

Methods: We reviewed literature using the Medline/PubMed database starting in October 2020. Search terms included ocular circulation, hyperopia, serous chorioretinopathy, pigment epithelial detachment, choroidal folds, choroidal thickening, pachychoroid disease, optic disc edema, venous overload choroidopathy. No date exclusions were placed on the search. Articles were reviewed for relevance. Articles relevant to the pathophysiology of choroidal thickening and choroidal venous overload as it applies to SANS were included.

Results: Terrestrial venous overload choroidopathy is thought to be due to impediment to choroidal venous outflow, resulting in dilation of choroidal veins, increased choroidal thickness, pigment epithelial detachments, and serous detachment of the retina. Serous detachment of the retina, pigment epithelial detachments, choroidal folds, and thickening of the choroid were identified on in-flight optical coherence tomography testing. Postflight findings include these, as well as globe flattening. During spaceflight, there is a cephalad displacement of both blood and cerebrospinal fluid. This may lead to pathological consequences in the eye. Remodeling of the choroidal venous vortex system may result in continuance of pathophysiological findings after return to Earth, suggesting the best strategy is prevention.

Discussion: Microgravity induced venous overload of the choroid may play a role in SANS pathophysiology, and a venous overload choroidopathy may help explain several SANS features that remain unexplained by an etiology of elevated intracranial pressure. Mampre D, Spaide R, Mason S, Van Baalen M, Gibson CR, Mader TH, Wostyn P, Briggs J, Brown D, Lee AG, Patel N, Tarver W, Brunstetter T. Spaceflight-Associated Neuro-ocular Syndrome as a potential variant of venous overload choriodopathy. Aerosp Med Hum Perform. 2025; 96(6):496-508.

Keywords: SANS; Spaceflight Associated Neuro-ocular Syndrome; astronaut; optic disc edema; pachychoroid; pigment epithelial detachment; serous chorioretinopathy; venous overload choroidopathy.