It has long been known that astronauts who travel to space for prolonged duration return to Earth with changes to the structure of their eyes that could ultimately impact their vision and while this has been studied by NASA for a long time, a University of Houston optometrist has quantified some of the changes using optical coherence tomography imaging.
The phenomenon is called space flight-associated neuro-ocular syndrome (SANS) and now the latest study by UH optometrist has been published in JAMA Ophthalmology. The study is based on pre-flight and post-flight data from 15 astronauts who had spent time aboard the ISS with changes detected in morphology of the eyes.
Nimesh Patel, assistant professor at UH said that while all of them had good vision before and after the flight, some of the astronauts had suffered from change in structures of their eyes.
For the research Patel created customized programs to study data from optical coherence tomography that enable us to take noninvasive cross-section pictures of the retina. His algorithms showed that following prolonged space flight, three major changes occur. The analysis of the data indicates that when astronauts are exposed to microgravity for long duration, there is a change in the position of the Bruch membrane opening, an increase in retinal thickness closer to the optic nerve head rim margin, and an increase in the proportion of eyes with choroidal folds.
While some of these changes would be expected in patients with elevated intracranial pressure, there are also significant differences. For example, choroidal folds are not as prevalent in individuals with intracranial hypertension.
Although the exact cause remains unknown, it is hypothesized that the changes seen in astronauts are a result of microgravity-associated orbital and cranial fluid shifts.
Because some astronauts included in the study had previous spaceflight experience, the preflight data was first compared with healthy control subjects before comparisons with postflight scans.
“The results of these investigations suggest that, although there may be resolution of structural changes, there could be long-term ocular anatomical changes after extended-duration spaceflight,” said Patel.
He hopes his findings will one day have applications for patient care.