VISION QUEST
CU faculty members study impact of spaceflight on eyes
By Toni Lapp
October 2024
During SpaceX’s Polaris Dawn's multi-day high-altitude mission in September, the crew conducted research to better understand spaceflight-associated neuro-ocular syndrome (SANS). Riding along with them was the equipment and expertise of Prem Subramanian, MD, PhD, chief of neuro-ophthalmology at the University of Colorado School of Medicine.
Subramanian and CU Boulder aerospace engineering associate professor Allie Hayman, PhD, sent up specialized optical equipment to gather data from astronauts’ eyes during and after the five-day mission.
“This project is an amazing collaboration with astronauts forging the way for deep space exploration,” Subramanian says. “It’s the first time we can get dynamic information on how the body reacts to the transition to spaceflight.”
EYES ON THE SKIES
Astronauts have noticed vision changes during long-duration space missions. Since 1998, NASA has sent astronauts to the International Space Station with “space anticipation glasses,” which have adjustable refraction settings to meet changing vision needs, similar to binoculars. In 2011, NASA began conducting MRI scans on astronauts following missions, which revealed potentially increased pressure in their brains as well as optic disc swelling, or papilledema, in more than half of the astronauts.
Prem Subramanian, MD, PhD"We’re trying to figure out what’s causing these eye changes,” Subramanian says. “We’ve backed off from the idea that it’s necessarily caused by elevated pressure in the head. One of the theories is that it may be a balance between intraocular pressure and intracranial pressure, or even pressure in the blood vessels that alters fluid dynamics in the eye socket, or orbit. All of those things are probably interacting to cause this problem.”
Subramanian sent up SENSIMED Triggerfish lenses, which are “smart” contact lenses to track eye pressure fluctuation and changes in cornea dimensions in glaucoma patients. CU Department of Ophthalmology adjoint professor Kaweh Mansouri, MD, helped develop these lenses, which monitor astronauts’ eyes during launch and as they transition to microgravity.
The lenses contain sensors that transmit data to an antenna and local storage device, enabling Subramanian to collect and analyze data upon their return. The team is also sending a device called the QuickSee, to measure the shape of eye changes.
“We’re looking for changes in the axial length of the eye, because we know that the eye gets a little shorter when you go into space,” Subramanian explains. “We're trying to get more concrete data on which layers of the eye are changing because that helps us understand what could be driving the optic nerve swelling.”
Subramanian has been involved with the space program since 2013, after he delivered a lecture at a NASA meeting on papilledema. In 2014, he was named to the National Academy of Medicine’s Committee on Aerospace Medicine and the Medicine of Extreme Environments, a position he continues to hold.
Hayman has developed techniques to monitor intracranial pressure non-invasively by measuring signals from the inner ear. She and Subramanian also have worked together to study the use of artificial gravity—with a short radius centrifuge—as a means of treating or preventing SANS.
EYE CONDITIONS ON EARTH
Subramanian says studying SANS could improve care for people on Earth with idiopathic intercranial hypertension, which leads to optic nerve swelling and can result in permanent vision loss. The study improves understanding the biology of the eye and orbit, how variations in blood flow affect the eyes and vision, and why people on Earth get elevated intracranial pressure.
“Solving this problem can also help us advance deep space exploration,” Subramanian says. “SANS is considered by NASA to be the No. 2 hazard behind radiation exposure that will need countermeasures for humans to pursue long-duration spaceflight.”
“It’s gratifying to be able to participate in research like this,” he continues. “It is an acknowledgment of the longstanding expertise we have at the University of Colorado, in ophthalmology as well as aerospace medicine. And it’s a recognition of the strength of collaboration between the institutions that make up CU.”