Intraocular Lenses in Outer Space

What would be the best way to ship intraocular lenses (IOLs) and the other equipment needed for surgery into space for the potential needs of astronauts on a mission to Mars?

A new study by Morgan Micheletti MD and colleagues presented at the ESCRS Annual Congress in London considered how IOLs could best be packed, transported, stored, and protected from the space environment.

“I believe someone will need cataract surgery on Mars in my lifetime,” Dr Micheletti said. “A Mars transit can require almost a year—and returning to Earth for a vision-limiting cataract, injury, or other surgical eye problem may not be realistic. Eventually, treatment will need to happen where the patient is.”

Investigators on the JAMES project (Joint Assessment of Material Exposure in Space) flew 135 unpackaged IOLs to the International Space Station (ISS). The lenses were housed in special carriers called CLAIRE (Carrier for Lens Analysis in Interstellar Research Expeditions), which were mounted on three different locations on the exterior of the ISS. These positions included Ram, where the lenses were exposed to high atomic oxygen; Zenith, where the lenses were exposed to substantial ultraviolet (UV) from the Sun; and Underdeck, where the lenses were partially shielded from direct atomic oxygen and solar UV through their position under the exposure platform.

After approximately six months in orbit, the 135 flight lenses returned to Earth. The current analysis included 61 of those lenses and 20 of the 45 controls stored on Earth. Liliana Werner MD, PhD and her team at the Intermountain Ocular Research Center at the University of Utah, US, examined the lenses for overall clarity, how well the materials remained intact, and whether there were any deposits or changes on the surfaces.

Most of the lenses exposed to space conditions (42 of 61) showed no notable exposure-associated findings. The other 19 lenses demonstrated three principal patterns:

1. In the most directly exposed Ram tray, eight of the nine lenses showed cracks and localised surface roughening consistent with early atomic oxygen erosion. All eight were acrylic, including five hydrophobic and three hydrophilic lenses. The ninth lens was silicone and showed yellow discoloration.

2. Five space-exposed IOLs showed yellow discoloration, including two hydrophobic acrylic and three silicone lenses. Four were in the Zenith tray and one was in the Ram tray. Spectrophotometry showed lower light transmission, particularly between 400 and 500 nanometres.

3. All six space-exposed light-adjustable lenses, located in the three different positions on the ISS, showed a similar cobblestone or bubble-wrap appearance on both surfaces and along the optic edge. Neither of the two corresponding terrestrial controls showed that appearance. The mechanism remains unknown, and an explanation unrelated to direct space exposure cannot yet be excluded.

“This work matters now because these systems must be designed and validated long before the first patient needs them,” Dr Micheletti explained. “We cannot wait until someone is on Mars to ask whether the lens, equipment, and sterile supplies survived the trip.

“This was not intended to recreate how a packaged IOL would normally be shipped to Mars. The purpose was to identify potential failure modes under harsh exposure so we can begin designing better packaging, shielding, storage, and material selection strategies. Testing the lenses inside the ISS would not answer the same question because the interior is controlled and pressurised. We want to minimise packaging and, ideally, determine whether these products can be shipped without climate-controlled crew-cabin storage, because mass and volume carry significant costs.”

Morgan Micheletti MD, FACS practices at the Berkeley Eye Center, Houston, Texas, US.