Cataract surgery will be needed in space, surgeon predicts

Cataract surgery will be needed in space, surgeon predicts Gaby Clark Scientific Editor Robert Egan Senior Editor An eye surgeon with a passion for space since childhood predicts that as astronauts start to make journeys to the moon and Mars in the near future, eye surgery in space will eventually become a necessity. Dr. Morgan Micheletti from the Berkeley Eye Center, Houston, Texas, U.S., told the 44th Congress of the European Society of Cataract and Refractive Surgeons (ESCRS) today (Sunday) that cataract surgery, in particular, will be needed as people travel through space and stay in space stations for longer periods of time. Therefore, it was vital to know how medical supplies such as intraocular lenses (IOLs) and the other equipment needed for surgery could best be packed, transported, stored and protected from the space environment. To investigate this, he sent IOLs made of different materials into space as part of the Joint Assessment Of Material Exposure In Space (JAMES) project. "I believe someone will need cataract surgery on Mars in my lifetime," 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. "Astronaut candidates do not need perfect uncorrected vision, and refractive correction or certain prior refractive surgeries can be compatible with selection. More importantly, good vision at launch does not prevent aging, radiation exposure, injury or disease later. As human spaceflight expands beyond career astronauts, the traveler population will also become more diverse. "This work matters now because these systems must be designed and validated long before the first patient needs them. We cannot wait until someone is on Mars to ask whether the lens, equipment and sterile supplies survived the trip." Testing lenses outside the ISS The JAMES project flew 135 unpackaged IOLs to the International Space Station (ISS). They were placed in special carriers situated in three different locations on the outside of the ISS. The carriers were called CLAIRE (Carrier for Lens Analysis in Interstellar Research Expeditions), and the three positions on the ISS were 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 by being mounted under the exposure platform). "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 pressurized. We want to minimize packaging and, ideally, determine whether these products can be shipped without climate-controlled crew-cabin storage, because mass and volume carry significant costs," Micheletti said. On Earth, 45 IOLs were removed from their original packaging and placed in a carrier similar to those for the space lenses, called WILLIAM (Worldly Interface for Lens Logistics and Integrated Astronomical Monitoring). These IOLs remained on Earth at room temperature and atmospheric pressure to act as controls. 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: 81 lenses in total. Dr. Liliana Werner and her team at the Intermountain Ocular Research Center at the University of Utah, U.S., examined them for overall clarity, how well the lenses' materials remained intact, and whether there were any deposits or changes on the surfaces. Three patterns in damaged lenses Most of the lenses (42 of 61) exposed to space conditions showed no notable exposure-associated findings when analyzed. The other 19 lenses showed three principal patterns: - In the most directly exposed Ram tray, eight of the nine lenses showed cracks and localized 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. - 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 nanometers. - 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. Micheletti stressed that this was an exploratory, descriptive study and was not intended to compare different makes or types of lenses, or to test a hypothesis. The analysis covered a selected subset of the payload. Sample sizes were small and uneven, and in some positions in the carriers there was only one lens of a given model. The lenses were deliberately unpackaged, and handling or environmental contamination could not be fully excluded. The control lenses did not undergo launch, return or flight handling, which limits attribution of the changes specifically to external exposure. Beyond transmission spectrophotometry, image-quality, mechanical and clinical-performance testing has not yet been completed. He said the findings should not be used to rank manufacturers or lens models and do not imply a safety concern for routine cataract surgery on Earth. Micheletti said, "The findings suggest that lens material and exposure location may influence the changes observed. Packaging, shielding and storage were not compared in this experiment and are the next protective strategies we need to test. The engineering challenge will be providing enough protection without adding unnecessary mass because every kilogram sent into space carries a cost." A stepwise path to surgery He hopes to investigate how a phacoemulsification system, the ultrasound and fluidics system used in cataract surgery, performs during the brief periods of microgravity produced by parabolic flights. If that work is successful, the longer-term path could include sustained microgravity testing and, eventually, an in-orbit surgical experiment. "The progression has to be deliberate: first the materials, then the equipment, then the procedure and, ultimately, the surgery. My long-term hope is to help make the first eye surgery beyond Earth possible," he said. "I have been fascinated by space for as long as I can remember. In second grade, I did a project on the Apollo missions and had the opportunity to interview Gene Kranz, the NASA flight director best known for his leadership during Apollo 13. That experience stayed with me. Once I became an eye surgeon, that fascination evolved into a more practical question: could I perform surgery in space?" What JAMES set out to answer Published clinical reports have described astronauts and other spaceflight participants who flew with implanted lens devices. Those implanted devices were protected by the eye and body. What had not been studied before was how multiple modern IOL materials respond when directly exposed outside the ISS to vacuum, temperature cycling, solar ultraviolet radiation, ionizing radiation and atomic oxygen. JAMES addresses preimplantation transport and storage, not the performance of an IOL already implanted in an eye. To the investigators' knowledge, JAMES is the first controlled experimental study to expose multiple modern IOL materials directly to the external low-Earth-orbit environment outside the ISS and return them for laboratory analysis. Dr. Joaquín Fernández, ESCRS secretary, CEO of Qvision and medical director of Andalusian Ophthalmology Institute at Vithas Hospitals, Almería, Spain, who was not involved with this research, said, "As more and more people go into space and for longer periods of time, it is likely that eye surgery will be required at some point. Therefore, it's imperative that we understand how lenses and other materials required for surgery behave when exposed to environments beyond the Earth's atmosphere. The research presented today is forward-thinking and will undoubtedly play an important role in our preparations for deep space exploration." Provided by European Society of Cataract and Refractive Surgeons