Abstract
Purpose:
To evaluate effects of low Earth orbit (LEO) space conditions on intraocular lenses (IOLs) manufactured from different materials.
Setting:
International Space Station (ISS); Intermountain Ocular Research Center (John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA).
Design:
Experimental study.
Methods:
135 IOLs made of hydrophobic acrylic, hydrophilic acrylic, and silicone materials were launched to the ISS as pressurized cargo. Of these, 61 were analyzed. On the ISS, the IOLs were placed in 3 external locations, differentiated by their exposure conditions: Ram (high atomic oxygen flux), Zenith (filtered UV-channel exposure), and Underdeck (external ISS environment with partial shielding). 45 corresponding controls remained on Earth. Of these, 20 were analyzed. After 6 months, the flight IOLs returned to Earth; 61 flight IOLs and 20 controls underwent gross and light microscopy. Changes were further assessed through scanning electron microscopy coupled with elemental analyses or spectrophotometry.
Results:
Post-mission analysis of space-exposed IOLs demonstrated changes consistent with polymer erosion in 5 hydrophobic and 3 hydrophilic acrylic IOLs. 2 hydrophobic acrylic and 3 silicone lenses demonstrated yellow optic discoloration with changes in light transmission. These IOLs were all in the tray closest to exposure to Ram or Zenith conditions. All 6 space-exposed light-adjustable lenses (LALs; RxSight) in the 3 locations, with or without ActivShield, exhibited similar “cobblestone” changes on the anterior and posterior optic surfaces, as well as the optic edge.
Conclusions:
This exploratory study showed that IOL materials may differ in susceptibility to environmental hazards in LEO. These findings may inform packaging, shipping, and storage of IOLs in space, as ophthalmic care will be required for future long-duration space missions and eventual extraterrestrial habitation.