Both LASIK and PRK Have Been Approved by NASA for Space Flight. A New Study of the Effect of Spaceflight on a NASA Astronaut with PRK Laser Eye Surgery Confirms PRK Was Safe, Effective, and Well Tolerated in Space. In my previous blog, we looked at the effects of very high altitude on LASIK laser eye surgery — high elevation sometimes experienced by the most advanced mountaineers in extreme circumstances such as climbing Mount Everest.

A recent study, however, looked at the performance of PRK laser vision correction in the highest altitude of all — outter space! The results were quite reassuring, even for those of us who will never go higher than Mammoth Mountain.

Recently, both LASIK and PRK laser eye surgery were approved as forms of vision correction for space flight by NASA. This study looked at the visual performance in space of a 47 year old NASA astronaut (Richard A. Garriott) who had undergone PRK laser eye surgery nearly 14 years prior. The astronaut went on a 12 day Russian Soyuz mission to the International Space Station and back.

The extreme conditions of launch, microgravity exposure in space, and reentry create demanding conditions for the eye after PRK surgery. It turns out that the confined environment and poor lighting in the Russian Soyuz spacecraft additionally creates a visually demanding environment for the astronaut’s eyes after PRK. Despite all this, the astronaut’s PRK vision performed extremely well.

On liftoff in the Soyuz spacecraft, G-forces reach +3 to +4 Gx for 10 minutes. These extreme G-forces push the eye backward and then resolve as the astronaut enters space. There is a corresponding rush of between 1.5 and 2 liters of blood towards the head, which results in a rise in intraocular eye pressure and facial swelling. During orbit on the International Space Station, the eye is exposed to a microgravity environment, which creates a complex set of new circumstances for PRK to contend with. During descent, the Soyuz reaches a G-force deceleration of +4 to +5 Gx.

The astronaut’s vision was measured during spaceflight and he also was asked to fill out a daily questionnaire about his vision. Compared to his baseline vision, there was no change in vision either while in orbit on the International Space Station or when back on Earth after the conclusion of the mission. Lens measurements of his vision showed no shift toward farsightedness, but possibly a minor shift toward nearsightedness. On the questionnaire, the astronaut reported he had a “little” trouble with “tired eyes” and “slight” symptoms of “irritated and painful eyes” during the space flight. No problems with vision were reported at any time, including no report of visual fluctuation, blurry vision, dim light problems, or halos around lights. The astronaut was asked to look out of a porthole at night at the brightest star he could find to see if he could detect any ghosting, doubling, flare, rays, or halos coming off the star. None of these occurred at any time. No reduction of any sort in visual performance was noted during spaceflight.

Unrelated to his previous PRK laser vision correction eye surgery, the astronaut did notice several instances of multiple pixel-like bright light flashes while in space. These specific types of spontaneous visual flashes were noted by Apollo astronauts who had not previously had any form of eye surgery and are thought to be due to radiation energy traveling through space being perceived by the retina.

In the end, PRK proved itself to be a very good alternative to glasses and contacts. Glasses pose dependability problems in the microgravity environment of space and contacts are particularly concerning as a contact lens infection would be very difficult to treat so far from home! This study shows that in space, as on Earth, laser eye surgery can often be the best vision correction choice for a challenging ocular environment.

See Also

The International Space Station Flight of Richard Garriott

Visual Stability of Laser Vision Correction in an Astronaut on a Soyuz Mission to the International Space Station

Refractive Surgery Safety at Altitude

Optic Disc Edema, Globe Flattening, Choroidal Folds, and Hyperopic Shifts Observed in Astronauts after Long Duration Space Flight

Publications and Presentations of the Ophthalmology Branch, USAF School of Medicine

NASA Study of Cataracts in Astronauts

Laser Refractive Surgery in the United States Navy

Past, Present, and Future of Corneal Refractive Surgery

NASA Approves Advanced LASIK for Use on Astronauts

NASA Approves LASIK for NASA Astronauts (video)