NASA-sponsored study finds lengthy spaceflight can impair astronauts’ vision

SAN FRANCISCO, CA, Nov 03, 2011 (MARKETWIRE via COMTEX) — a brand new study sponsored by NASA finds that space flights lasting six months or more may cause a spectrum of changes in astronauts’ visual systems. Some problems, including blurry vision, seem to persist long after astronauts’ return to Earth. The consequences are affecting plans for long-duration manned space voyages, akin to a visit to Mars. The study team included ophthalmologists Thomas H. Mader, MD, of Alaska Native Medical Center and Andrew G. Lee, MD, of The Methodist Hospital, Houston, Texas. Their report is published in October’s Ophthalmology, the journal of the yank Academy of Ophthalmology.

The researchers studied seven astronauts, all of whom were about age 50 and had spent not less than six continuous months in space. All reported that their vision became blurry, to varying degrees, while at the space station. Vision changes usually began around six weeks into the mission and persisted in some astronauts for months after their return to Earth. Drs. Mader and Lee agree that the attention abnormalities seem like unrelated to launch or re-entry, since they occurred only in astronauts who spent extended time in microgravity.

In-depth examination of the seven astronauts revealed several abnormalities. All the subjects had a number of of the ensuing changes within the tissues, fluids, nerves and other structures at the back of the attention:

– Flattening of the back of the eyeball (five subjects);
– Folds within the choroid, the vascular tissue behind the retina, which is
the sunshine sensitive area behind the attention (five subjects); and
– Excess fluid around and presumed swelling of the optic nerve (five
subjects).

Such abnormalities could potentially be brought on by increased intracranial pressure — that’s, pressure contained in the head. However, none of those astronauts experienced symptoms usually related to intracranial pressure, reminiscent of chronic headache, double vision, or ringing inside the ears. Researchers believe other factors can be involved, inclusive of abnormal flow of spinal fluid across the optic nerve, changes in blood flow inside the choroid, or changes regarding chronic low pressure in the eye, that’s referred to as intraocular pressure. They hypothesize that these changes may end up from the fluid shifts toward the pinnacle that occur when astronauts spend extended time in microgravity.

The visual system changes discovered by the researchers may represent a group of adaptations to microgravity. The degree and kind of response seem to vary among astronauts. Researchers hope to find whether some astronauts are less suffering from microgravity and therefore better-suited to extended space flight, together with a 3-year round trip to Mars.

Of their report, Drs. Mader and Lee also noted a contemporary NASA survey of 300 astronauts that found that correctible issues of both near and distance vision were reported by about 23 percent of astronauts on brief missions and by 48 percent of these on extended missions. The survey confirmed that for some astronauts, these vision changes continue for months or years after return to Earth. The potential for near vision problems have been recognized for many years, and special “space anticipation glasses” to enhance visual sharpness were provided on all spacecraft dating back to John Glenn, who had a couple in his space capsule.

“In astronauts over age 40, like non-astronauts of a similar age, the eye’s lens can have lost a few of its ability to modify focus,” said Dr. Mader. “Within the space program’s early days most astronauts were younger, military test-pilots who had excellent vision. Today’s astronauts have a tendency to be of their 40s or older. This can be one reason we have seen an uptick in vision problems. Also, we suspect the various younger astronauts were likely to ‘tough out’ any problems they experienced, instead of reporting them.”

As a part of ongoing research all astronauts now receive comprehensive eye exams and vision testing. Diagnostic tests include pre- and post-flight magnetic resonance imaging, optical coherence tomography, which magnifies cross-section views of parts of the attention, and fundus photography, which records images of the retina and back of the attention. Intraocular pressure measurement and ultrasound imaging ensue in flight, in addition to pre- and post-mission.

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Concerning the American Academy of Ophthalmology The yankee Academy of Ophthalmology is the world’s largest association of eye physicians and surgeons — Eye M.D.s — with greater than 30,000 members worldwide. Eye health care is equipped by the 3 “O’s” — ophthalmologists, optometrists, and opticians. It’s the ophthalmologist, or Eye M.D., who can treat all of it: eye diseases, infections and injuries, and perform eye surgery. For additional info, visit www.aao.org . The Academy’s EyeSmart(R) public education program works to coach the general public concerning the importance of eye health and to empower them to maintain their healthy vision, by providing essentially the most trusted and medically accurate details about eye diseases, conditions and injuries. Visit www.geteyesmart.org to benefit more.

SOURCE: American Academy of Ophthalmology