Abstract
The authors of this experimental study sought to test the operational effects of scopolamine and dexamphetamine by testing near vision, accommodation, and pupil size. Scopolamine (0.4 mg) and dexamphetamine (5 mg) has been used as an oral medication to treat motion sickness. With a peak onset of 1 hour, the scopolamine improves symptoms of nausea while suppressing the parasympathetic nervous system. Side effects include drowsiness, which is opposed by the dexamphetamine, cycloplegia, and mydriasis.
In this study, 131 subjects were tested before and after medication. These subjects underwent near vision tests with a miniaturized Snellen chart and accommodation testing with a Prince rule. All of the subjects took the medication prior to a parabolic flight that simulated zero gravity and were tested after flying 40 parabolas. Parabolic flight is a provocative flight pattern where a passenger jet flies in a parabola that lasts approximately 45 seconds from one inflection point to another, thereby permitting free-fall. Comparison data were collected 3.7 hours after the initial dose.
Though there was a statistically significant increase in pupil diameter after flight from 5.3 mm to 6.4 mm, there was no significant difference in accommodation or visual acuity. The authors suggested that the visual side effect profile of these medications did not present an operational impediment. This study was limited because 38% of their patients did report motion sickness and a placebo group without medication or without flight was not used to delineate the effects of drugs or parabolic flight.
(Aviat Space Environ Med. 2011;82:683–688). AL Markowski, K Lindren, JP Locke.
Prepared By Anil Menon, MD, UTMB/NASA Aerospace Medicine Fellow, Galveston, TX, USA