The cosmonauts were given different test tables for determining the acuteness of eyesight , the possibility to distinguish colours and to switch eyesight from one object to another while in flight.
ОСТРОТА ЗРЕНИЯ
Русско-английский перевод ОСТРОТА ЗРЕНИЯ
Русско-Английский словарь идиом по космонавтике. Russian-English dictionary of idioms on cosmonautics. 2012