naked eye definition by American Heritage Dictionary
nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The eye unassisted by an optical instrument.
naked eye - Phrases/Idioms
Sight unassisted by an instrument such as a microscope or telescope. For example, These insects are too small to be seen with the naked eye. This expression was first recorded in 1664.