裸眼

1. Origins, structure, and basic meaning

• Structure: 裸眼（らがん） means the eyes without vision correction from glasses or contact lenses.
• Basic usage: 裸眼ではほとんど読めない describes difficulty reading small print without correction; 眼鏡を外し、しばらく裸眼で describes the state after removing glasses.

2. Common pitfalls and similar expressions

• Observation tools versus vision correction
  • 肉眼 focuses on seeing directly without an observation tool such as a microscope. 裸眼 focuses on the absence of correction by glasses or contact lenses, so the basis of the contrast differs.
• The state of seeing without correction
  • In the example, 裸眼で highlights the state of seeing without vision correction rather than simply identifying the means of observation. The preceding act of taking off glasses makes this meaning clear.