The eyes are gates that can be opened to good or to to evil, allowing an entrance into your life. The Bible speaks much about what we observe. For instance in the book of Proverbs 4:20-22:
20 My son, attend to my words; incline thine ear unto my sayings.
21 Let them not depart from thine eyes; keep them in the midst of thine heart.
22 For they are life unto those that find them, and health to all their flesh.
Jonah 2:8
8 They that observe lying vanities forsake their own mercy
Matthew 6: 22,23
22 The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light. 23 But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness!