Special Senses: The Eye and Vision

Which structure in the eye is responsible for most of the light refraction as light enters the eye?

A patient presents with blurry vision when looking at distant objects, but can see nearby objects clearly. Which condition is most likely present, and what is the underlying anatomical cause?

Which equation best describes the relationship between the focal length ($f$), object distance ($d_o$), and image distance ($d_i$) for the eye's lens?