There's a quite good article here about the human vision system in comparison with photographic ones.
The human vision system is not complete considering only a lens and a retina. Your vision is highly interpreted by your brain, and for this reason you can't make direct comparisons.
From long experience the focal length generally used to produce a field of view and perspective that is "comfortable" for humans is the 50mm focal length combined with a "full frame" sensor. Some people prefer the 43mm focal length as it is a perfect normal for the full frame sensor. On crop frame 28mm is roughly equivalent to 43mm, and 35m is generally considered a reasonable choice for a this purpose. But human vision has quite different properties for a 2D image and this does not work perfectly.
This question deals with the same problem and you'll see how contentious this all is from the answers and comments.