Question "…He loses his balance, I was thinking because of his failing eyesight or there is more to it?"

Answer: There are many possible causes of balance problems, but yes the eyes play a big part.

 

• As was mentioned in the last blog entry (for someone else with vertigo). The system that gives you balance is a complicated one. Many different sensory factors are taken into account by your brain and interpreted to let you know where you are in the world. The last blog entry concentrated on the middle ear part of balance. That is a big part. However, the two other big parts are your vision and nerves in your limbs, especially your feet and legs (proprioception).  
• As you know, uncontrolled diabetes ruins your eyes. Unfortunately, diabetes also ruins the peripheral (nerves in your feet). So with bad diabetes, you are only working with 2/3 or the normal balance system. Working with 1/3 is hard enough. For example, as a normal person, try keeping your balance on one leg with your eyes closed. It’s hard. That is only removing one part of your balance system (your eyes). In this scenario your leg nerves and your semicircular canals are trying to figure it out on their own. Now imagine you take away another factor… No eyes and no feet nerves... very hard to keep balance.  
• Of course there are other potential causes for balance problems. However, for this person I would think that diabetes is a big factor.
• Regardless, see your doctor to make sure that there is nothing else going on.