While i don't know the exact reasoning, or if this is the case I have noticed on my muttface (he really is a mutt of some kinda black/tan terrier thing) he is kinda "balding" around the eyes when they water a great deal. It's a concern i have as well, but at the same time, i notice it flux of hair loss vs it being there, when his eyes are more leaky then when they are not. He could very well have allergies which are causing this issue.
I don't think it's much to worry about physically though. I would say try to keep the eyes clean and if they water or leak make sure you get that off asap. but no worries over all.
**additionally, your pup, if he has allergies may be rubbing his/her face which is causing the hair-loss as well. If this is the cause, if you noticed licking or chewing, try giving them 5mg (usually a 1/2 tab) of loratidine aka claritin, or Zyrtec aka cetirizine (also 1/2 tab = 5 mg) or a low dose of benadryl(25mg cap), though keep in mind that all 3 will make your tiny pup very sleepy, and will probably knock them out for a while.
no barking if nothing else!