I have sat silent through most of this but I gotta stick my 2 cents in.
When do kits eyes open?  Granted I have only been breeding 2 years... but I
have to agree with the comments made by the Killians.  On average, all my
litters have opened their eyes in the later part of the 4th week or early
into the 5th week.  There have been a few exceptions, and I have seen
*slit* openings as young as 2 weeks but they never actually fully opened
until the 4th-5th week.  I did research quite a lot and talked at length
with several breeders before I started breeding and still do... it has
always been my understanding this was the normal time frame.  Three of the
ferret books and one vet medical book I have which cover breeding all state
that a ferret kit's eyes commonly open in the fourth to fifth week.  I
almost got the feeling there was a bit of an attitude of "my kits are
better than your kits" based on what age the eyes opened.  It's a simple
matter of natures timing and has nothing to do with a kits (or the
breeders) quality.
 
Eye infections common?  It seems to be somewhat common for kits to develop
conjunctivitis.  More than one vet has told me it is common not only in
ferrets, but also in puppies and kittens... something to do with the
opening process and tear ducts getting clogged.  Doesn't happen in every
kit but usually about 1/3 or so get at least a mild case.
 
Again, it's a simple matter of the process and tear ducts etc and not a
reflection on the abilities of the breeder or their care of the kits.
[Posted in FML issue 3025]