One somewhat subtle marker with Seven is the size of whatever toy she is
moving.
 
Ashling gets especially inventive when she is more than just happy.  She
is also more inclined to play with the zoob tube then.
 
Glueball is looser abdominally (She tends to tighten those muscles when
tense.) and has fewer nightmares or no nightmares (She is prone to
nightmares and always has been.).
 
Scooter talks more, esp. his kissy murpph noises.
 
They all seem to have differences in their musk when optimally content,
and when way over the top there are great things like the pleasure
vibrations of dangling feet, kissing, and such.
 
Sherman plays cute less when content then when a tiny bit nervous, but
still plays cute.
 
Eyes: I don't know specifically.  Of course, vision problems in ferrets
are not uncommon and don't tend to matter much to them compared to other
senses.  I think that you many be thinking of past posts about worsened
eye problems with some color depletion syndromes.  I think that in both
the FML Archives
http://listserv.cuny.edu/archives/ferret-search.html
  and the FHL archives
http://fhl.sonic-weasel.org/
you may find posts from geneticist and genetics researcher, Brett
Middleton, and I also think that some vets (for some reason I think
Doctors Bruce Williams and Jerry Murray, but could be wrong) addressing
this question.
 
>I realized that there was one issue I did not address in my last
>positing about fit or fat ferrets and that was the area of competition.
>You heard me right... competition.  It seems that there is this unspoken
>competition on who has the biggest ferret amongst ferret people.  I hear
>it all the time.
 
Wow!  Great point, Betty!
 
>I think that we in the ferret community have to stop promoting heavy
>weights because it does have negative side affects.
 
YES!
 
Of course, larger frames do hold more weight and muscle is heavier than
fat so weighs more for less volume, but your point about too many obese
ones out there and the bad results of that is very valid.  To make it
worse, few of the ones who get dangerously heavy exercise enough.  In
human studies have shown that exercise can offset a lot of the effects of
having too much fat on a body, but many of these ferrets are getting too
much food and too little exercise and often that can also spell boredom.
Which, I guess brings up another subtle point; although we have some
ferrets who prefer to be couch potatoes, for may here improved levels
of muscularity can also be a subtle sign of well-being.
[Posted in FML issue 3958]