I just returned from the vet with the kitten (who I have decided to
call Trinity), who is 3 and 1/2 weeks today. She is very underweight
(5.1 oz, she should be 9-11 oz).  The good news is that she doesn't
have an infection, but for some reason, one eye is open, her other eye
has not developed as quickly as it should.  It may continue to
develop, but she will probably be blind in one eye. The vet said that
she has very soft joints, her ear canals (?) are not developed but he
couldn't say why.  She may be simply slow to develop, or have a birth
defect that is undetectable at this age.  She is able to see and
follow movement and can hear well enough to orient to my voice and
find me when I place her on the floor.
 She is otherwise healthy, with a good appetite, the vet wormed her
and we hope that she will begin to gain weight.  Does anyone have any
ideas, perhaps encountered this before? I would like to know if there
may be other problems associated with this that I should look for.
Alas, the vet said that though she is healthy, she may still not be
strong enough to make it, and he doesn't want to give her any shots
until 6 wks because she is so small.
 I want to thank everyone for their advice and concern, and I will
keep updating with anything new.