I'm pretty sure that a lens was not inserted.  In most cases in animals,
the defective lens is removed, rendering the animal able to see, but
vision is limited to light and dark, shapes and shadows, and a limited
range of vision (but if you are totally blind, it does make all the
difference in the world.)  I'm pretty darn sure that there are not any
ferret lenses developed out there just yet.
 
With kindest regards,
Bruce H. Williams, DVM, DACVP
 
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[Posted in FML issue 3439]