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Re: Cat's eyes

People!

While everyone was on the subject of cats I forgot to mention some obvious fact about an aquatic mammal. The Calif. sea lion has a rather ingenious adaptation to sight for two very different
environments. We use our lens for focussing ~ 90% of the refraction occurring at the cornea, conversely the sea line has most of its refraction by the lens. It's rather large and spherical. So
what happens when it gets out of the water. With out the flat spot, ~ centered on its cornea, it would be grossly myopic. Cute no? A further refinement (a guess) is that since underwater not much
light, it probably has a rather sensitive retina. Above water it (day time) irises down, so most of the light enters through the flat spot.

bc


P.s. I used dental impression on both eyes while a sea lion was having a cataract operation, then used it as a mold for a dental plaster cast. Then used an opticians radius scope on the cast (after
coating it with grease to get quasi specular reflection).

Tom Ford wrote:

Okay, now we are getting somewhere. I like Leigh's later piece on this
thread and would like to add another datum, though it is even harder to
arrange than pickle jars.

In a second-story bathroom on Cape Cod, light from the window arrives over
the left shoulder while standing at the sink looking into the mirror.
Regardless of the absolute amount of light coming from outside, when the
mirror is "steamed up", as after a showerbath, one sees in the mirror just
a vague outline of the body shape but at the location of the two eyes (or
one if winking) patterns of concentric circles (10 or so) that alternate
light and dark as in an interference pattern. It looks like those goofy
glasses now in the marketplace, but the pattern continues until it runs out
of mirror. I was able to see this several times in a summer and for several
summers in a row until the house was sold. Direct sunlight was not coming
in the window. I had not thought of Leigh's pinholes, but I did think of
squinting and it did not alter the pattern, other than make it dimmer of
course. I made one attempt to photograph the effect, but that did not
capture what I saw, even with one eye, with the same clarity and contrast.
I knew what I was looking for in the photo but another would not have been
impressed. As the beads of moisture began to evaporate, one could see the
person better but the effect I describe began to fade. I am sure someone
will jump right in and show how this is related to the cat's eye
discussion, especially since Ludwig has mentioned his big circles -- that
is what prompted my recollection.

Tom Ford

At 11:55 AM 9/5/00 -0400, you wrote:
...
A convenient way to conducted cat's eyes experiments is
to be with the animal in a dark room and to use a flashlight.
In that way one can illuminate the face at various spots and
from various directions. Then one can replace the cat by a
human being and look for differences.

The glowing eyes of the cat are big circles, not single points,
as a reflection from a metallic sphere. They seem to disappear
from time to time. What does the cat do "to turn the glow off"?
Is it just closing the eyes, looking in a different direction or
something else? I wish I had time to play with this but the
school year just started. Perhaps others will report their
observations, as Doug did, and interpret them for us.
Ludwik Kowalski