Re: sclerotic rings

[dennis.waddington@geofuel.north.net (Dennis Waddington)]

Mickey Rowe <rowe@lepomis.psych.upenn.edu> answered earlier:

MR>Nicholas Roy Longrich <longrich@phoenix.Princeton.EDU> writes:

MR>>       On the subject of eyes, I recall that some birds have a pair

[interesting stuff deleted mainly concerning specialized eye structures
for multiple/specialized vision purposes]

MR>the retina looks like every other).  The animals I've been studying
MR>(green sunfish, _Lepomis cyanellus_; yes, that's how this computer was

Which leads me to ask a possibly naieve question that first occurred to
me when I first wore some of the very thin, very soft type of contact
lenses. Some (modern) avian, reptilian and amphibian (?) species have a
clear nictitating membrane, or third eyelid, commonly described in the
few layman's sources I've stumbled across as affording protection for
the surface of the eye. Can anyone can say whether additionally it has
any optical properties such as distance or closeup enhancement? Or is it
totally neutral optically?  Just wondering.

Thanks ... Dennis Waddington
dennis.waddington@geofuel.north.net
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