Yes. Their eyes grow egg-shaped, a sloped retina like a horse's.

I'll try that next time honeydew starts repeating herself.

Seriously - of course it does. All our assumptions are based on
perpendicular angles of incidence.  All lenses distort, and all distortion
increases with angle, thickness, etc.

Curiously some people get used to a certain amount of distortion, then
complain if you take it away. Letters are "too sharp" or lines are "too
straight."

Panto tilt seriously impacts progressives, especially the width of
progressive channels. More tilt = closer = wider field. At the same time, it
might require more head/neck tilt to get an equivalent add.

-MT

Tilting the lens increases the power and induces cylinder equal to the sign of
the sphere with an axis of 180, if the vertical OC is not lowered .5mm below the
pupil per every degree of pantoscopic tilt.

Martin's formula for tilt

S'= S{1+(sin a)^2/(2n)}
C'= S'(tan a)^2

S sph power
S' new power
a tilt
n index of refraction
C' induced cyl

If your Rx is +8.00 DS, Trivex, with a panto of 15 and the OC is level with the
pupil, our eyes will see +8.18 +.59 x 180.

The idea is to keep the optical axis of the lens lined up with the rotational
center of the eye, important for medium to high  power lenses, and for all
aspherics. For the above example, one might reduce the panto to ten degrees, and
make sure that the vertical OC is positioned 5mm below the pupil either by
decentration, or by picking a frame that puts the 180 line 5mm below the pupil.

In addition to the above, the panto angle is desirable due to improved
perspective when looking down at floor, reduces the vertex distance on the down
gaze resulting in increased field of view with progressives, and simply looks
better because it follows the contour and structure of the face.

Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
Wauwatosa Wi.
~~~~~~~~~~~~~~~~~~
"Science is a way of trying not to fool yourself."
- Richard Feynman