Some Corneal
Shapes Work Better than Others
The lens in your camera, if it's
one of the better ones, will have what we call an aspheric
shape. We have learned that this shape produces a sharper
and clearer image than if the lens surface was circular.
Basically, to make the best image possible, a lens should
be steeper in the centre, and flatter towards the edges.
This optically improved lens has
what we call a prolate shape, and can
be thought of as resembling a bullet tip.
The opposite shape, with correspondingly poorer optics,
is called oblate and looks
like a burger bun.
As shown in the following figure,
the human cornea has been modified in order that we
can see better, and reduce the optical problems that
a circular lens creates. Evolution has changed our eye
surface from a circle into an prolate aspheric curve.
The eagle takes this improvement even further, hence
the expression 'eagle-eyed'. The poor frog has an oblate
'burger bun' cornea, and the term 'frog-eyed' would
be no compliment to the quality of your sight!
CK changes the shape of
your cornea in the direction of that of an eagle,
and will double the depth of field compared
to a normal human eye. Unfortunately, standard
laser treatment for short-sight or myopia will flatten
the central part of your eye and move the optics in
the direction of the frog. The loss of quality of vision
will be particularly noticeable at night and in low
light conditions. To help reduce this problem, newer
lasers and wavefront guided treatments are designed
to minimize the loss of the prolate, bullet shape of
your eyes. CK by design (as shown below) will improve
the spherical optics of your vision, by steepening the
central area, and simultaneously flattening the cornea
further out - eagle eyes!
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Your
choice of surgeon will be the most important factor
for your eye treatment. Download our free guide now.
Meet
patients who have had laser eye vision treatment or
the CK read-again without-glasses correction? Click
on the image or the link below to see these videos.