Refractive Display Mode - OCULUS Easygraph 70620 Instruction Manual

Page 40
The refractive display mode permits an assessment
of the optical effect of the corneal surface. For this
purpose it uses focal distances rather than curvature
values. These focal
according to Snell's law (light-ray tracking), and
spherical aberrations have therefore already been
taken into account. Focal distances are always given
in terms of diopters.
The difference between this and the conventional
curvature display method becomes apparent when
one considers the topographic images they produce
of a sphere:
The curvature map ("Original", at the top right) will
only show one color, since the curvature of a sphere
is everywhere the same.
Instruction Manual Easygraph

7.5.2.7 Refractive Display Mode

distances are calculated
In the refractive map (bottom left ) the diopter values
are greater at the periphery because the focal
distance at the periphery (f
the center (f ) (spherical aberration).
1
f f f
1 2 3
, f ) differs from that at
2 3