home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Contact Lens Series
/
Contact Lens Series Volume 1.iso
/
pc
/
topogc.dxr
/
00034_Field_34.txt
< prev
next >
Wrap
Text File
|
1997-10-28
|
797b
|
23 lines
COMPUTERIZED VIDEOKERATOSCOPES DATA DISPLAY
Curvature Maps
The values used to draw the curvature maps
can be calculated based on the axial or the
instantaneous corneal radius.
The axial radius (also called the sagittal
radius) is the distance normal to a
peripheral corneal point to a single axis.
The instantaneous radius (also called
tangential, true or local radius) is a radius
of a peripheral point which is independent
of any axis of the cornea. With the cornea,
as it becomes more aspheric in the
periphery, the center of curvature moves
away from the central axis of the cornea
forming a locus of centers of curvatures.
The instantaneous radius is more accurate
and sensitive to changes in curvature. It is
longer than the axial radius.