home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Contact Lens Series
/
Contact Lens Series Volume 1.iso
/
mac
/
Contact Lens Series V1(MAC)
/
Topogb.DIr
/
00046_Field_46.txt
< prev
next >
Wrap
Text File
|
1997-10-29
|
790b
|
22 lines
BASIC CONCEPTS
In order to obtain quantitative data that
would be more clinically useful,
photokeratoscopes were developed.
These instruments have a modified
PlacidoΓÇÖs disc, usually with an ellipsoidal
shape, which were reflected from the
cornea. The image of the pattern was then
photographed, usually with a Polaroid
camera. The picture was analyzed by
measuring the separation of the rings with
a projection system (comparator). By
knowing the separation of the rings and
proper calibration the corneal curvature
could be calculated. This procedure was
fairly long and tedious. With some of the
instruments this was done in the
practitionerΓÇÖs office while with others the
photos were sent to a laboratory for
analysis.