1. Isfahan University of Medical sciences
Pentacam Topography
Mohammad Ghoreishi, MD
Isfahan University of Medical sciences
Isfahan, Irann

2. Topography systems Placido disc (reflection) based Elevation based
PAR Corneal Topography System (PAR CTS)
Slit scanning
(Orbscan)
Scheimpflug imaging
(Pentacam, Galilei ,..)

3. Problems with placido systems
Assuming sphero-cylindrical optics on a smoothly reflective convex surface that falls within certain pre-determined parameters
Can not read if the cornea is badly distorted
Curvature is reference based
Elevations (shape) may not
always be accurate

4. Michael W. Belin, M.D., AAO Annual Meeting 2003, Anaheim, CA
Elevation Data
Elevation represents true shape of the cornea
It is independent of axis, orientation or positioning.
All subsequent maps (curvature …) can be derived from accurate elevation data
There is no reason for an elevation based topography system to incorporate Placido derived data unless their elevation data is unreliable
Michael W. Belin, M.D., AAO Annual Meeting 2003, Anaheim, CA

5. Elevation Based Systems
B & L OrbScan
Scanning Slit
Accuracy?
Relies on Placid augmentation
PAR CTS
Rasterphotogrammetry
Accurate but not commercially available
Oculus Pentacam
Rotating Scheimpflug images

6. ضمن عرض پوزش
بدلیل حجم بالای LECTUER ادامه اسلایدها امکان پذیر نمیباشد در صورت نیاز به ادامه لطفا به واحد سمعی و بصری مرکز آموزشی درمانی فیض مراجعه و یا با شماره تلفن داخلی 392 تماس حاصل نمائید
با تشکر