OCULUS Pentacam Interpretation Guide

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3.6 Total Cornea Refractive Power map
This map (Figure 7) uses ray tracing to calculate the refractive power of the cornea. It takes into
account how parallel light beams are refracted according to the relevant refractive indices (1.376
and 1.336), the exact location of refraction and the slope of the surfaces. The location of refraction
is a determinant of surface slope, since the anterior and posterior surfaces have slightly differing
principal planes due to corneal thickness. In this way the map takes effects "A", "B", "C" and
"D" into account. Its results are more realistic than any other, but they will deviate from normal
(sagittal) SimK values so they cannot be used in conventional IOL formulas.
Figure 6: Calculation of power according to Snell´s law taking the different refractive
indices and the different principal planes of the anterior and posterior corneal
surfaces into account
Figure 7: Total Corneal Refractive Power map calculated by two spheric surfaces
of anterior r = 8 mm and posterior r = 6.58 mm and pachimetry
3 Differences between the various topography maps of Pentacam
®

OCULUS Pentacam Specifications

General

Measurement Time	Less than 2 seconds
Corneal Coverage	Up to 12 mm
Software	Pentacam Software
Data Transfer	USB
Corneal Topography	Yes
Display	External monitor required
Measurement Principle	Scheimpflug imaging
Camera	Rotating Scheimpflug camera
Light Source	Blue LED
Pachymetry	Yes
Anterior Chamber Analysis	Yes
Imaging Principle	Scheimpflug imaging
Fixation	Internal
Power Supply	100-240 V, 50/60 Hz
Resolution	High resolution
Lens Density Measurement	Yes
Dimensions	Varies depending on model and configuration
Weight	Varies by model, check manufacturer specifications
Number of Images	25 or 50