Corneal Thickness Spatial Profile By Prof. Renato Ambrósio Jr - OCULUS Pentacam Interpretation Manual

11 Corneal Thickness
11 Corneal Thickness Spatial Profile
by Prof. Renato Ambrósio Jr
The measurement of corneal thickness has become an important factor in a variety of clinical
situations, including planning and evaluation of results of most types of corneal and anterior
segment surgeries and evaluation of corneal endothelium dehydrating function as well as its
consideration as a risk factor for glaucoma.
Ultrasonic central corneal thickness is usually referred to the measurements at the corneal geometric
center or at the apex, which is not the corneal thinnest point (TP).
Regional US pachymetry can been used, but the need for the pachymetric map for determining the
location and value of the cornea's TP becomes clear when we consider that the difference between
central and TP thickness is greater than 10 μm in over 10% of normal corneas.
Corneal tomography provides a three-dimensional reconstruction of the cornea, thus permitting
evaluation of the anterior and posterior corneal surfaces and thereby the creation of a pachymetric
map.
We believe tomography to be a better term for such diagnostic approaches. It derives from the Greek
word "tomos", which means "slice", and "graphia", which means "describing".
The aim of this section is to provide a comprehensive understanding of the current corneal thickness
profile studies that have appeared since the introduction of the Pentacam® software, along with
other approaches that could be developed in the future.
Corneal Thickness Spatial Profile (CTSP)
Corneal thickness values at the TP is determined and the averages of thickness values of the points
within twenty-two imaginary circles centered on the TP with increased diameters at 0.4 mm steps
are calculated to create the CTSP
Figure 75: The Corneal Thickness Spatial Profile (CTSP)
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(Figure 75).