Figure 1 | |
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A meridional plane, depicted as an orange plane. This plane contains the corneal point of interest (shown as a green dot) and the videokeratograph axis (depicted as a red vector). | |
Figure 2 | |
The yellow cross-sectional plane contains the normal vector at the point of interest (shown as a green dot). This diagram differs from the one published in that this one has a green vector through the point of interest to indicate the surface normal at that point. | |
Figure 3 | |
Ths planes corresponding to the minimum and maximum curvature directions are shown in blue and red, respectively. This diagram differs from the one published in that this one has a green vector through the point of interest to indicate the surface normal at that point. | |
Figure 4 | |
This graph illustrates the base corneal model without keratoconus. The model is a simple sphere with constant axial power across its surface. This is represented here as a yellow straight line when plotting axial power vs. diatance. The power is denoted P_{sphere}, and is labeled in red. | |
Figure 5 | |
To model keratoconus, a section of the sphere is removed and replaced with a surface of revolution formed from a hyperbola. The axial power associated with the hyperbola between -t and t is shown as the yellow curve. The maximum power of the cone is denoted P_{cone}. | |
Figure 6(i) | |
This shows a mock-up, depicting in each figure component 6(i) thorugh 6(v), the center of the simulated cone (middle), instantaneous power (upper left), axial power (upper right), Gaussian power with a cylinder overlay (lower left), and the height map, or radial difference from the reference sphere (lower right). The center of the cone is at phi = 12° and theta = 215°. Here P_{cone} = P_{sphere} = 45 D; thus, there is no keratoconus and all power maps are constant. | |
Figure 6(ii) | |
Same as Fig. 6(i), except P_{cone} is set to 57 D of axial power, slightly larger than P_{sphere}. The cone is shown in green in the model. | |
Figure 6(iii) | |
The parameter P_{cone} has now reached its maximum value of 82 D. | |
Figure 6(iv) | |
The parameter P_{cone} is fixed at 82 D and the cone is rotated toward the center of the cornea. Its center is now at phi = 6°. | |
Figure 6(v) | |
The center of the cone is now at phi = 0° (directly at the north pole). | |
Figure 7 | |
The four views of regular fixation (patient looking directly into the center of the videokeratograph): instantaneous power (upper left), axial power (upper right), Gaussian power with a cylinder overlay (lower left), and the radial difference from a reference sphere (lower right). | |
Figure 8 | |
The four views of conic alignment (patient shifting his gaze direction up toward his left so that the cone alights with the center of the videokeratograph): instantaneous power (upper left), axial power (upper right), Gaussian power with a cylinder overlay (lower left), and the radial difference from a reference sphere (lower right). |