1 Introduction
2 Materials and Methods
2.1 Geometrical Reconstruction of the Human Cornea
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“Patch” surface generation function. Uses a NURB surface to reconstruct both corneal surfaces, minimizing the nominal distance between the 3D point cloud and the solution surface. A cubic NURB surface was used with a segmentation of 256 in each parametric direction. The surface so obtained, approximates the point cloud.
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“Mesh” model to generate a grid. In this case, the points lie on each surface, and then surfaces are obtained by interpolation. A rectangular grid of 21 rows and 256 columns was selected, being then deformed to minimise the nominal distance between the spatial points and the grid surface.
2.2 Practical Application
2.3 Statistical Analysis
Parameter (unit) | Difference | Healthy (n = 89) | Grade I (n = 24) | Grade II + III + IV (n = 18) | ||||
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Abs | %. | Stu. | Wilc. | Stu. | Wilc. | Stu. | Wilc. | |
Total volume (mm3) | 0.04 | 0.16 | 0.049 | 0.043 | 0.233 | 0.383 | 0.873 | 1.000 |
Ant. Apex area (mm2) | 0.05 | 0.08 | <0.001 | <0.001 | 0.025 | 0.041 | 0.178 | 0.183 |
Post. Apex area (mm2) | 0.02 | 0.03 | <0.001 | <0.001 | 0.026 | 0.003 | 0.152 | 0.197 |
Total area (mm2) | 0.04 | 0.03 | 0.015 | 0.061 | 0.443 | 0.603 | 0.553 | 0.875 |
Sag. plane apex area (mm2) | 0.04 | 0.93 | 0.373 | 0.419 | 0.875 | 0.692 | 0.029 | 0.018 |
Sag. plane area at MTP (mm2) | 0.02 | 0.39 | 0.033 | 0.161 | 0.655 | 0.534 | 0.862 | 0.409 |
Ant. apex dev. (mm) | 0.03 | 482.7 | 0.008 | 0.011 | 0.086 | 0.005 | 0.001 | 0.001 |
Post. apex dev. (mm) | 0.10 | 92.37 | 0.786 | < 0.001 | 0.063 | 0.064 | 0.464 | 0.084 |
Centre of mass X (mm) | 0.00 | 8.69 | 0.006 | 0.009 | 0.417 | 0.405 | 0.773 | 0.671 |
Centre of mass Y (mm) | 0.00 | 12.37 | 0.013 | 0.005 | 0.271 | 0.3 | 0.11 | 0.127 |
Centre of mass Z (mm) | 0.00 | 7.47 | 0.841 | 0.85 | 0.05 | 0.052 | 0.856 | 0.829 |
Ant. MTP deviation (mm) | 0.16 | 16.62 | 0.077 | 0.045 | 0.729 | 0.966 | 0.184 | 0.245 |
Post. MTP deviation (mm) | 0.16 | 17.81 | 0.125 | 0.014 | 0.796 | 0.853 | 0.374 | 0.889 |
3 Results
Healthy | Keratoconus | Total | |
---|---|---|---|
Total raw data | 100 | 61 | 161 |
Total modelled | |||
Grid | 89 (89%) | 42 (69%) | 131 (81%) |
Patch | 96 (96%) | 56 (92%) | 152 (94%) |