Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

CHAPTER 5
5.3.4. Ablation patterns in cornea
We applied the depth conversion factor and the ablation efficiency factor from Eq. 5.3
to the ablation patterns measured on flat surfaces to predict the ablation pattern on
corneal tissue. Figure 5.6 shows predictions of the ablation profiles on flat and
spherical corneas (Fig. 5.6(b)), from the ablation profiles measured on flat plastic
surfaces (Fig. 5.6(a)). The differences in the ablation profiles as measured on
Filofocon A between the Alcon and Bausch and Lomb lasers are clear in Fig. 5.6(a).
In Filofocon, the Alcon laser (higher fluence) penetrates deeper in the plastic material
and has a narrower ablation area while the Bausch & Lomb pattern on plastic is wider
and shallower. The large differences in response between lasers are attenuated when
the corresponding conversions to corneal tissue are applied (Fig. 5.6(b)). However, the
ablation depth is significantly higher in cornea for the Bausch & Lomb laser, and the
laser efficiency effects not negligible for this laser.
a)
b)
Fig. 5.6. Ablation profiles measured in Filofocon A flat surfaces (a) and predictions in
corneal tissue (b) for flat and spherical surfaces.
We also estimated the ablated volume from the predicted 2-dimensional corneal
ablation patterns, for the Alcon and the Bausch & Lomb lasers, considering the
experimentally measured ablation efficiency factor. Table 5.2 shows the ablation
depth measured in Filofocon A, the nominal depth in cornea provided by the laser
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