Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

OPTIMIZED LASER PLATFORMS
5.3.2. Ablation patterns on plastic
Figure 5.3 shows pairs (top row for flat surfaces, and bottom row for spherical
surfaces) of representative ablation patterns for all lasers of the study. In all cases, a
correction of –9 D was programmed in the laser. The ablation patterns differed notably
across lasers. While the Alcon and the Bausch & Lomb lasers provided highly
symmetric patterns on both flat and spherical surfaces, the pattern delivered by the
Wavelight laser showed asymmetries which were highly consistent across
measurements.
Fig. 5.3. a) Examples of ablation patterns obtained from ablated flat and spherical
surfaces for the three different lasers, and a correction of -9 diopters. b) Horizontal
sections of the ablation patterns on the flat surfaces (red lines), and other patterns
obtained from different flat samples ablated on identical conditions (blue lines).
Efficiency effects were responsible for a lower ablation depth in peripheral areas on
spherical than on flat surfaces. This effect is notably larger in low fluence lasers (i.e.
Bausch & Lomb laser) than higher fluence lasers (i.e. Alcon).
Figure 5.3 (b) shows horizontal profiles of the ablation patterns on flat surfaces.
The red lines correspond to the examples shown 2-dimensionally, while the blue lines
correspond to different repetitions corresponding to different samples. The high
similarity of the laser profiles estimated from different ablated samples (with the same
laser and similar conditions) illustrates the high repeatability, particularly of the Alcon
and Bausch & Lomb lasers. When asymmetries were present, as found with the
Wavelight laser, the differences across repeated measurements also increased. The
145