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Human corneal ablation threshold using the 193-nm ArF excimer laser
M W Berns1, L Chao, A W Giebel
1Beckman Laser Institute, University of California-Irvine, 92612, USA.
Investigative Ophthalmology & Visual Science
|April 2, 1999
Summary
The 193-nm ArF excimer laser shows varying ablation thresholds for human corneal tissues. Collagen in the stroma ablates at 30 mJ/cm², while keratocytes ablate at 40 mJ/cm², impacting corneal surface morphology.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Laser Surgery
Background:
- The 193-nm ArF excimer laser is widely used in ophthalmic surgery, particularly for refractive procedures.
- Understanding the precise energy thresholds for ablating different corneal layers is crucial for optimizing surgical outcomes and minimizing tissue damage.
Purpose of the Study:
- To determine the specific energy density thresholds required to ablate various human corneal structural elements using a 193-nm ArF excimer laser.
- To investigate how these varying thresholds influence the resulting corneal surface topography under simulated clinical conditions.
Main Methods:
- Human eye bank eyes were subjected to ablation using the VISX Star 193-nm argon fluoride excimer laser.
- Corneal tissues were exposed to a range of energy densities, from 10 mJ/cm² up to 160 mJ/cm².
- Post-ablation, corneas were prepared for light and transmission electron microscopy to analyze structural changes.
Main Results:
- Distinct ablation thresholds were identified for different corneal components.
- The ablation threshold for corneal stromal collagen was found to be 30 mJ/cm².
- Keratocytes exhibited a higher ablation threshold of 40 mJ/cm², leading to their presence on elevated stromal peaks post-ablation.
Conclusions:
- Corneal structural elements, including stromal collagen and keratocytes, possess unique and differential ablation threshold energy densities.
- These variations in ablation thresholds directly contribute to the formation of topographical irregularities on the corneal surface during laser ablation.