Final answer:
The laser spot size may change as the laser penetrates deeper into tissue due to scattering and diffraction, potentially affecting precision and effectiveness of treatments like laser vision correction, where a UV laser is used to evaporate thin layers of corneal tissue accurately.
Step-by-step explanation:
The change in laser spot size from the surface to deeper tissue during procedures like laser vision correction is a concept rooted in the field of Physics, particularly in the understanding of laser-tissue interaction. When a laser is applied to the skin's surface, the spot size is the area over which the laser's energy is distributed. However, as the laser penetrates deeper into the tissue, depending on the laser's wavelength and the optical properties of the tissue, the spot size may increase due to scattering and diffraction. This phenomenon can affect the precision and effectiveness of the laser treatment.
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For example, during laser vision correction procedures, a computer-controlled laser applies brief bursts of 193 nm ultraviolet light, which are strongly absorbed by the corneal tissue, allowing for precise evaporation of very thin layers. A typical spot is less than 1 mm in diameter and about 0.3 µm in thickness. This controlled application helps in the correction of nearsightedness, farsightedness, and astigmatism, demonstrating the capability of fine manipulation of corneal tissue with high accuracy, leading to improved vision in the majority of patients.