The excimer laser uses a high-voltage electrical charge to transiently combine atoms of excited argon and fluorine; when the molecule, or dimer, reverts to its separate atoms, a charged photon is emitted. The word excimer comes from “excited dimer.” Srinivasan, an IBM engineer, was studying the far-ultraviolet (UV; 193-nm) ArF excimer laser for photoetching of computer chips. He and Trokel, an ophthalmologist, not only showed that the excimer laser could remove corneal tissue precisely with minimal adjacent corneal damage—photoablation—but they also recognized its potential use for refractive and therapeutic corneal surgery.
Photoablation, the removal of corneal tissue with minimal adjacent corneal damage, occurs because the cornea has an extremely high absorption coefficient at 193 nm. A single 193-nm photon has sufficient energy to directly break carbon–carbon and carbon–nitrogen bonds that form the peptide backbone of the corneal collagen molecules. Excimer laser radiation ruptures the collagen polymer into small fragments, expelling a discrete volume and depth of corneal tissue from the surface with each pulse of the laser (Fig 5-1) without significantly damaging adjacent tissue.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.