The Excimer Laser

The word "Excimer" is a contraction of "excited" and "dimer". Dimer merely refers to the combination of atoms of argon and fluorine gases, to form an unstable molecule. When this unstable molecule breaks down, it emits photons of ultra-violet light, which are used in the laser. The excimer laser is a "cool" laser, which does not generate heat in the cornea. The laser photons destroy intermolecular bonds in the corneal tissue resulting in tissue removal by a process called photoablative decomposition. The absence of damage to the cells surrounding the ablated tissue renders this laser particularly suitable for delicate eye procedures. Removal of corneal tissue centrally flattens the corneal curvature. This alters the path of the light rays entering the eye, and allows precise retinal focusing in myopia. The laser is used to perform photorefractive keratectomy (PRK) for correction of myopia and phototherapeutic keratectomy (PTK) for removal of corneal scars. The Summit Excimer laser has been used to perform almost 50,000 PRK procedures till date, with extremely encouraging results.