Excimer laser

The Excimer laser is the instrument used today in the majority of refractive surgical procedures.

Excimer laser surgery involves changing the shape of the surface of the cornea (the clear portion of the eye in front of the pupil) by ablationg thin layers off the fornt surface, and is not to be confused with radial-keratotomy which involves cutting into the cornea with a scalpel to alter its shape. The shaving is computer controlled and can be used to get rid of many refractive errors in a single treatment.

The two commonly performed surgical procedures utilizing the Excimer laser are photorefractive keratectomy (PRK) and laser assisted in-situ keratomileusis (LASIK). Recently Epi-Lasik has become another option.

The effect of excimer laser on the cornea is very similar to grinding of a glass lens to change its refractive power. In eyes with refractive errors, excimer laser because of its high level of precision, can change the shape of the cornea to change its refractive power to the desired state and thus correcting the refractive error.

• In myopia, the central part of the cornea is made flatter, and thus decreasing the refractive power of the cornea and of the eye, and thus correcting the refractive error.
• Similarly in hypermetropia, the laser removes a ring of tissue from the peripheral part of the cornea and thus makes the central part steeper and corrects the refractive error.
• As we know, in astigmatism, the cornea is more curved in one direction. Excimer laser can correct astigmatism also by selectively ablating the cornea in the required direction.

Treatment with the laser is quick and painless. The laser itself is a cold (non-heat generating) laser, which allows precise removal of tissue (for reshaping the corneal surface) without thermal damaging effects to adjacent tissue. The Excimer laser is an extraordinarily precise laser, which sculpts the surface of the cornea using invisible, high-energy wavelengths of light. The central cornea may thus be made either steeper or flatter depending on pre-existing refractive error. One may think of the Excimer laser as an instrument capable of reshaping the cornea in a fashion similar to that of placing a contact lens permanently on the cornea.