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
- 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
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.