Correcting Refractive Errors of the Eye - Laser Thermal Keratoplasty

Laser Thermal Keratoplasty is a laser eye surgery that is meant to increase the curvature of the cornea and thereby correct farsightedness and astigmatism. It is a fairly new laser eye surgical procedure though its earliest pioneers began working with a version of the procedure over 100 years ago. It is among the most rapid and least invasive procedures for correcting refractive errors of the eye. In laser thermal keratoplasty or, LTK for short, a laser beam is focused on the cornea which heats, shrinks, and reshapes it. There is no real cutting or excision of tissue with laser thermal keratoplasty so it is not associated with many of the complications that can occur with LASIK, LASEK, and photorefractive keratectomy.

 

 

On the microscopic and molecular level, laser thermal keratoplasty heats the cornea to only about 140 degrees Fahrenheit, but that is enough to shrink collagen, an elastic protein found throughout the body and in the cornea. When the eye surgeon makes a ring around the pupil in the cornea, this shrinkage of collagen can change the shape of the front of the eyeball. Laser thermal keratoplasty uses a holmium:YAG laser to create just the right beam and heat the tissue to just the right temperature. 

 

Laser thermal keratoplasty is performed under local anesthesia, just like other laser eye surgeries. However, since laser thermal keratoplasty is a quicker procedure and does not require cutting with a blade or infusion of alcohol, the local anesthetic needs only to be applied for brief period of time.

 

Unfortunately, laser thermal keratoplasty is not always permanent and many people have regression toward their native vision within six months to two years after the procedure. Thus people will notice a correction of vision soon after the procedure but then the benefit begins to fade as time passes. The procedure is slightly more promising for people that have undergone an ablative laser eye procedure such as photorefractive keratectomy but experienced an overcorrection. In these cases, laser thermal keratoplasty has been shown to be able to reverse to overcorrection of the original procedure. This effect is somewhat longer lasting than when native vision is being corrected by laser thermal keratoplasty.

 

Some researchers have reported in the clinical literature that newer laser thermal keratoplasty technologies are yielding longer lasting results, i.e. correction of farsightedness for longer than two years. Unfortunately, long term studies showing a consistent benefit to laser thermal keratoplasty have yet to be published. It seems that in most patients there is some return of farsightedness in patients after laser thermal keratoplasty.

 

Laser thermal keratoplasty is a non-contact alternative to other laser vision correction surgeries such as LASIK (laser-assisted in situ keratomileusis) and LASEK (Laser Assisted Subepithelial Keratectomy) which require some cutting of the eye. In contrast to these procedures, laser thermal keratoplasty or LTK is very quick and has remarkably few complications. There are some drawbacks to the procedure, however. Only patients with farsightedness and astigmatism can be treated with laser thermal keratoplasty. Most importantly, what is sacrificed for a laser surgery without cutting is the permanent vision correction of other laser eye procedures.