Laser thermal keratoplasty, or LTK, is a type of eye surgery which was introduced in the 1990s to treat long-sightedness. The procedure involves using the heat from a laser to shrink a ring of tissue on the cornea, the eye's transparent covering. This creates a tight band around the eye which steepens the angle of the cornea and serves to make the eye more short-sighted, correcting the long-sightedness. As the effects of the procedure are only temporary, other more permanent techniques may be preferred over laser thermal keratoplasty. Most of these techniques also change the shape of the cornea and involve removing or lifting a small piece of corneal tissue which may be replaced later in the operation.
In order to be considered for a laser thermal keratoplasty, people must usually be over 40 years of age with vision that is considered stable. The cornea needs to be suitably shaped and free from scars. An extremely irregular or scarred cornea would more commonly be treated with another operation such as corneal transplantation or optic keratoplasty, where a corneal transplant is used to replace unhealthy corneal tissue. People who are pregnant or who have diabetes or a deficient immune system may not be accepted for laser surgery due to the risk of complications. Other problems such as cataracts or glaucoma may also mean this type of surgery is unsuitable.
During a laser thermal keratoplasty operation, the eye is numbed using anesthetic eye drops. The surgeon uses a special microscope called a slit-lamp to examine the eye before using the laser to shrink circles of corneal tissue around the outside of the pupil. Laser light is transmitted to the cornea in pulses, and the heat from each pulse shrinks a spot of corneal tissue, forming a depression. The laser moves in concentric circles, creating rings of depressions, effectively scoring the surface of the eye and altering the shape of the cornea.
Laser thermal keratoplasty is normally carried out with the aim of over-correcting the eye, making it short-sighted initially. It may be necessary to wear spectacles for some weeks following surgery, after which time the eye should have attained normal vision. As more time elapses, the vision typically deteriorates, with many patients becoming long-sighted again after a year or so.
The advantages of a laser thermal keratoplasty include that the procedure is quick, straightforward and usually pain-free. Negative aspects of laser thermal keratoplasty include the fact that vision may be blurred and the eye may feel scratched for a few days after the operation. There is a slight risk of infection, and antibiotic eye drops are usually taken to prevent this from occurring.