LASER THERMOKERATOPLASTY (LTK)
Laser Thermokeratoplasty is a non-contact laser refractive procedure on the cornea.
The procedure employs a holmium* laser to place a ring of concentric laser spots on the cornea either at the 6 mm of 7 mm optical zone. These spots cause a ring of constriction in the collagen fibres in the periphery of the cornea, leading to a central steepening of the cornea.
The steeper cornea enables the eye to focus better for close-up vision. Unfortunately it is often the experience that the effect may regress significantly over time. It is in principle similar to the conductive keratoplasty (CK) procedure, where a micro-needle high-radio frequency probe is used to create a ring of corneal spots in a similar fashion.
* For the technically-minded: Holmium is a chemical element with the symbol Ho and atomic number 67. It is a rare earth element, first discovered in 1878 by a Swedish chemist Per Theodor Cleve. He named the element after the city of Stockholm.
Elemental holmium is a relatively soft and malleable silvery-white metal. It is too reactive to be found in its natural form. It is used in yttrium-iron-garnet (YIG) and yttrium-lanthanum-fluoride (YLF) solid-state lasers. Holmium lasers emit electromagnetic radiation at a wavelength of 2.08 microns, which is safe for eyes.
Holmium lasers are used in a variety of medical, dental and fiber-optic equipment.
CONDUCTIVE KERATOPLASTY (CK)
In contrast to LTK, Conductive Keratoplasty is a contact refractive procedure on the cornea.
Here, a micro-needle probe, using a high-frequency radio wave, is used to create a ring of corneal spots on the cornea, leading to contraction of the collagen fibres within the cornea. The peripheral contraction of these fibres leads to central steepening of the cornea, which enables the eye to focus near or treats far-sightedness.