Radial Keratotomy (RK)
Photorefractive Keratectomy (PRK)

NOTICE: As of March 1995, Excimer laser PRK treatment for myoptic vision correction had not received final FDA approval. This laser is classified as an investigational device.

The purpose of this laser series is to educate the General Public on one of today's most promising Ophthalmic laser procedure.

The information and images on these web pages were first presented in 1985. The first functional Excimer laser system was exhibited during the American Academy of Ophthalmology Conference in Dallas, Texas in 1987.

This material originates from the early research performed by numerous physicians and physicists in the U.S. and Europe. At the time, the RK (Radial Keratotomy) had already been proven a viable treatment for mioptic vision correction.

This first image is a histological photo of a corneal specimen that had been  irradiated with an Excimer laser emitting at a wavelength of 193nm. This specimen,  as viewed through an electron microscope, reveals a very well defined incision  with a striking absence of any thermal damage. This process is known as Laser Photoablation. By controlling the pulse rate and exposure time, the depth of penetration  can be predicted very precisely. It was calculated that 1 joule/cm² ablates  corneal tissue to a depth of 1 µm. {1}

Just two months after the initial laser irradiation, this histological image  reveals a fillet or "plug" of Epithelium cells that has filled in the cavity that was created by the photoablation  interaction. Due to the cornea's amazing regenerative properties, new stroma  can be appreciated just below the Epithelium "plug". This is a  remarkable manifestation of the cornea's "wound healing" ability.  [This specimen was stained with uranyl acetate and lead citrate prior to  examination by a transmission electron microscope]

This Excimer laser induced Radial Keratotomy was a performed on a  human eye. The laser energy was delivered to the cornea through an eight  incision corneal mask held in place by a slight suction. There are number  of such mask for RK, Astigmatism, Penetrating Keratoplasty, etc. The slits are  clearly seen using the "red reflect" effect (photographer's red eye  effect) for contrast. An Ophthalmic Operating Microscope (Zeiss OPMI-1) with a  35mm camera attachment was used to capture this event. [The top of the head is  at the six o'clock position]

This is the same eye just one week post-op. As you can see, the incisions are  barely noticeable and the aesthetic appearance is very favorable. The arrows  point to the original incision sites. This laser RK produced a change of about  +2 diopters with an initial penetration depth of 300 microns (about 60% into  the central corneal thickness). The total central corneal thickness of the  typical human eye is about 600 microns. [The bright spot at the two  o'clock position is a reflection off the microscope's halogen illumination source]

Specific information on the actual procedure can be viewed at:

The American Academy of Ophthalmology

TLC The Laser Center

Footnotes:

1. Trokel SL, Srinivasan R, Baren B. Excimer laser surgery of the cornea. American  Journal of Ophthalmology 1983; 96:710-5.