Developed and heavily modified over the last 30 years. It works by making microscopic incisions at the edge of the cornea avoiding the line of sight and is much less invasive and drastic than LASIK. It is often described by the laser clinics as an old technique, superseded by LASIK. It is in fact currently the only procedure with a long term safety history (well over 30 years) with no significant long term complications. It is also safe from most problems associated with laser. This procedure can also be used to correct some of the effects of unsuccessful laser surgery. It is also very useful in the correction of astigmatism after cataract surgery. Pupil size and corneal thickness are very rarely a limiting factor (it can be a problem with excimer laser).
Most of the effect can be seen as soon as the pad is removed. No tissue is removed from the eye and it avoiding the line of sight help preserve night vision.

What is short sightedness ?
An eye which is myopic (short or near sighted) is usually longer or the front is steeper than normal. This causes the light rays to meet at a point in front of the retina. As a result, distant objects become blurred and only close objects can be seen clearly

Microsurgery
Diamond microsurgery or RK (radial keratotomy) was first used over 30 years ago and has been steadily improved since then. It works by making microscopic incisions at the edge of the cornea (but not to the very edge these days) which avoid the line of sight. It is much less invasive than LASIK and it has a safety history of over 30 years with no significant long term sight threatening complications.

Details
The cornea is flattened by applying 2-8 short incisions away from the line of sight. When these heal the cornea is very slightly flatter thereby correcting short sight. Microsurgery is able to treat low to medium levels of shortsightedness (myopia) up to –7 dioptres depending on age.
In contrast, laser eye surgery achieves the same flattening effect by removing a layer of tissue from the cornea usually after cutting a large 9mm flap with a metal cutter.

Laser eye surgery (LASIK, LASEK, PRK, Wavefront, etc.) is largely thought to be the only form of refractive surgery, due to the massive advertising coverage. In fact it is only one of the many options.
Myopia Surgery Center prefers RK,AK,CK as compare to Lasik for their patients because Lasik falls down on both of our principles: it operates over the visual zone and relies on burning off central parts of the cornea.
Some of our procedures are suitable for correcting problems caused by laser surgery. If you are concerned about side effects, LASIK depends on the surgeon cutting a very large corneal flap and using an excimer laser to burn off the tissue underneath. In the case of PRK, the surface is scraped off, in the case of LASIK a rotating blade, like a mechanical cutter, is used. The depth of this may vary by up to 40%. This flap never actually heals as corneal fibres do not re-grow and can be lifted even years later. These are the two underlying causes of problems associated with laser surgery. Renouned group of eye surgeons in London conducted trials of these procedures and decided to avoid them because of the uncertainty over long term safety.

Status of RK in UK
10,000 Operations And 11 years Later British Surgeon Remains Happy about RK by John F Henahan

NICE - After evaluating the outcome of 10,000 patients on who he has performed incisional refractive surgery over the last 11 years, William Jory, FRCS, FRCOphth tells the ESCRS Congress that radial keratotomy is safe, effective and preferable to PRK for correcting the same range of myopia.
Most of the patients had pre-operative refractive errors in the 2-7 dioptre range but in some cases they were as high as 8.0 D. About 25% also had astigmatism of between 1 and 5 D. At the latest follow up, only two eyes lost two or more lines of BCVA. Another 180 eyes, with irregular astigmatism, lost one line, but 5% gained a line, said Mr. Jory, in private practice in London, England. "Two of the eyes that lost two or more lines were associated with infection. One involved poor patient selection on my part. He was a 65 year old diabetic. The other infection occurred three years after the patient underwent RK and after she began to wear soft contact lenses against my instructions. It is well known that these lenses can transmit infections on to old scars," W Jory told Euro Times. He said that he makes no more than eight radial incisions and uses only four whenever he can. In his experience, four incisions achieved correction to within 1.0 D of the intended target in 98 out of 100 eyes. "The limiting optic zone is 3.0 mm. There is only so much correction you can achieve with four incisions, increasing with the age of the patient. Eight incisions can achieve another 20%, and doubling it only adds another 10% of correction" I treat all of my RK patients on a day care basis and I give them 10 mg of Valium® as a mild sedative before surgery. Once the patient is in the operating theatre, I apply an anaesthetic locally to the eye and most patients are happy with that. I had only one patient who told me after I had made the first incision that she would prefer to continue the operation under general anaesthesia, Mr. Jory said.

Double-Edged Blade Preferred.
To create the incisions, he prefers the American single pass technique, cutting towards the limbus with a double edged Duo-Trak ® diamond knife with a partial guard on the leading edge. For the typical 30 year old patient, he finds that the blade allows an additional dioptre of correction over a single blade. " In eyes with more than 1 D of astigmatism, I place equidistant transverse incisions across the steepest meridian at 6.0 mm from the optical centre. That flattens it, but the meridian at right angles steepens as well. The trick is to get the ’two meridians as equal as possible. With that procedure I can correct astigmatism up to 5.0 D," he points out.

Few Complications
"Aside from those two very rare cases of infection, there have been no other serious complications in my eleven year experience with RK. We have not had a single case of corneal rupture and I believe that it is a myth, as some critics of RK maintain, that these eyes are more susceptible to such ruptures than untreated eyes. "There were a few cases of persistent photophobia, but there is also evidence that RK will eliminate photophobia existing prior to surgery. You also have to watch out for a shift to hyperopia later on, but I find that I can reduce that possibility by being a little conservative. with my surgery and aim for correction to a half dioptre," Mr. Jory said, adding: "I find that to get the best results with RK, it is very important to do very careful ultrasound pachymetry and to be very conscientious about checking the accuracy of my diamond knife calibration every day. It is also important that the surgeon be ambidextrous during surgery, since if you can use only one hand, the procedure becomes a little awkward and there is the possibility that you will find a twist in your incision. "I believe that RK is so effective because it embodies good surgical principles and, unlike PRK, avoids surgery on the central visual cornea. It also has a very good and long track record. I used to do PRK but I am not as enthusiastic about it as I once was because it involves the visual axis and can result in a loss of contrast sensitivity and night vision in some eyes. Therefore, I carefully explain these things to my patients when they come to my office and find that it is very rare that they will decide to have PRK. "I do not do LASIK because of my concerns about the actual and potential complications that may be associated with that procedure both in the short and long term. It is difficult to imagine a more destabilising corneal procedure. If I have a patient with myopia higher than is treatable with RK, I usually refer them to a surgical colleague who has had great success following implantation of an IOL in those highly myopic eyes," Mr. Jory said.