Radial keratotomy (RK) is a refractive surgical procedure that was developed in 1974 to treat nearsightedness. It involves the use of a diamond blade to cut incisions in the cornea. The number of incisions varies with the amount of nearsightedness.
RK was developed in an era where refractive surgery was in its infancy, so it became quite popular. Over the years, however, it has fallen out of favor due to its numerous inherent problems. It’s largely been replaced by more advanced surgical techniques, such as laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).
There are a number of complications that can result from RK surgery.
RK incisions are made by hand using a marker template. These incisions are therefore not symmetrical, and each incision affects the cornea differently. In the majority of RK cases, this causes irregular astigmatism; when severe, this can cause blurring of vision, ghosting, multiple images, poor night vision, and fluctuating vision. Although there are other causes of fluctuating vision (see below), the ability of the human brain’s optical centers to compensate for the problems caused by irregular astigmatism varies by time of day, energy level, and fatigue. This compounds the issue, as patients’ ability to compensate for irregular astigmatism varies, causing even more visual fluctuations.
Traditionally, RK incisions are made to a depth of 90% of the corneal thickness. If a cut is overshot, the cornea could be perforated or cut through completely. RK can also over-or under-correct refractive error, leaving a patient with blurry vision. Without the advanced laser guidance that surgeons benefit from in LASIK and PRK, there is certainly room for error.
Another issue is the insufficient size of the clear zone of vision or decentration of this area. This can cause halos, glare, and multiple images.
One of the most common and burdensome complications is fluctuating vision, where the vision is clear at one time of day and blurry at another. Radial keratotomy cuts through 90% of the corneal tissue, compromising its structural integrity. The cornea naturally changes shape depending on the time of day, but these variations are normally so subtle that they are imperceptible. During the night, the cornea swells and flattens in shape. After awakening, the cornea gradually loses water and steepens in shape. As the cornea changes shape, light is focused differently and therefore vision varies. This process is greatly accentuated after RK because of the compromised strength of the cornea. This means a patient may need one pair of glasses in the morning, another at midday, and yet another for the evening. Needless to say, this is impractical. Soft contact lenses cause this same issue. While gas-permeable contact lenses can sometimes provide greater visual stability, comfort may limit their use.
When radial keratotomy results in over-or under-correction of refractive error, a patient may still have to wear glasses to see clearly. For these patients, traditional LASIK may be an option. This procedure is used to correct the residual refractive error in order to eliminate the need for glasses. In LASIK, a flap of corneal tissue is made and pulled back. A laser is then applied to remove the necessary tissue. The flap is then replaced, making for a speedy recovery. The problem with this approach is that the irregularity of the cornea is not corrected, and the visual aberrations may not be fully corrected, as part of the correction comes from the irregular cornea. Therefore, the vision is improved but the patient still has problems with the light scatter and blurring caused by the irregular cornea.
While traditional LASIK can correct nearsightedness or farsightedness after RK, it cannot smooth out a bumpy, irregular, cornea. Sometimes, the incisions made in RK are numerous, imperfect, and/or decentered, causing an irregular cornea. This can cause patients to see multiple images, halos, and glare. The use of topography-guided ablation allows for customized treatment to smooth out the surface of the cornea. By decreasing or removing the irregularity, a significant part of the visual correction is also decreased so the patient sees better very rapidly. With topography-guided ablation, a second procedure may be necessary 4-6 months later to fine-tune the vision.
Dr. Motwani uses Wavelight Contoura, the most powerful corneal topographic system on the market. It’s approved by the Food & Drug Administration (FDA) for the treatment of corneal irregularity. In addition to remedying over-or under-correction from RK, this technology restores proper corneal shape for sharp vision. The advantage of this procedure is that since the corneal shape is fixed and much more uniform, the quality of the vision is often dramatically improved. Patients often say it is the best vision they have ever had. By treating the irregularity, multiple images, ghosting, many night vision issues, and usually a large part of the refractive correction are also eliminated. Anything that is leftover can be fine-tuned by a second planned enhancement.
Corneal crosslinking (CXL) is a procedure that improves corneal strength. Some surgeons have advocated for its use to strengthen the cornea in RK patients in an attempt to minimize visual fluctuations. Unfortunately, as the incisions cannot be eliminated and are the root cause of the corneal instability, CXL has not been found to be effective. Strengthening the tissue in between the incisions does not strengthen the overall cornea. There does not seem to be a role for CXL in RK repair at this time.
Even though RK surgery has largely fallen by the wayside, many patients are still suffering from its complications. Thankfully, they now have options.
Over- and under-correction can be improved with LASIK.
Even better, topography-guided ablation can correct this residual refractive error, as well as smooth out the surface of the cornea. This is particularly important when there are numerous incisions, a decentered zone of vision, or other issues with the surgical technique.
If laser reconstructive correction is not performed, the other choices are scleral or RGP lenses.
As you can see, Dr. Motwani has plenty of options to help post-RK patients. Make your appointment for a consultation today.
There are several options for correcting refractive error surgically. Laser-Assisted In Situ Keratomileusis (LASIK) and Photorefractive Keratectomy (PRK) are the…Read More
When one makes the decision to have Laser-Assisted In Situ Keratomileusis (LASIK), they look forward to having fantastic eyesight. They…Read More
A normal cornea is smooth and symmetrical in shape. It easily focuses light entering the eye through its even surface….Read More