Oct 07 2011

RK Surgery Complications: How to Treat Hyperopic Shift and Anisometropia

Published by at 11:32 pm under RK Radial Keratotomy

For the past twenty years, many patients have come through our clinic who have had RK (Radial Keratotomy). Many have done well. Many have not done so well. This is more evident many years after the procedure. The purpose of the article is to highlight one specific problem that can occur after the surgery-changing vision.

Radial Keratotomy was discovered by Doctor Svyatoslav Fyodorov, a Russian eye surgeon. He removed glass from from one of his young patient’s eyes. After the boy’s eyes healed, his vision was considerably better.

Radial Keratotomy was very popular in the late 80s and early 90s. It was performed under a surgical microscope by a surgeon who made incisions with a diamond knife that was calibrated to make sure that it would not cut completely through the cornea. By making radial incisions, the clear part of the eye (cornea) was flattened. A flattened cornea removed the effects of nearsightedness (myopia). This method is rarely performed today because of the advances in LASIK technology.

RK incisions heal very slowly and join to neighboring tissue through fibrous tissue. The average number of incisions ranged from four to thirty-two.

Complications of RK incisions include poor night vision, susceptibility to infection, Distortion of the cornea, weakening of the eye, and constantly changing vision that shifts from nearsightedness (myopia) to farsightedness (hyperopia). All of these complications are due to the way the eye heals after surgery. Poor night vision results from night lights scattering at the radial cuts. This is made worse when the pupil becomes larger, as it does at night.
Infections are more common after surgery because of the incisions. Distortion, loss of strength of the eye, and shifting vision are a result of the way incisions heal and the ever changing state of regenerating tissue, atmospheric pressure, and dryness. A significant complaint is shifting vision. The once nearsighted patient who once achieved perfect vision realizes that they eye changes and with it the clear vision fades away.

The vision after RK, especially with patients who had a large amount of nearsightedness, changes over time. Sometimes both eyes change equally. Sometimes one eye changes more than the other. The result is a patient who needs farsighted distance correction and reading correction earlier than they would have needed it if they had not had the surgery. When two eyes have very different prescriptions, the resultant vision becomes unbearable. A thicker spectacle lens may magnify the image. If this happens one eye will see an object larger than the other eye. Eye strain, headaches, and discomfort may result.

The RK eye does not lend itself well to laser treatment such as LASIK because of the radial incision complicates surgery and healing

If surgery and spectacle correction are not called for, contact lenses may be fitted and a patient may have excellent results and nothing further will need to be done to correct the vision. Fitting a contact lens on an RK cornea can be a challenge. That is because the shape of the eye has been permanently changed making it difficult for the contact lens to center on the eye. Surgery may be needed.

There are options for surgical intervention. In some cases, cataract surgery is performed before a cataract is noticed. By doing this method of surgery, an implanted lens can replace the natural lens of the eye. Calculations are made by the surgeon and a prescription power implant is placed inside the eye. The new lens, allows better focus of the light. A small amount of LASIK surgery may be tolerated.
If the RK cornea has become distorted and diseased, it can be corrected using cornea transplant surgery. Most patients and surgeons alike turn to this procedure only when there are no options left. Cornea transplantation surgery is largely successful, but presents many challenges and many variables. It may not be needed at first, but it may always remain an option. It is far better to find a less invasive and more effect surgery whenever possible. With this frame of mind, there is one procedure that should be considered: Purse-string Sutures for Hyperopia Following Radial Keratotomy.

When the reader clicks on this link, they will find a study published in the Journal of Refractive Surgery. This article is technical, but with careful reading, the details of the procedure will become clearer.

The RK incisions relax the cornea causing it to flatten. Flattening makes the eye less nearsighted. When the eye is at the target shape, vision is clear. When the eye becomes flatter than the target shape it becomes more farsighted. This makes it difficult for the patient to see distance and near. This can be successfully corrected with the purse-string continuous corneal stroma suture.

The purse-string suture is created by the surgeon opening up the RK incisions to 75% of the orginal depth. With a needle, a suture is made in a circle around the eye. The suture is very thin (10-0) and placed at 50% of the depth of the clear part of the cornea (stroma). Two circular sutures are placed in the cornea and tightened. The tightening closes the incision wounds and steepens the cornea. The steepened cornea becomes less farsighted and vision is improved.

Healing may take months, but the end results is a cornea at the target shape. When this occurs, vision improves and the need for spectacles and contacts are diminished.

In the coming weeks, this sight will show photographs, corneal topography, and vision data of a post surgical follow up performed late September 2011©.

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