Radial Keratotomy (RK) Technical Info: The Vision Correction Website

Radial Keratotomy

History
The first records regarding incisions in the cornea to improve vision date to the 19th century. In the early 1970's, modern day radial keratotomy was given birth by a group of Russian ophthalmologists. These eye doctors used radial incisions in the cornea to decrease near-sightedness. They developed formulas that tried to improve the results and take into account the degree of near-sightedness that was present before surgery. The first radial keratotomy surgeries were performed in the United States in 1978 and were based on the Russian techniques.

Since its introduction, radial keratotomy has continued to be refined. The major goal has been to improve the predictability of the procedure and limit complications. Significant improvements have included the development of extremely sharp and precise diamond blades to make the incisions and highly accurate instruments to measure the depth of the blade and the thickness of the cornea.

Many scientific studies have been performed to assess the safety, stability and predictability of radial keratotomy. The following section includes a summary of the results from a few of the major studies.

Scientific Results

Title
The Casebeer System for Predictable Keratorefractive Surgery; One-year Evaluation of 205 Consecutive Eyes

Authors
Theodore P. Werblin, MD, PhD, G. Michael Stafford, BS

Publication
Ophthalmology, July 1993

Results
This study reports the results of surgery using a systematized approach to radial keratotomy that has gained more widespread use in the 1990's. Surgery was performed on 205 eyes between 1990 - 1991. Surgery was used to correct both near-sightedness and astigmatism in 85 eyes. Follow-up information was reported on 203 eyes 1 year after surgery.

These results showed:

99% of eyes achieved uncorrected vision of 20/40 or better.
86% of eyes achieved uncorrected vision of 20/25 or better.
45% of eyes achieved uncorrected vision of 20/20 or better.
33% of eyes required enhancement procedures (multiple surgeries)
A small, but statistically significant change after surgery in a far-sighted direction was noted.
Reported side effects included glare, starbursting, and fluctuating vision.

Title
Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study 10 Years After Surgery

Authors
George O. Waring III, MD, Michael J. Lynn, MS, Peter J. McDonnell, MD and the PERK Study Group

Publication
Archives of Ophthalmology, October 1994

Results
This study was the first major study of radial keratotomy in the United States and was funded by the National Eye Institute. Surgery was performed on 793 eyes between 1982 - 1983 to reduce near-sightedness ranging from -2.00 to -8.75 diopters. Follow-up information was available from 693 eyes 10 years after surgery.

These results showed:

70% of patients do not require glasses or contact lenses for distance vision after surgery.
85% of patients achieved uncorrected vision of 20/40 or better.
53% of patients achieved uncorrected vision of 20/20 or better.
43% of eyes continued to change after surgery in a far-sighted direction between 6 months and 10 years. The average change was approximately 1.00 diopters.
A significant decrease in vision with glasses after surgery occurred in 3% of eyes.

Title
Morning-to-evening Change in Refraction, Corneal Curvature, and Visual Acuity 11 Years After Radial Keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) Study

Authors
Peter J. McDonnell, MD, A. Nizam, MD, Michael J. Lynn, MS, George O. Waring III, MD, and the PERK Study Group

Publication
Ophthalmology, February 1996

Results
Seventy-one (71) patients who took part in the Prospective Evaluation of Radial Keratotomy (PERK) Study were evaluated an average of 11 years after surgery to determine whether their vision fluctuated from the morning to the evening. The study concluded that morning-to-evening change of refraction (eyeglass prescription) and vision persisted for at least 11 years in some patients after radial keratotomy, although in most patients the magnitude of this change is small. Thus, diurnal fluctuation may be a permanent component of radial keratotomy in some patients.

Title
A Consecutive Series (1982 - 1985) of Radial Keratotomies Performed with the Diamond Blade

Authors
M. Deitz, MD, D. Sanders, MD, M. Raanan, MD

Publication
American Journal of Ophthalmology, 1987

Results
Surgery was performed on 972 consecutive eyes between 1982 - 1985. Follow-up information was available from 671 eyes 1 year after surgery.

These results showed:

88% of patients achieved uncorrected vision of 20/40 or better.
31% of eyes continued to change after surgery in a far-sighted direction between 1 and 4 years.
A significant decrease in vision with glasses after surgery occurred in 0.3% of eyes.