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.
The Casebeer System for Predictable Keratorefractive Surgery; One-year Evaluation of 205
Theodore P. Werblin, MD, PhD, G. Michael Stafford, BS
Ophthalmology, July 1993
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
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
- Reported side effects included glare, starbursting, and fluctuating vision.
Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study 10 Years After
George O. Waring III, MD, Michael J. Lynn, MS, Peter J. McDonnell, MD and the PERK Study
Archives of Ophthalmology, October 1994
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
- 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.
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
Peter J. McDonnell, MD, A. Nizam, MD, Michael J. Lynn, MS, George O. Waring III, MD, and
the PERK Study Group
Ophthalmology, February 1996
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.
A Consecutive Series (1982 - 1985) of Radial Keratotomies Performed with the Diamond Blade
M. Deitz, MD, D. Sanders, MD, M. Raanan, MD
American Journal of Ophthalmology, 1987
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
- A significant decrease in vision with glasses after surgery occurred in 0.3% of eyes.
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