Radial Keratotomy: The Early Refractive Surgery That Came Before LASIK
Before LASIK, PRK, and SMILE became available, radial keratotomy was one of the primary surgical procedures used to reduce nearsightedness.
Radial keratotomy, commonly called RK, does not use a laser. Instead, the surgeon makes a series of deep, spoke-like incisions in the cornea. These incisions weaken the peripheral cornea, allowing the center of the cornea to flatten.
Flattening the central cornea reduces its focusing power and can correct myopia. RK was an important step in the development of refractive surgery, but it has largely been replaced by procedures that provide greater precision and refractive stability.
Today, eye doctors are more likely to care for patients who had RK decades ago than to recommend RK as a new vision-correction procedure.
How Does Radial Keratotomy Work?
The cornea is the clear, dome-shaped tissue at the front of the eye. It provides much of the eye’s focusing power.
In a nearsighted eye, light focuses in front of the retina rather than directly on it. RK was designed to reduce the focusing power of the cornea by making it flatter.
During the procedure, the surgeon used a calibrated diamond blade to create several radial incisions extending from the peripheral cornea toward a clear central optical zone. The pattern resembled the spokes of a wheel.
The incisions did not normally cross the center of the cornea. As the wounds responded to pressure from inside the eye, the peripheral cornea became steeper and the central cornea flattened. The amount of correction depended on factors such as:
The number of incisions
The depth and length of the incisions
The diameter of the central optical zone
The patient’s age
The original prescription
The individual healing response
The standardized technique used in the major Prospective Evaluation of Radial Keratotomy, or PERK, study involved eight manually created radial incisions.
What Did RK Correct?
Radial keratotomy was primarily used to treat myopia, or nearsightedness.
Some patients also received additional transverse or arcuate incisions to reduce astigmatism. These combined procedures could produce more complicated changes in corneal shape.
Unlike LASIK and PRK, RK did not use a laser to remove microscopic amounts of tissue. Its effect depended on the placement of incisions and the biomechanical response of the cornea.
This made the result less predictable. Two patients with similar prescriptions could heal differently and experience different amounts of correction.
Was Radial Keratotomy Successful?
Many patients initially experienced a meaningful improvement in uncorrected distance vision.
At the 10-year point in the PERK study, 53% of treated eyes had 20/20 uncorrected vision and 85% had 20/40 uncorrected vision or better. However, RK did not completely eliminate nearsightedness in every patient, and some eyes continued changing many years after surgery.
The major limitation was not simply the vision immediately after surgery. It was the long-term stability of the cornea.
Why Is RK Rarely Performed Today?
Modern procedures such as LASIK, PRK, and SMILE reshape the cornea with much greater precision. Their treatment patterns can be customized using detailed measurements of the eye, and they do not depend on multiple deep radial incisions.
RK has largely been replaced because its long-term effects can include:
Progressive farsightedness
Fluctuating vision throughout the day
Irregular astigmatism
Glare and starbursts
Reduced nighttime visual quality
Corneal scarring
Structural weakening of the cornea
Difficulty obtaining accurate measurements before cataract surgery
These problems may develop or become more noticeable years or decades after the original procedure.
Progressive Hyperopic Shift After RK
One of the most recognized long-term effects of RK is a gradual shift toward hyperopia, or farsightedness.
The cornea may continue flattening long after the initial healing period. A patient who originally had clear distance vision after RK may eventually become farsighted and require glasses for both distance and near tasks.
Between six months and 10 years after RK, 43% of eyes in the PERK study shifted at least 1.00 diopter in the hyperopic direction. Researchers could not reliably predict which individual patients would continue changing.
This shift can combine with presbyopia, the normal age-related loss of near focusing. As a result, an RK patient may begin needing reading correction earlier or may experience increasing difficulty at both distance and near.
Why Can Vision Change During the Day?
Some patients with previous RK see differently in the morning than they do later in the day.
While the eyes are closed during sleep, changes in corneal hydration and pressure can temporarily alter the shape of the weakened cornea. Vision may be blurrier or more farsighted shortly after awakening and then change as the day progresses.
A PERK study evaluating morning and evening measurements found that some operated eyes developed measurable changes in refraction, corneal curvature, and visual acuity over the course of a single day.
Patients may describe:
Clearer vision in the morning but blurrier vision later
Blur in the morning that improves after several hours
A glasses prescription that never seems consistently correct
Different vision under different lighting conditions
Increasing glare while driving at night
When significant fluctuation is suspected, an eye doctor may repeat the refraction and corneal measurements at different times of day.
Irregular Astigmatism After RK
A healthy cornea has a relatively smooth, regular curvature. RK incisions can create an uneven or asymmetric surface.
This produces irregular astigmatism, which does not always correct fully with conventional glasses.
Symptoms may include:
Ghost images
Double or overlapping letters
Shadowing around objects
Glare
Halos
Starbursts
Reduced contrast
Distorted nighttime vision
Vision that remains blurry despite a new glasses prescription
Corneal topography or tomography can create a detailed map of the corneal surface and help identify central flattening, asymmetric curvature, irregular astigmatism, or progressive structural change.
Can Glasses Correct Vision After RK?
Glasses may work well when the remaining refractive error is relatively regular and stable.
They may be less successful when the prescription changes substantially throughout the day or when the cornea has significant irregular astigmatism.
Some patients require different corrections for:
Distance
Reading
Computer use
Driving at night
Different times of day
The goal is not always complete freedom from blur. It may be to find the most useful and comfortable correction for the patient’s primary daily activities.
Contact Lenses After RK
Rigid gas-permeable and scleral contact lenses can provide better vision than glasses when an irregular corneal surface is responsible for the blur.
A rigid lens creates a smooth optical surface in front of the irregular cornea. A scleral lens rests on the white portion of the eye and vaults over the cornea, holding a layer of fluid between the lens and the corneal surface.
Research has found that mini-scleral lenses can correct residual refractive error and irregular astigmatism in appropriately selected post-RK patients.
Fitting these lenses can be complex because the post-RK cornea is often very flat centrally and steeper in the surrounding areas. Specialized reverse-geometry or scleral designs may be required.
Can Additional Laser Surgery Correct RK Vision?
Additional refractive surgery must be considered carefully.
LASIK can be challenging after RK because creating a flap may cross or disturb the previous radial incisions. In selected patients with stable measurements and adequate corneal tissue, a surgeon may consider a customized surface procedure such as PRK rather than LASIK.
However, additional laser treatment cannot eliminate every source of visual fluctuation, and removing more corneal tissue may not be appropriate when the cornea is structurally unstable.
Modern management must be individualized. Options described for selected cases include:
Glasses
Rigid gas-permeable lenses
Scleral lenses
Customized surface laser treatment
Corneal suturing
Corneal cross-linking
Specialized intraocular lenses
Corneal transplantation in severe cases
The correct approach depends on the patient’s corneal shape, thickness, stability, scarring, prescription, cataract status, and visual goals. Evidence for some surgical approaches remains limited, so patients should avoid assuming that every post-RK cornea can be “repaired” with another procedure.
Cataract Surgery After Radial Keratotomy
Patients who underwent RK in the 1980s or 1990s are now commonly reaching the age when cataracts develop.
Cataract surgery can be performed successfully after RK, but the planning is more complicated.
Intraocular lens calculations
Calculating the correct intraocular lens power requires an accurate measurement of corneal focusing power. RK changes both the shape and the relationship between the front and back surfaces of the cornea, making standard keratometry less reliable.
Modern formulas designed for eyes with previous refractive surgery can improve accuracy, but the final prescription may still be less predictable than it is in an eye that has never had RK. Studies continue to compare formulas and measurement strategies for improving IOL calculations in post-RK eyes.
Fluctuating measurements
Because an RK cornea may change during the day, cataract measurements taken at one appointment may differ from measurements taken at another time.
The surgeon may obtain:
Multiple sets of corneal measurements
Corneal topography or tomography
Optical biometry
Previous glasses prescriptions
Historical RK records
Measurements at different times of day
Having the patient’s prescription and surgical information from before RK can be helpful, although many patients no longer have those records.
Cataract incisions
The cataract surgeon must plan the surgical incision carefully so it does not cross or open a previous RK incision. Existing RK wounds can also temporarily swell after cataract surgery, producing early farsightedness or fluctuating vision.
Vision may therefore require more time to stabilize following cataract surgery in a post-RK eye.
Premium lens considerations
Multifocal and trifocal lenses require a relatively regular optical system to provide their best performance. Significant corneal irregularity, glare, or higher-order aberrations may reduce the quality of vision produced by these lenses.
Some post-RK patients may be better served by a monofocal, toric, light-adjustable, or small-aperture strategy. Lens selection must be based on detailed testing rather than a desire to choose the most advanced or expensive implant.
Patients should understand that glasses or contact lenses may still be needed after cataract surgery.
Protecting an Eye With Previous RK
RK incisions permanently alter the structure of the cornea. A significant impact to the eye may cause an old incision to reopen.
Patients with previous RK should use protective eyewear during:
Contact sports
Racquet sports
Construction work
Yard work
Activities involving flying debris
Jobs with an increased risk of eye injury
Sudden pain, redness, tearing, light sensitivity, or decreased vision after an injury requires prompt evaluation.
When Should an RK Patient Have an Eye Examination?
An examination is recommended when an RK patient notices:
A changing glasses prescription
Increasing farsightedness
Fluctuating vision
New glare or halos
Difficulty driving at night
Ghosting or distorted images
Contact-lens intolerance
Decreasing vision from a cataract
Eye pain or redness
A recent eye injury
A comprehensive evaluation may include refraction, corneal topography or tomography, pachymetry, slit-lamp examination, eye-pressure measurement, macular OCT, and a dilated retinal examination.
Post-RK Eye Care in Tampa
Radial keratotomy helped many patients reduce their dependence on glasses before modern laser vision correction became available. However, the cornea can continue changing decades after the original surgery.
At OPT-ISM Eye Care in Tampa, we can evaluate post-RK prescription changes, corneal irregularity, fluctuating vision, dry eye, contact-lens options, and cataract development. Detailed measurements can also help prepare patients for a more informed cataract or corneal surgery consultation.
Having a history of RK does not mean that clear, functional vision is no longer possible. It does mean that measurements, expectations, and treatment decisions must be approached carefully and individually.
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