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Vision
Correction Techniques
Radial
Keratotomy (RK)
Radial keratotomy (RK) was the first surgical procedure to be widely
used to correct nearsightedness. Radial keratotomy was invented in the
Soviet Union in 1973 and was first performed in the United States in
1978. Because of the availability of excimer laser, RK is seldom
performed today. We do not currently perform RK at the Caster Eye Center.
RK was used to correct nearsightedness by altering
the shape of the cornea. The doctor made a series of incisions in the
periphery of the cornea. This increased the corneal curvature slightly
where the incisions were made, and decreased the curvature in the central
portion of the cornea. The incisions were made in a radiating pattern,
like the spokes on a bicycle wheel. By varying the number, length, depth
and location of these incisions, different amounts of nearsightedness
can be corrected.
Effectiveness
of Radial Keratotomy
Radial keratotomy has been able to correct mild and moderate
nearsightedness, up to about 6 diopters.
However, because excimer laser treatment is more accurate, RK is
very rarely performed today.
Side
Effects
All RK patients experience some side effects. They are most
noticeable during the early healing phases, but in rare situations may
be permanent.
Daily fluctuation is a shift in the vision toward nearsightedness as the
day progresses. This occurs in all RK patients, but to a noticeable
degree in about 10%. If significant, the patient may need to wear
glasses for some nighttime activities, such as driving or watching a
movie.
The star-burst effect is a star-like pattern of reflections, most
noticeable when a bright light is viewed against a dark background. This
effect is prominent during the healing phase and diminishes over time.
Light sensitivity is also prominent during the early healing phases. It
usually quickly disappears, though rare patients can have persistent
difficulties.
Complications
of RK
The most common complication of RK is under-correction or
over-correction. Under-correction is treated by a repeat procedure,
known as a "touch-up" or "enhancement" procedure.
Over-correction, which results in farsightedness, usually must be
treated with glasses or contact lenses. Fortunately, serious medical
complications are very rare, but do occur. Serious complications include
infections, irregular healing, and improper placement of the incisions.
Progressive hyperopia is a development of farsightedness (hyperopia)
months or years after RK, and is more common in patients requiring large
corrections.
Excimer laser techniques (Lasik and PRK) do not experience this
problem at all.
ASTIGMATIC
KERATOTOMY (AK)
Astigmatic keratotomy (AK) is a variation of RK used to treat
astigmatism. AK involves arc-shaped incisions in the cornea, whereas RK
involves radial incisions (like the spokes of a wheel). AK is often
performed in conjunction with RK. The side effects from AK are mild and
healing is generally quick and easy. AK will diminish or eliminate
astigmatism. At the Caster Eye Center, we use the excimer laser to
correct astigmatism, so AK is used very rarely.
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