Automated lamellar keratoplasty (ALK), also known as keratomileusis in situ, is a non-laser lamellar refractive procedure used to correct high degree
refractive error
Refractive error, also known as refraction error, is a problem with focusing light accurately on the retina due to the shape of the eye and or cornea. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism ...
s.
This procedure can correct large amounts of myopia and hyperopia. However, the resultant change is not as predictable as with other procedures.
Procedure
ALK uses a device called a
microkeratome
A microkeratome is a precision surgical instrument with an oscillating blade designed for creating the corneal flap in LASIK or ALK surgery. The normal human cornea varies from around 500 to 600 micrometres in thickness; and in the LASIK procedur ...
to separate a thin layer of the cornea and create a flap.
The eye is
anesthetized
Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), am ...
and a ring is fixed to it in order to keep it properly positioned and flat. The microkeratome then makes a small incomplete flap across the cornea by cutting across it. While still attached at one side, the corneal flap is folded back to reveal a sub layer of cornea.
At this point, the microkeratome is precisely readjusted to match the calculated cut depth for the patient's vision correction. The calculation is based on the patient's glasses and contact lens prescriptions. The surgeon then passes the microkeratome completely over the eye making the power cut. After the power cut, the corneal flap is laid back over the eye where it reattaches.
ALK is a technique used to correct very high levels of myopia and is generally used from -5.00 to -18.00 diopters of nearsightedness.
Advantages and disadvantages
Healing time from ALK is very rapid, usually in about 24 hours or so. Results are immediately realized, though it may take several months for the vision correction to finally stabilize.
On the down side, the results of ALK are not as highly predictable as with the laser procedures of
LASIK
LASIK or Lasik (''laser-assisted in situ keratomileusis''), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and an actual cure for astigmatism, sinc ...
or
PRK.
Other disadvantages include irregular
astigmatism
Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at n ...
, long visual recovery time and tissue damage.
See also
*
LASIK
LASIK or Lasik (''laser-assisted in situ keratomileusis''), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and an actual cure for astigmatism, sinc ...
References
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Eye surgery