Photorefractive Keratectomy, or PRK, is a type of laser eye surgery for people who suffer from nearsightedness
(myopia), farsightedness(hyperopia) or astigmatism. It is similar to LASIK in that it involves using an Excimer laser to
reshape the cornea to minimize or eliminate your dependence on eyeglasses or contact lenses.It is different in that unlike
LASIK the eye surgeon doesn't need to use a microkeratome to make a flap, but instead is able to apply the laser directly to the
surface of the cornea to achieve the desired vision correction effect. PRK is better suited for people with thin corneas or certain
other corneal abnormalities where using a microkeratome might not be the best choice. Also it may be preferred for those in the
United States military where PRK is the approved procedure for those in active combat and certain other positions. PRK has been
approved by the FDA for myopia since 1995 and for hyperopia since 1998 and enjoys an excellent safety profile. Since it does
not use a microkeratome, there is no risk of flap complications. In PRK to correct myopia, the steep cornea is made flatter by
removing tissue from the center of the cornea. To correct hyperopia, the flat cornea is made steeper by removing tissue from the
outer edges of the cornea. To correct astigmatism, the cornea is transformed into a more spherical shape.
Photorefractive Keratectomy PRK Process
Photorefractive Keratectomy involves, much like LASIK, the reshaping of the cornea. Unlike LASIK which involves
removing the inner tissue of the cornea, PRK applies laser energy to change the surface of the cornea. Before surgery you will
need to have a careful review of your health and eye history. Then you will need to have a refraction to measure your actual
prescription. This will need to be performed with eye drops; in order to get the best measurements. The shape of the surface
of your eyes will be mapped using an instrument called a corneal topographer. Finally the thickness of your cornea will be
measured using an instrument called a pachymeter.
On your day of surgery, a technician will clean the area around your eyes with a hygienic but gentle cleansing pad. The
technician will place a series of drops into your eyes in order to get them ready for your treatment. Some of these drops,
antibiotic drops, will prevent germs from entering your eye and therefore help to prevent any possibility of infection. Other
drops will be placed in your eyes to lightly numb the cornea so that you are comfortable during your treatment. After you recline
on the bed-like chair under the laser, an eyelid holder called a speculum, is gently placed between your eyelids to remind
you not to blink. Next the epithelium, a thin, protective layer that covers the cornea, is removed. Since you have had numbing
drops placed in your eyes, this will not be uncomfortable, but will feel like a slight pressure around your eyes. The
surgeon will instruct you to look at a small light during your procedure. Don't worry if you cannot stay perfectly steady-just do
your best. Today's laser technology uses a tracking system which will actually follow your eye movements if you can hold
pretty still during your procedure. To correct nearsightedness, farsightedness or astigmatism, your surgeon will use an
Excimer laser. The Excimer laser is programmed based on calculations made from the measurements taken during your
consultation. The laser then delivers the exact correction needed and send tiny spots of light beams to certain
predetermined positions on your cornea in order to change the shape to what is required for you to see well. The eye surgeon
has full control of the laser and monitors the position of the laser on the cornea as well as the tracking system monitoring
the position of your eye in order to make sure the beam is in the correct place. The application of the laser usually takes
1-2 minutes per eye depending on the amount and complexity of the of correction that you need. A soft bandage contact lens may
be placed over the eyes to help the epithelium heal. The technician will often place additional eye drops in your eyes as the
procedure is finished just to give you some added comfort and protection and to help your eyes heal quickly. Most often a
protective clear plastic shield will be applied-like safety glasses-to prevent you from rubbing your eyes or in case you get
bumped accidentally. Pay careful attention to the detailed instructions your doctor gives you regarding additional drops to use at
home and when to return for your first visit.
You will need someone to drive you home. To be most comfortable, you should go home and take a long nap. When you awaken you
will notice several things. First you will notice a dramatic improvement in your vision. It will most likely not be as good as it
will get in a few days as your eyes will need to continue to heal. You should expect to feel some mild "grittiness" or like a
little sand or dust has gotten into your eyes for up to a day or so. This is normal. As your eyes heal it is normal and expected
to be a little sensitive to light and perhaps see some glare or even haloes around lights at night. This too will diminish as your
eyes heal.
Photorefractive Keratectomy Candidates
People are best suited for Photorefractive Keratectomy are people with moderate levels of myopia or hyperopia who
have corneal abnormalities that make them not best suited for LASIK. However PRK may also be used for people with high
prescription levels and for active military personnel.
Photorefractive Keratectomy Advantages
Better for thin corneas
Good for low to high levels of myopia or hyperopia
Better for thin corneas
Good for low to high levels of myopia,hyperopia and/or astigmatism
Good for people in military service
Photorefractive Keratectomy Disadvantages
Longer healing time
Longer time for results
Photorefractive Keratectomy Conclusion
Photorefractive Keratectomy is a less used procedure due to LASIK. However, it is still the procedure used when LASIK is not
the best choice due to eye irregularities. As with all laser surgery, there is always a risk and side effects like light
sensitivity and halos may not go away. It is important to talk with your eye care doctor about the risks in your specific case.
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