Photorefractive keratectomy or PRK is a form of laser eye surgery that is also used to correct one’s vision. It was developed earlier than other methods of refractive procedures but despite that, both patients and eye specialists still consider PRK as an important form of eye treatment. Laser eye clinics also recommend PRK as an alternative to LASIK.
PRK corrects the eyesight by reshaping the cornea or the front surface of the eye so that the light that passes through the eye is redirected to the back or the retina. The formerly misguided rays, instead of passing through the cornea, will now be diverted to the retina. There are screening tests performed to the patient to determine whether he or she is fit to undergo PRK. This will ensure the safety of the patient and success of the process.
For example, mapping the cornea is an important part of the pre-operative procedures. Examining the corneal thickness of the eye is needed to evaluate the contours and shape of both the front and back surface of the cornea. This process will determine the presence or absence of any surface irregularities that could cause the failure of the PRK treatment. One way to measure corneal thickness is by means of a pachymeter. The corneal thickness still needs to be evaluated even if PRK will only treat the external layers of the cornea.
Some of the factors that help decide whether a patient is suitable or not for photorefractive keratectomy are the following criteria:
A minimum age of 18 years
Shortsightedness or myopia with a prescription of less than -12.00
Stable vision or prescription for at least a year in which the refraction is verified by an optometrist
Absence of medications that could potentially slow down the recovery process such as steroids and immunosuppresants
Absence of eye diseases such as macular degeneration or cataract
During the PRK process, a local anesthetic will first be placed over the eye to ensure a pain-free procedure. Following this, an excimer laser will remove the corneal epithelium which is located on the outermost layer of the eye. An alternative to an excimer laser would be a fine surgical brush that contains thinned out alcohol.
After the excimer laser removes the corneal epithelium, the patient will look into a target that would signal the laser to vaporize the stroma which is the underlying layer of the eye. Today’s technology has allowed eye tracking systems that will prevent the laser from firing if the patient is not looking into the target. The cornea will be reshaped as the laser fires in bursts and the end result should match the pre-operative prescription of the patient. Keep in mind that the depth of vaporization often varies from one person to the next.
To speed up the healing process, a bandage contact lens will be applied to the cornea. A period of one week should be enough to wait for the corneal epithelium to grow. During this period, the patient is expected to feel a slight discomfort, blurriness, and fluctuating vision. To prevent potential bacteria and infection, topical antibiotics and lubricants should be applied to the eyes at regular intervals. This can also help minimize irritation.
As PRK only vaporizes the most external layers of the eye, patients with very thin corneas are suitable for this type of refractive surgery. Additionally, those with low to moderate prescriptions can opt for PRK as an alternative to Lasik. The results of PRK are as good as other types of laser eye treatment which is why many eye specialists still use this type of eye surgery to correct the eyesight.
Credit: PRK New Jersey Photorefractive KeratectomyCredit: PRK New Jersey Photorefractive Keratectomy