By reading this section you will gain an understanding of what PRK is.
Figure 1. Removing the epithelium
WHAT IS PRK ?
LASIK is an acronym which stands for P
It was the first laser refractive procedure which has been largely replaced by LASIK.
I recent years there has been a resurgence of PRK and it is still performed in certain circumstances.
DIFFERENCE FROM LASIK
In LASIK, a flap is created using a microkeratome or with Intralase. Then the laser is applied to the corneal stroma. Finally, the flap is put back.
In PRK, there is no flap. Instead the epithelium is removed, usually with a blunt knife or with alcohol and then the laser is applied directly to the corneal surface. The epithelium grows back covering the lasered area.
Figure 2. Removing the epithelium with alcohol
PROBLEMS WITH PRK
PRK is an excellent procedure but suffers from two main problems.
Firstly, good vision is not seen straight away but instead can take weeks. This is unlike LASIK which usually results in excellent vision even the next day.
Secondly, it can be uncomfortable and even painful.
To minimise pain, usually a contact lens is worn until the epithelium grows back which can take several days.
WHEN IS IT BEST TO USE PRK
Most surgeons will perform PRK if the amount of correction required is small.
Also,in patients who have thin corneas, PRK may be the only option.
This is because the flap in LASIK is about 120 microns and contributes little to structural integrity.
In PRK there is no flap so 120 microns is saved. As a rule, a cornea with less than 500 microns in thickness is usually better of with PRK.
One of the biggest problems with PRK was haze. Since the advent of topical Mitomicyn C (MMC) this has become less of an issue.
Figure 3. Apply the laser