Photorefractive Keratectomy (PRK) Procedure

The eye is made numb with anaesthetic eye drops and the eyelids held apart with and eyelid speculum.
The front cell layer of the cornea (epithelium) is removed using either a spatula, a rotating brush or with ethanol.
The excimer laser is used directly on the front surface of the cornea to effect the reshaping.
We normally place a soft disposable contact lens on the eye to relieve pain. With modern high water content contact lenses there is typically only mild pain and about 50% have no significant pain. Antibiotic eye drops are used to prevent infection.
After PRK it takes about 4-5 days for the front cell layer to heal up. Eye drops similar to aspirin can be used if required to provide pain relief.
It takes about 7-10 days to achieve clear vision and full stabilisation takes 3-6 months.
Visual results are at least as good as LASIK for low to moderate amounts of myopia. Over -6 dioptres of myopia there is less accuracy and more chance of regression.
The development of haze in the cornea is the most serious problem with PRK, although this has reduced with more modern scanning spot excimer lasers such as the Bausch & Lomb Zyoptix 100 laser.

Leaves more corneal tissue untouched, making it safer if the cornea is thin.
Almost no long-term risk of developing keratectasia (bulging cornea).
Proven to have no visually significant complications after 10 years of follow up.
None of the possible flap-related complications of LASIK.
The structural strength of the cornea is not significantly altered.

Can be painful in the 2-3 days afterwards (although this is much less of a problem that it was in the past)
May take 7-10 days to achieve clear vision, requiring up to a week off work.
Some people develop a pronounced healing response in the cornea leading to deposition of new tissue. This causes corneal haze.
Not very predictable results in higher myopia or high astigmatism.