Astigmatic Keratotomy and Photo Refractive Keratectomy

There are four main refractive surgical techniques currently available around the world:

These incisions are normally 90 to 95% of the thickness of the cornea and cause a reduction in the curve of the central cornea for the myopic eye. RK surgery has been found to have some limitations including fluctuation in vision and starbursts. Complications at the time of surgery, such as perforation, an irregular incision and infection are rare, but can be serious. In the USA and worldwide the use of RK in all its forms has rapidly declined.

Astigmatic keratotomy (AK) is a treatment normally used to treat astigmatism. AK surgical incisions are made as arcs in the corneal periphery.

PRK is applied to the central (optical zone) of the cornea to reduce its curvature. A modern excimer laser used for PRK sculpts an area 6.0 or more millimetres in diameter on the surface of the eye.

Vision is normally blurred for a few days after treatment. There may be a temporary apparent over correction towards hyperopia (long sight) with treatment for myopia and toward near sight for treatment of hyperopia. This is normal and later the over correction disappears in most patients.

PRK Treatment to One Eye Only 

Spectacle lens wearers who undertake PRK to the first eye must be aware that there may be difficulties in vision until the second eye is treated. If for any reason the second eye is not treated there may be continuing difficulties.

Mild discomfort after treatment that can be controlled by the use of analgesic (pain relieving) medications

• The clarity of vision can be reduced during this healing stage

• Infection or abscess of the cornea before the surface corneal epithelial cells have healed

• Reduced quality of vision due to cornea being an irregular shape

• Glare or starbursts around lights, due to the treatment zone being irregular or of a size smaller than the pupil of the eye when dilated in dim lighting conditions (especially night driving)

• Over correction or under-correction

• Induced astigmatism due to surgery

• Regression of refractive outcome that may need re-treatment

• Reduction in contrast perception

• Imbalance if only one eye is treated

• Episodes of pricking or dryness occur

• Reactivation of Herpes virus infection of the cornea

• "Melting of the cornea" if there is a collagen autoimmune disease

• Altered fitting of contact lenses, should they be required, due to the changed shape of the cornea

• Haze formation over the treated area of the cornea

• Drooping eyelid due to steroid drops or inflammation

• Astigmatism may be over-corrected resulting in a change in axis of close to 90 degrees

PRK for Hyperopia (H-PRK)

Technique

• Those complications associated with myopic PRK are to be expected with hyperopic PRK 

• Recurrent erosion syndrome due to the large area of corneal epithelium removed. This causes prickling or dry eye symptoms which often occur on awaking in the morning

• Increased time for the epithelium of the cornea to heal (4 to 8 days) and hence increased duration of pain or discomfort

• Regression to hyperopia again

• Over correction to become myopic