PKR : Surface refractive photokeratectomy
Surface refractive photoablation with the excimer laser (PRK) consists of correcting optical defects of the eye by polishing the surface of the cornea with the excimer laser, which makes it possible to restore a corneal curvature that allows the light rays to focus correctly on the retina, and in so doing eliminates myopia, astigmatism, hyperopia or presbyopia. The PRK technique is therefore performed just on the surface of the cornea, without creating a corneal flap beforehand, unlike Lasik. More than 30 million cases have benefited from this method since 1990 (30 to 60% of surgical cases), a method for which we have more than 30 years of experience.
The procedure usually takes around 5 minutes per eye, and is painless.
The procedure is usually performed as follows
Surface anaesthesia with an eye drop. Patient is awake but no pain is felt. The patient looks into a fixation light and sees nothing else.
Peeling of the corneal epithelium with a spatula/ethanol.
Polishing of the corneal surface with the Excimer Laser. The patient stares at the flashing light which aligns the eye. An infrared tracking system realigns the laser 400 times per second to compensate for eye movements (eye-tracker). Each laser strike removes 0.25 microns (a quarter of a millimetre) of surface corneal tissue, sculpting the cornea to the desired curvature change. The surgeon then applies a specific product (mitomycin C) with a small sponge to control the postoperative healing and avoid scar regression (haze)
A non-corrective bandage lens and antibiotic eye drops are applied to the eye at the end of the operation.
The lens is removed after 5 days by the ophthalmologist
Indications
Experienced surgeons prefer PRK in the following cases:
- Moderate myopia (less than -6.00 dioptres)
- Very thin cornea (less than 500 microns)
- Young candidates (under 25 years of age)
- Risk of corneal trauma (combat sports, exposed professions)
- Pathological cornea (scarring, previous radial keratotomy, recurrent epithelial erosions, subclinical keratoconus…)
Advantages of PRK
- Simplicity: PRK is technically relatively simple, and does not require the creation of a corneal flap, which avoids the potential complications of corneal flap creation. The procedure is also faster.
- Safety: PRK is considered statistically the safest method of laser refractive surgery (no flap problems, reduced postoperative dryness problems)
- Effectiveness: the visual results of PRK are the same as those of Lasik for myopia of less than 6.00 dioptres
- Combined treatment: PRK allows simultaneous treatment of a pre-existing corneal anomaly: Therapeutic photokeratectomy of recurrent epithelial erosions or corneal scarring (PTK) Topography-guided photoablation of corneal deformity (keratoconus)
Cost: the cost of PRK is lower than Lasik.
The disadvantages
Le risque de complication infectieuse est très rare, ce qui nécessite donc une surveillance stricte postopératoire les premiers jours
- The postoperative comfort of PRK is less good than that of Lasik. Postoperative irritation is experienced for a few days, with some blurring of vision. Pain is sometimes present for 1 to 3 days. The treatments (drops, analgesic tablets, sleeping pills for the first night, contact lens dressings) are generally very effective and the majority of patients only complain of discomfort (discomfort in the light, tearing, sensation of sand in the eye).
- The recovery time for vision is longer. 4 to 7 days on average, 1 – 3 months for the optimal result.
The risk of an infectious complication is very rare, so strict postoperative monitoring is required for the first few days.
Laser Eye Surgery procedures are performed at Focus Eye Clinic in Brussels by Dr Qin
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