PRK technology

The PRK technique (medical term: photorefractive keratectomy) is the oldest method of laser eye surgery. This technique removes a thin layer of cells from the surface of the eye, allowing the laser to model the underlying cornea. It offers an alternative for people who have a lower corneal thickness and are therefore ineligible for laser eye surgery using the Femto-LASIK procedure

PRK technique

In the course of the PRK method, only a very thin cell layer of the cornea (= the epithelium) is wetted with a weak alcohol solution and then pushed to the side with a spatula, and is ultimately completely removed and not reused. 

The surgeon has two options for removing the epithelium: 

  • Manual PRK technique: After applying a suitable medical solution, the epithelium is scraped away or removed with a scalpel. 
  • Fully laser-assisted or transepithelial PRK technique: The epithelium is removed using an excimer laser.

As soon as the eye is exposed, the cornea is shaped using a laser to enable light rays entering the eye to be precisely focused on the retina. Finally, a protective lens is placed onto the eye, which remains there until the epithelium grows back – usually within a few days. The full recovery of vision usually occurs after about one month, but it may take longer in some cases. 

The PRK technique is often considered equivalent to the LASIK procedure, but the two methods differ slightly in the first step: while the epithelium is completely removed and not reused as part of the PKR technique, the tissue is returned to its original position after surgery in the case of LASIK surgery. However, both methods follow the same surgical procedure. 

Who is it suitable for?

As with all ophthalmological topics, the PRK technique first involves a discussion with the ophthalmologist treating the patient, which explores suitable solutions for your visual impairment and explains the advantages and disadvantages of the different laser eye treatment methods. 

After performing some tests, the ophthalmologist is able to tell patients whether their refractive error can be corrected using the PRK procedure. Of course, the PRK treatment method that best suits the individual needs of the patient will then be selected in consultation with the ophthalmologist. 

The PRK procedure is fundamentally suitable for many people, as it can be performed even with thin corneal tissue. 

Exclusion criteria for laser eye correction using the PRK technique are 

  • pre-existing eye disease (glaucoma, cataract)  
  • age below 18 years 
  • insufficient corneal thickness (a certain residual corneal thickness must be present after surgery to ensure the stability of the eye)  
  • pregnancy/breastfeeding 
  • unstable refractive values (i.e. refractive error changes continuously)  

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Ophthalmic surgeons advise their patients not to wear hard contact lenses for at least four weeks before the operation or soft contact lenses for at least two weeks before the operation (contact lenses may affect the diagnostic tests carried out before the operation). 

Laser eye correction using PRK procedures takes an average of 10 to 15 minutes and is performed on an outpatient basis using anaesthetic eye drops (local anaesthesia). 

  1. Anaesthesia of the eye using anaesthetic drops 
  2. Insertion of an eyelid retainer to prevent the eye being treated from blinking 
  3. Wetting of the cornea with alcohol 
  4. Complete removal of the epithelium with a special instrument (spatula, scalpel)  
  5. Modelling of the corneal tissue using a computer-guided laser to correct defective vision; the excimer laser is equipped with an eye-tracking system to track and, if necessary, compensate for the movements of the eyes during the procedure. 
  6. Insertion of a protective contact lens, which supports the healing process and improves the patient’s well-being 
  7. Repetition of the process in the other eye 

Laser surgery in Switzerland in our centres

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It is important that patients observe the following after the operation: 

  • Use of eye drops to moisturise the eyes and reduce the risk of infection 
  • Avoiding rubbing the eyes 
  • Plenty of rest, little exertion 
  • No participation in strenuous contact sport for at least one week 
  • Wearing a sleep plaster for at least one week 

Follow-up appointments with an ophthalmologist usually take place one day and seven days, one month and thee months after the operation. A further check-up appointment is then scheduled one month after the procedure. 


What are the advantages of the TransPRK technique?

The TransPRK procedure – the further development of the PRK technique – is much gentler, since the eye does not come into contact with mechanical instruments. Instead, the uppermost layer of the cornea (i.e. the layer of the cornea that is not suitable for laser eye surgery) is removed minimally and without contact, thanks to state-of-the-art laser technology, which makes this technique many times more precise.  

Should both eyes be operated on in the same day?

As it takes 10 to 15 minutes per eye to perform PRK technique, it is advisable to perform the procedure on both eyes on the same day, as this means less strain on the patient. 

Is laser correction using the PRK technique painful?

As an anaesthetic in the form of eye drops is applied to the eye for the procedure, which makes the corneal surface numb, the patient feels nothing for the entire duration of the procedure. After surgery, patients often describe a 'sandy sensation' in their eyes, although this sensation subsides after a few days.

What are the advantages?

The major advantage of the PRK technique is that it removes the uppermost layer of the cornea and avoids the creation of a flap, as is the case with the Femto-LASIK process. The method can also be used if the corneal layer is thin: the PRK procedure is an alternative procedure for patients for whom the Femto-LASIK procedure is not an option due to having a thin cornea.

What are the risks and side effects?

The biggest disadvantage of the PRK technique is its safety profile, because the conventional PRK method has the following disadvantages compared with other laser eye procedures: 

  • significant pain for up to about four days after the procedure
  • an increased risk of infection 
  • and slow recovery of vision over a period of four to six weeks 

The cornea may become cloudy after the operation. Unclear vision or scarring is also one of the major postoperative risks associated with PRK treatment. The milky cloudiness of the cornea can be treated with eye drops and usually does not become a permanent condition. 

It is also possible that the eyes will feel hard, uncomfortable and even itchy after the operation. This is due to the fact that it takes around five days for a new cell layer to grow back. As soon as this has happened, the ophthalmologist can remove the protective contact lens. 

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