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Jan 8

2015

Know Everything About PRK Method Eye Surgery (Photorefractive Keratectomy)

Modern medical science uses laser beams to correct vision related problems.  Photorefractive keratectomy (PRK) has treated millions of patients so far, and it is one of the popular corrective laser surgeries.

What is photorefractive keratectomy (PRK)?

Among various vision corrective surgical procedures, Photorefractive keratectomy (PRK) changes the shape of the cornea for correcting focal length. Surgeons use Excimer Laser beam to remove very thin layer of the cornea. Though LASIK appears to be a similar procedure, there is a slight difference. Surgeons create a flap in the latter instead of removing a layer. PRK achieves a large number of refractive errors restoring the vision back to normal. Myopia (near sightedness), Hyperopia (far sightedness) and astigmatism are to name a few. Other refraction irregularities can also be corrected with a high precision.

Firstly, surgeon removes the central part of the cornea with a buffing instrument or a blunt knife.  A fine computer-controlled laser beam works in the form of pulses removing a microscopic part of corneal tissue in a particular pattern. A contact lens is placed on the cornea to protect the exposed cornea from the eye infection. As the cells grow eventually after a few days, doctors remove the soft contact lens.

It is relatively simple and quick surgery that gets over in 15 to 20 minutes. Doctors give mild sedative to make patients comfortable and relaxed. After applying numbing drops, surgeons use a lid speculum to keep the eyelids open. Programmed laser beam corrects the vision within a few minutes. A little bit of pressure is felt on the eye during the process.  Doctors perform it on each eye separately but consecutively depending on the willingness of the patient. Some people prefer a gap of two weeks between the two.

How do doctors decide whether the patient is suitable for it?

Doctors check the softness of corneal tissue before opting for the procedure. Apart from it, thickness of the cornea is another critical aspect. Since there is a fine layer gets removed during the procedure, sufficient residual corneal tissues must be there to achieve vision correction without any risk.  Eyes should be free from inherent underlying problems that affect the stability, clarity or ability of healing of the cornea.  Detailed examination and investigation are carried out before the procedure.  Any abnormality or adversity may eventually reject the person. Refractive error correction is never performed for kids or teenagers since the eye is still in a developing stage. If the PRK procedure is performed before refractive stability, it may result in under correction (where the patient has to wear specs in spite of surgery).

PRK and LASIK, the critical difference

  • PRK is typically the predecessor for LASIK surgery. It is advantageous in some cases where LASIK is not suitable. PRK takes a longer time to heal up. The outcome is almost comparable though. Also, there is a higher risk of eye infection and haziness of vision during the first few days of the surgery.

  • It reshapes the cornea, so that light enters with a proper angle to get focused on the retina for better and clearer vision. In LASIK procedure, doctors remove a thin flap to work on the area where laser beam works. In PRK, they remove epithelial or outer layer without any flap. In both surgeries, stomal layer gets sculpted using powerful laser beam.

  • In the case of LASIK, doctors preserve the epithelial layer till the surgery is over. The same layer is attached to the outer layer after surgery. Since there is no flap created, and there is no need of regenerating outer as well as inner tissues, the entire cornea is available for quick restoration.

  • PRK is advantageous where the cornea is inherently thin or in patients who have already undergone LASIK procedure earlier.

Post-operative care and risks

Doctors advise a rest of few hours after the surgical procedure. Though the operation does not cause severe pain, they want to keep the patient under observation.  Someone else must take the patient to home. Topical antibiotics are prescribed for faster healing, supported by anti-inflammatory drugs. Mild painkillers are given to reduce the pain and discomfort. Patients are supposed to follow doctor’s advice in order to achieve optimum results. Follow-up appoints are scheduled for a few weeks to monitor the healing progress and vision correction. Since PRK recovery takes a longer time as compared to LASIK, it may take a few days to a few weeks for total vision restoration and eyesight improvement. However, daily routine can be resumed after a few days. Even driving is allowed after three to four weeks.

Very unlikely patients develop post-operative complications like glare, starbursts or halos while looking at illuminated objects. In some patients, there may be a need of enhancement surgery for further vision improvement. Sometimes, vision gets deteriorated over a period, and surgeons have to perform another round of surgery. Age-related deterioration can’t be avoided, and patients have to go for reading glasses after 40’s.

Long-term results

PRK is an effective eye surgery with quite an impressive success rate. There have been advancements in the last two decades making it a treatment of choice for certain patients. In the majority of patients, 20x20 vision is achieved. Almost 100 percent patients achieve 20x40 or better visual accuracy. Some patients may be recommended with specs or contacts, but with very less power.

Pre-operative checks

Eye surgeons carry out a variety of tests before going for the procedure.  Along with a thorough eye examination, there are a number of investigative tests to determine the suitability for the laser treatment. Size of pupils, moistness of eyes, corneal curvature and thickness, and contours of the front surface of the eye are important parameters. There is a special apparatus used for measurement. General health and medical background screening are done for assessing capability of coping up rapidly after surgery.  People taking special medication, having allergic history and diabetes are examined further critically. Those who wear contact lenses are supposed to stop wearing them for some time before pre-operative checks are conducted because contacts change the natural shape of the cornea.