|Photo-Refractive Keratectomy (PRK): How the Surgery is Performed|
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How is Excimer PRK surgery performed?
As with incisional refractive surgical procedures, the first step for a prospective candidate is a comprehensive eye evaluation including a careful measurement of myopia and corneal topographic analysis( See Incisional Procedures).
The patient is placed beneath the laser delivery system and a brief training session given in which the individual learns to fixate upon a light during the PRK procedure and the laser is briefly activated to acquaint the patient with the sound and sensation of the treatment. The eye is anesthetized with topical drops which render the procedure completely painless.
Once good alignment and training have been accomplished the operating surgeon will mark and central 7.00 mm zone upon the corneal surface and will manually remove the superficial corneal cells(epithelium) with a blunt polishing instrument. The laser is programmed and delivers the precise number of pulses required to achieve the amount of corneal flattening desired in 30 to 60 seconds . In many instances both eyes are treated consecutively in one sitting. After the photoablation is completed, the surgeon will place a bandage soft contact lens upon the eye and instill topical antibiotic and anti inflammatory drops. The patient leaves the treatment center without a patch.
Is the surgery painful?
Following excimer laser surgery, most patients can expect to experience a moderate amount of discomfort and light sensitivity- on an individual basis. This is anticipated and can be controlled with topical drops and pain medication by mouth. Most pain will pass within a period of 24 hours and patients will note only mild irritation and foreign body sensation thereafter which will pass spontaneously in the course of one week.
What can a patient expect following PRK surgery?
The bandage contact lens which is placed upon the cornea at the time of surgery is usually removed at two to three days post operatively. Its function is to promote epithelial (surface cell) healing and ocular comfort. Patients are given topical antibiotic drops for a period of 7-10 days and a tapering schedule of mild anti inflammatory drops over 3 month to discourage the development of corneal haziness or clouding which could have an adverse effect on the ultimate visual outcome.
In the immediate period following surgery vision is blurry and will remain so until the opening wave of epithelial healing has occurred and corneal swelling has passed. Other post operative symptoms include double vision or ghost vision and tearing. Within a week to ten days visual acuity will begin to clear rapidly and continues to improve and stabilize over the ensuing two to three months.
What are the possible long-term side effects of laser refractive surgery?
Glare/Haze- Although this does not seem to have an effect on long term visual outcome, a small number of patients can develop corneal haze. In some this haze can be significant although it will usually fade and can be effectively treated with topically applied anti-inflammatory medications. This more commonly results in glare--difficulty in seeing well in the face of bright lights at night.
Loss of Spectacle Correction- Approximately 6% of patients can have a visual outcome which leaves them below their best correction before surgery. In other words, a patient who had acuity of 20/20 with glasses or contact lenses, might have uncorrected 20/25 acuity after surgery which may not be further correctable with glasses or contact lenses.
Improper Correction- An occasional patient can have a result which leaves them under corrected and requiring the continued use of glasses or contact lenses. Under corrected patients can be retreated after a suitable waiting period. Likewise it is possible in a small number of patients to experience an over or under correction. Laser vision correction is a reliable precise system for visual correction making this unlikely especially with careful measurement of refractive error performed prior to surgery.
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