AMARIS Custom PRK
PhotoRefractive Keratectomy or PRK, is a procedure where the treatment of a patient’s prescription is performed by reshaping the outer surface of the eye, rather than the inner layers of their cornea as it is with LASIK. It is the original form of Laser Vision Correction that was first performed in 1987, a few years prior to LASIK. Like all technologies and techniques it has evolved and improved over the past two and a half decades. Today with Advanced Surface Ablation (ASA) customized patterns can be treated providing higher quality vision for nearsightedness, farsightedness and astigmatism.
The PRK procedure begins with the instillation of topical anesthetic eye drops to numb the surface of the eye. The patient is then placed beneath the laser, lying on the laser bed. One eye is covered while the other eye is treated. Patients focus on a small flashing green target light. An eyelid holder is then placed to prevent blinking, and because the eye is anaesthetized, the blink reflex is eliminated. The corneal surface is then marked to delineate the area to be treated with the laser. The epithelium or surface protective layer is then removed. This can be performed with various techniques, including using the laser itself, mechanically with a microsurgical spatula or brush, and chemically, with diluted ethyl alcohol to break the cellular bonds. In the case of AMARIS Custom PRK, it is performed with a ‘No Touch’ approach. Once the eyelid holder is inserted, the AMARIS 750S locks on to the eye, and the laser system removes the epithelial protective layer and corrects the prescription in one continuous treatment profile. Patients may sometimes smell the laser gases and gas particles, which smell like burnt hair, but feel nothing during the laser application. The next step involves the insertion of a bandage contact lens to improve the comfort during epithelial healing which usually takes two to five days. The epithelial layer renews itself every five to seven days, so the central area is usually much faster, especially with the AMARIS ‘No Touch’ approach. Read more...
Custom PRK uses sophisticated measurements, known as wavefront and topographical analysis, to map the prescription and shape of your eye not just centrally from a single central point as with glasses but at hundreds of points across the cornea. This Wavefront pattern is as unique as their fingerprint for that patient, and not only determines how many pulses of laser are required centrally but also peripherally. Wavefront and Topography based treatments are used with both PRK and LASIK, and improve the quality of vision achieved, especially at night. In the past, Standard PRK techniques, which were based upon a single central measurement, created sharp focus centrally but not peripherally leaving many patients with night glare. Crystal Clear Vision™ only utilizes custom laser treatment patterns with the AMARIS 750S Excimer laser system. The AMARIS system actually uses over 1000 points to create the Wavefront map, far more than most systems, to provide greater data accuracy.
The Amaris 750S is able to perform Custom PRK, utilizing the world’s first six dimensional eye tracker. Once locked on to the eye, the system centers the treatment and lasers through the epithelial protective layer in what is termed a transepithelial or ‘No Touch’ approach. The AMARIS 750S is one of the only lasers in the world capable of measuring layers of corneal tissue intra-operatively. The custom surface treatment is then applied seamlessly after the epithelial layer is lasered. Not only does this simplify the procedure for patients, epithelial healing is enhanced, providing PRK patients with a faster visual recovery.
There are many variations of corneal surface treatments beyond PRK, including Epi-LASIK and LASEK, but despite all the techniques and variations, all require the removal of the surface protective layer, known medically as the epithelium. For this reason, LASIK, which preserves the epithelium, has a faster visual recovery time, virtually overnight. LASIK also has a more comfortable recovery and requires less eye drops post-operatively, days instead of months. There is less potential for scarring and infection with LASIK as well. PRK and all surface treatments however require less corneal tissue, so that in patients with thinner corneas or corneal shape changes, PRK is the treatment of choice. PRK also does not require the creation of a corneal flap and therefore is a simpler procedure. In general, the clinical results and visual outcomes of LASIK and PRK are equivalent, however the easier and faster recovery with LASIK has made it the procedure of choice worldwide for most prescriptions.
In conclusion, AMARIS Custom PRK is an advanced form of laser vision correction with clinical results equal to that of AMARIS Custom LASIK, and is performed in about 15% of Crystal Clear Vision™ patients when it is medically determined that the shape or corneal thickness precludes LASIK. Hide...