PRK vs. ASA vs. LASEK: Is there a difference?

There is a lot of varied content on the internet regarding the merits of ASA (advanced surface ablation) versus PRK (photorefractive keratectomy) versus LASEK (laser-assisted subepithelial keratomileusis). But what do these terms mean? What are the differences, if any? And how do these procedures as a group differ from the more commonly known procedure, LASIK (laser in situ keratomileusis)? We’ll try to clear up the confusion right here and now.

First, while you might be told that ASA is somehow a more advanced form of PRK, the truth is, when it comes to corneal epithelial removal and excimer laser stromal tissue removal, they are the same procedure. When surgeons use the term ASA, they are usually implying that the procedure they’re performing will be customized to that particular patient. But PRK can also be customized, either via a wavefront aberrometer or a topography-guided excimer laser plan. So if a surgeon offers you ASA, what they are usually offering is a custom photorefractive keratectomy (PRK) procedure. But it behooves you as the patient to confirm that your procedure will be customized to your unique eyes and cornea.

Now, let’s get back to why, in terms of the surgeon’s intervention, ASA and PRK are the same. Both entail the removal of corneal surface epithelium by various means available to the surgeon before an excimer laser is used to remove a precise amount of corneal stroma tissue to correct one’s vision.

Your surgeon will generally choose one of three ways to remove the corneal epithelium:

1. An excimer laser

2. Diluted alcohol

3. An Amoils brush

Of these three, I have found that over two decades and over 20,000 surface laser procedures, the Amoils brush provides the most rapid healing of corneal tissue, because it avoids injury to neighboring epithelial cells, which occurs in alcohol-assisted epithelial removal, and it also avoids the additional unnecessary energy absorbed by the cornea in the case of “laser scrape” epithelial removal. However, the Amoils brush has a disposable tip, which costs LASIK eye surgeons more than the other two methods, which is why many surgeons don’t opt for it, but I find it’s well worth it as it provides the patient with a more consistent and more rapid post-op healing experience.

So how does LASEK fit into all this, and is it any different than what I’ve described above?

I’ll give you the technical answer first, and then I’ll tell you what surgeons who perform “LASEK” generally do now. As defined above, LASEK, in its pure form, involves using diluted alcohol to remove the corneal epithelium in one sheet, pushing it to the side so the laser can reshape the stroma (the thick strong layer under the epithelium.)

After the laser, that epithelial sheet is placed back in position over the cornea, and a contact lens is placed over the epithelium, although when LASEK was first introduced in the 1990s, contact lenses were not initially used. It was discovered that the denuded epithelium which was placed back in position over the cornea was generally no longer viable tissue and would become opaque and reduce the clarity of patients’ vision during the healing period, which tended to be longer in classic LASEK because new, vital epithelium was being created underneath the sheet of dead epithelial cells which in effect could create a barrier and impede normal epithelial healing, in addition to that dead tissue having leached out whatever remnants of diluted alcohol might be retained in the original epithelial sheet.

The only advantage that was sometimes gained was in the setting where a contact lens was not available, since for those for whom the epithelial sheet remained in place on the cornea, a reduction of post-operative discomfort was noted for some compared to those who did not have the epithelial sheet replaced over the cornea when no contact lens was available.

The trouble was that when contact lenses were not used, the original epithelial sheet was often found to be displaced to one side or folded, so eventually surgeons began to abandon LASEK in its pure form because of the slower healing and visual recovery along with unpredictable post-operative discomfort. Surgeons concluded that the use of bandage soft contact lenses post surface ablation proved to be superior to any attempts to replace denuded epithelium that had been treated with alcohol.

So what do surgeons who use the term “LASEK” actually do nowadays? Well, to provide predictable healing and reasonably good vision while patients are in their three to four-day healing period, the original epithelial sheet, which is removed from the cornea, must not be replaced; it must be discarded, and the new epithelial tissue is naturally allowed to migrate over the treated cornea unabated underneath a bandage contact lens.

In conclusion, whether a surgeon wants to use the term Advanced Surface Ablation/ASA, LASEK, or PRK, as far as removal of the top layer of the cornea (the epithelium) is concerned, there is no difference, other than how the surgeon chooses to remove that epithelium. Surface laser is a tried-and-true method to correct vision and has been around for over 25 years and is still very popular in the US Air Force, from which I came. While it does take longer to heal and achieve your best vision when compared to LASIK eye surgery in NYC, it has advantages for patients with thin or irregular corneas as well as those with scarring or other corneal trauma, which might make LASIK more risky. It’s also a good option for patients who have a strong blink reflex and have a hard time sitting still under the laser.

Don’t let the terminology surrounding these surface laser options, PRK, ASA, and LASEK, confuse you. They all entail the removal of corneal surface cells (epithelium) and an excimer laser to the stroma underneath.

Hope this clears things up. After all, clarity is what my team and I strive for!