Short answer: No, not in the way that matters for your vision. PRK, TransPRK and ASA (advanced surface ablation) are different names for the same operation. In each one, the thin surface layer of the cornea is removed and an excimer laser then reshapes the cornea underneath, without cutting a flap. The laser treatment that corrects your prescription is the same. The only difference is how the surface layer comes off: in TransPRK the laser removes it, and in conventional PRK the surgeon removes it by hand. At Focus Vision the price is the same whichever method your surgeon uses.
If you have been researching laser eye surgery, you have probably seen all three names, sometimes presented as three different procedures, or with ASA described as a newer or premium option. This guide from the corneal surgeons at Focus Vision in Brisbane explains what each term means, the one real difference between them, and how your surgeon decides which method suits your eyes.
What is PRK?
PRK stands for photorefractive keratectomy. It was the first type of laser eye surgery, and it is still widely performed around the world.
The cornea is the clear window at the front of your eye. Its outermost layer, the epithelium, is a thin skin of cells that regrows within days if it is removed. PRK works in three steps:
- The surface layer is removed from the central cornea.
- An excimer laser reshapes the cornea underneath to correct short-sightedness, long-sightedness or astigmatism.
- A bandage contact lens is placed while the surface layer grows back over several days.
Because no flap is cut, PRK and its variations are called surface treatments, or surface ablation.
What is ASA (advanced surface ablation)?
ASA is an umbrella term, not a separate operation. It came into use as excimer lasers improved and as surgeons developed different ways of removing the surface layer. You may see the same treatment described by any of these names:
- PRK (photorefractive keratectomy)
- ASA (advanced surface ablation) or ASLA (advanced surface laser ablation)
- LASEK
- Epi-LASIK
- TransPRK (transepithelial PRK), including brand names such as StreamLight
- Surface laser or no-flap laser
The “advanced” in the name refers to modern laser technology, such as fast eye tracking and refined treatment patterns. Every PRK performed on a current excimer laser uses that technology, so modern PRK is ASA. If a website presents ASA as a newer or premium procedure that is different from PRK, it is describing the same operation under another name.
| Name | How the surface layer is removed | Laser treatment | Flap? |
|---|---|---|---|
| PRK | Surgeon removes it by hand, often after loosening it with a dilute alcohol solution | Excimer laser reshapes the cornea | No |
| LASEK | Loosened with dilute alcohol, folded aside, then laid back | Same | No |
| Epi-LASIK | Lifted off with a blunt separating device | Same | No |
| TransPRK | Removed by the laser itself, in the same continuous treatment | Same | No |
| ASA | Umbrella term covering all of the above | Same | No |
What is TransPRK?
TransPRK, or transepithelial PRK, is PRK in which the laser removes the surface layer as well as reshaping the cornea, in one continuous step. Nothing touches the eye during the treatment. Alcon’s version, which we use at Focus Vision on the WaveLight EX500 laser, is called StreamLight.
The part of the treatment that corrects your prescription is the same as in conventional PRK. TransPRK changes only how the surface layer is removed.
Is TransPRK better than PRK?
Neither is better for everyone. A 2022 meta-analysis pooled 12 studies of 1,711 eyes and found no difference between TransPRK and conventional PRK in uncorrected vision or accuracy, and similar rates of haze. The included studies generally reported faster healing of the surface layer after TransPRK, although only two of the 12 were randomised trials (Alasbali, 2022).
Where TransPRK can help. The laser removes the surface layer in exactly the zone it is about to treat, without any instrument touching the eye, and the whole treatment happens in one step. Some studies report quicker surface healing and less discomfort in the first days.
Where it can be a disadvantage: mitomycin C. Mitomycin C (MMC) is a medication applied to the cornea for a few seconds at the end of surface laser treatment to lower the risk of haze, a faint scarring that can blur vision. The risk of haze rises with the amount of tissue the laser removes, so MMC is only needed once the laser treatment goes beyond a certain depth.
In TransPRK, the laser removes the surface layer as well as reshaping the cornea, so the surface layer counts towards the total amount of tissue the laser removes. That usually takes even a small correction past the point where MMC is needed, although surgeons’ views on this differ. At Focus Vision we use MMC with TransPRK, including for small corrections; in our published series of 205 TransPRK eyes, every eye received MMC 0.02% for 20 seconds (Gunn and Cox, 2024).
In conventional PRK, the surface layer is loosened with a dilute alcohol solution and removed by hand, so the laser only removes the tissue needed to correct your prescription. For a small correction that is very little tissue, the risk of haze is very low, and MMC is not needed.
That matters because MMC, although very effective at preventing haze, also slows the surface cells as they heal. Some surgeons have reported more recurrent corneal erosions when they used MMC routinely (Ocular Surgery News, 2019). A recurrent erosion happens when the surface layer does not stick down firmly and comes loose again, typically causing sudden pain and watering on waking. The evidence here comes mainly from surgeons’ experience rather than trials, but avoiding MMC when it isn’t needed is one reason we may choose conventional PRK for a small correction.
So for some eyes TransPRK is the better choice, and for others conventional PRK is. These are nuanced decisions, and your surgeon makes them after measuring your eyes.
Why would PRK be chosen over LASIK or CLEAR?
Mainly for safety. LASIK creates a thin flap in the cornea, and CLEAR removes a thin disc of tissue through a small opening. PRK cuts no flap, so for the same correction it leaves more of the cornea’s strong deeper tissue untouched.
That can make PRK the safer option for people whose corneas are thinner or a little weaker than average, who may not be suitable for LASIK or CLEAR at all. It can also suit people in contact sports, or in jobs where an eye injury could dislodge a flap, such as the defence force and police.
The cornea weakening and bulging after surgery (ectasia) is rare after any laser procedure. A 2021 systematic review of published cases found that about 95% followed LASIK, and the rate after LASIK was 4.5 times higher than after PRK (Moshirfar et al., 2021).
The trade-off is recovery. After any surface treatment the eye is usually sore for a few days, useful vision typically returns over about a week, and sharpness can keep improving for weeks after that. Our recovery timeline sets out what to expect week by week.
How does your surgeon decide which method to use?
Your surgeon weighs several things, including:
- the size and type of your prescription
- your corneal thickness and shape on detailed scans
- your risk of haze, and whether MMC would be needed
- any previous eye surgery or surface problems, such as past erosions
- your work, sport and lifestyle
You don’t need to choose a technique yourself. Your surgeon will recommend the method they judge best for your eyes and explain why.
Does TransPRK cost more than PRK at Focus Vision?
No. PRK and TransPRK are both $3,500 per eye at Focus Vision, or from $34 a week on a 24-month interest-free plan. The price includes your pre-operative assessments, the procedure and 12 months of follow-up; prescribed medications and eye drops are extra. Because the price is the same, the method is chosen on clinical grounds only. See our costs page for full details.
What results can I expect?
In our published series of 205 eyes treated with StreamLight TransPRK in Brisbane, 95.6% of eyes saw 20/20 or better without glasses and 92.2% finished within 0.50 dioptres of the target prescription, measured at least three months after surgery (Gunn and Cox, 2024). Our TransPRK results page explains the study in plain English. Individual results vary.
What are the risks?
Surface laser has a long safety record, but like any surgery it carries risks, including:
- discomfort for the first few days and a slower visual recovery than LASIK
- haze, which is uncommon and usually fades
- infection, which is rare
- under- or over-correction, which may need a top-up treatment (see our enhancement policy)
- dry eye, glare or halos, usually temporary
- recurrent corneal erosion
Your surgeon will discuss the risks that apply to your eyes before you decide.
The bottom line
PRK, ASA and TransPRK all describe the same laser treatment. What matters is not the name but whether the method suits your eyes, and that comes from a careful assessment by your surgeon. If you’d like to know whether surface laser treatment suits you, book a free optometrist assessment.
References
- Alasbali T. Transepithelial photorefractive keratectomy compared to conventional photorefractive keratectomy: a meta-analysis. J Ophthalmol. 2022;2022:3022672. pubmed.ncbi.nlm.nih.gov/36051276
- Gunn DJ, Cox RA. StreamLight single-step transepithelial photorefractive keratectomy (PRK) for myopia and myopic astigmatism. J Ophthalmol. 2024;2024:5597457. pubmed.ncbi.nlm.nih.gov/39575318
- Moshirfar M, Tukan AN, Bundogji N, et al. Ectasia after corneal refractive surgery: a systematic review. Ophthalmol Ther. 2021;10(4):753-776. pubmed.ncbi.nlm.nih.gov/34417707
- Katsev D, Kontos M. Prophylactic mitomycin with laser treatment may prevent haze but also may delay healing. Ocular Surgery News (Healio). April 2019. healio.com