When it comes to comparing transPRK to LASIK today, things have certainly changed. Modern bladeless and touch-free transPRK is not comparable to the original PRK method from the 1990s. Also, a transPRK is safer than LASIK surgery.
Fifteen years ago, when our chief surgeon Prof. Farhad Hafezi performed refractive surgery, 90% of the time it would be LASIK, and only 10% of the time it would be PRK. Today, that ratio is completely the opposite. We can (and do) perform both, using the latest equipment, as we have all of the lasers and other equipment needed to do it. So why the change?
The answer is simple: science. TransPRK today is very different to the technique that was known as “PRK” in the early 1990s, and our understanding of the cornea – and what laser refractive surgery does to the cornea – is far more advanced nowadays. When it comes to insight into these changes, we are fortunate to have Prof. Hafezi, who has not only performed the procedure and has seen how it has changed in the clinic, but who also leads an ocular cell biology research group at the University of Zurich, meaning that he has insight all the way from the “molecules to man”.
Let us debunk some of the myths around modern PRK.
One of the advantages LASIK once had over PRK was that it caused less pain in the few days after surgery, but that isn’t the case thanks to advances in modern pain management over the last 15-30 years. When we see patients 24 hours after surgery that just had one eye operated on, the sclera is as white as the non-operated eye, and patients either report little to no pain. It’s also worth noting that Trans-PRK avoids the scraping away of the corneal epithelium with a blade. Today’s Trans-PRK doesn’t even touch the cornea with anything other than laser energy (“bladeless surgery”).
This is no longer the case. Our latest-generation SCHWIND AMARIS excimer laser is light years ahead of lasers from the early 2000s. The technology has advanced so much in terms of how it ablates the cornea; transPRK with the AMARIS now leaves a far smoother surface which causes less inflammation and results in a faster healing response. It also means that visual recovery is considerably more rapid than before: typically, our patients see up to 60% on day 2, and often reach even 80-100% on day 4.
TransPRK is just as effective as LASIK in correcting your vision (it uses the same excimer laser after all). But the most important reason why we prefer transPRK is the fact that it leaves a stronger cornea. It’s all about safety. And a transPRK is safer than LASIK surgery.
Advantages explained
There is no debate: we have performed and published the results of the experiments that prove it (see our posts at the bottom of this page). PRK leaves the cornea stronger than LASIK. Removing corneal tissue with a laser does weaken it – but normally, the cornea has lots of strength to spare. LASIK involves making a flap in the cornea (much like a tin-opener does with a can of beans) which exposes the lower part of the cornea, which then gets lasered. The flap is repositioned – but once cut, it no longer contributes to the strength of the cornea. In PRK, the laser starts ablating tissue at the surface of the cornea – no flap is required, and we know from our objective experimental work published in prestigious peer-reviewed journals that this leaves the cornea stronger.
1. Spiru B, Kling S, Hafezi F, and Sekundo W, Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes: Femtosecond Laser-Assisted LASIK Versus SMILE. J Refract Surg, 2018. 34(6): p. 419-423.
2. Spiru B, Kling S, Hafezi F, and Sekundo W, Biomechanical Differences Between Femtosecond Lenticule Extraction (FLEx) and Small Incision Lenticule Extraction (SmILE) Tested by 2D-Extensometry in Ex Vivo Porcine Eyes. Invest Ophthalmol Vis Sci, 2017. 58(5): p. 2591-2595.
3. Kling S, Spiru B, Hafezi F, and Sekundo W, Biomechanical Weakening of Different Re-treatment Options After Small Incision Lenticule Extraction (SMILE). J Refract Surg, 2017. 33(3): p. 193-198.
One of the most feared complications of laser refractive surgery is “ectasia” – where the cornea is weakened too much by the surgery, to a point where it struggles to contain the pressurized contents of the eye. The cornea starts to bulge progressively, making vision worse and worse. Ninety percent of the time, it’s LASIK that is responsible for this, not PRK. We have been instrumental in developing a treatment, corneal cross-linking, that treats this, but we are firmly of the belief that it’s better not to cause it in the first place. As Hippocrates said: “First, do no harm.”
All of these laser refractive procedures are very safe. The risk of problems (sight-threatening or otherwise) is very small. Nevertheless, we feel that if you can avoid the risk, why take the risk? This is why, unless there are good reasons to perform a different procedure, we believe Trans-PRK is the best solution for most patients. It offers the best-possible vision correction – along with LASIK – but it leaves the cornea stronger for the rest of your life, leaving you with a more stable correction, with a much lower risk of ectasia.
