Recent advances in excimer laser technology provide us with the most accurate technique for “cutting” of the human cornea and therefore changing the shape of the cornea. We often use the excimer laser for refractive purposes, but there are some less performed techniques for treating irregular corneal surfaces. 

Corneal surface irregularity is more detrimental to vision than corneal opacity. Consider the options mentioned on how one could potentially smooth that irregularity or opacity, with a fast, easy, safe and accurate procedure: the therapeutic corneal laser.


What Procedure Types Are There?

Before even looking at the actual laser, consider that we have laser application options onto the cornea. The type of procedure is dependent on whether the epithelium is included or not with laser ablation.

The epithelium is manually removed, sometimes with the help of alcohol or a brush. The laser is then applied to the exposed stromal bed. The refractive equivalent of this procedure is a PRK, PhotoRefractive Keratectomy.

With this procedure the laser is applied straight to the epithelium and then stroma without pause. The epithelium acts as a masking agent. The refractive equivalent of this procedure is a TransPRK (Transepithelial PhotoRefractive Keratectomy).

Fluid is used as masking agent to smooth the stromal bed. Usually done after one of the other therapeutic profiles, or after removal of the epithelium alone.

This is a combination of multiple Wavefront / Topography guided profiles. First, a TransPTK / PTK is done. Then a WetPTK to smooth the stromal bed. The eye is remeasured immediately. A new custom PTK profile is planned, and steps one and two are repeated. The process can be repeated a few times, usually 3 or 4 times, but even up to 5 times or more is possible, all in one setting.

We can either go through the epithelial (TransPTK or Transepithelial Phototherapeutic Keratectomy profiles), as well as directly onto the stroma (traditional PTK or Phototherapeutic Keratectomy) after epithelial removal. Both techniques have their merits and indications. Both techniques change shape on a “global” corneal scale. 

We can also laser onto a masking fluid, the so called WetPTK. With this technique, energy is applied to the masking fluid that has been added to the stromal bed, and the energy is dispersed laterally instead of straight down into the stroma. Small “localized” vertical ridges are smoothed with this technique.

I almost always perform the WetPTK after any therapeutic laser, to smooth the bed as much as possible. This has two functions: one, to improve the stromal irregularity as much as possible, but two, to give the epithelium a smooth pathway to close quicker. This means, I do two laser runs on the same eye at the same setting. The so called “Dry Run”, where I apply the calculated profile that will give me global reduction in stromal irregularity. And the “Wet Run” that will smooth the stromal bed of small and localized irregularities. I plan the Dry Run on the eye (within the planning file) that I am operating on, and the Wet Run on the contralateral eye (within the same planning file) so that I do not have to switch to a new planning file in between the two runs on the same eye.

What Profile Shapes Can We Laser?

Any depth can be planned, from 1µm upward. It is not only the depth that can be manipulated, but also the profile shape which we laser. Profiles include:

Therapeutic laser techniques then combine the different profiles with the different corneal applications. The technique chosen is completely dependent on the pathology.

What Pathologies Can We Perform Therapeutic Lasers On?

1. Irregularities

2. Opacities or Scars

3. Recurrent Corneal Erosions. 

4. Corneal Dystrophies

5. Corneal Degenerations

6. Apical Syndrome.

7. Keratoconus and Ectasias