PTK, phototherapeutic keratectomy, excimer laser, cornea - A State of Sight #17

PTK can be performed with laser to remove corneal scars, smooth uneven corneal surfaces, or decrease the recurrence of corneal erosions. Details in this episode of A State of Sight with Isaac Porter, MD.

Welcome to A State of Sight, I’m Isaac Porter and this is your weekly update in ophthalmology and eye care from Raleigh, NC. In this episode, I would like to explain PTK, or phototherapeutic keratectomy, which is a laser procedure which can improve a patient’s vision if they have a problem with their cornea.
Remember, the cornea is the clear shield that covers over the front of the eye and to better understand this procedure, first we need to know how the laser works since we use the same laser that we perform LASIK to perform PTK (the excimer laser).
Every pulse from the laser removes a set amount of tissue from the cornea when it impacts the tissue. When patients are nearsighted, the laser is programmed to flatten the cornea and remove more of the cornea in the center to change the curvature and include the power needed in glasses onto the eye.
Due to the way that the laser removes tissue, we can use the same laser to remove the front layers of the cornea in order to make it more clear. Depending on the depth of the scar or pathology of the cornea, the laser can be set in a predetermined manner to remove a certain amount of tissue.
PRK is a laser procedure similar to LASIK that doesn’t involve creating a flap. Instead, we first remove the cells from the surface of the cornea and then treat the remaining cornea with the laser to change the shape. The thin layer that is removed is called the epithelium, and it is similar to our skin since it changes over and is replaced after it is removed.
PTK is similar to PRK because we also remove the epithelium (surface cells) from the cornea and then place the laser onto the remaining cornea.
This is primarily used for three different problems of the cornea: recurrent corneal erosion syndrome, corneal scars, or an irregular cornea.
In the last episode, we covered recurrent corneal erosion syndrome that can cause a breakdown of the surface of the cornea. This can occur after a patient has had a corneal abrasion and may cause recurrent pain and redness of the eye.
PTK can treat this by removing a few layers from the cornea. Once the epithelium or the surface heals back over, it can have better adhesion and prevent recurrent breakdowns.
Corneal scars can be treated with PTK if they are in the very front part of the cornea. We may need to remove more tissue when we remove the scar, so we may have to go deeper and take away more layers. If the scar is near the surface, we can often remove it and leave a clear cornea behind. In scars that extend deeper, we do not always have to remove all of the scar, but by removing part of it, vision can be improved in some cases.
In other people that have an irregular cornea with an uneven surface including bumps or ridges in the cornea, PTK can be used to smooth out the surface and improve vision.

If you have any questions about these diseases or the procedure PTK, please post and we will be happy to answer them. Until next time on A State of Sight, good health and good sight.