Posted on November 30, 2017
What is Touchless LASIK or SupraLASIK?
Touchless LASIK or SupraLASIK is a kind of Advanced Surface Ablation or ASA, used to offer freedom from glasses to patients suffering from myopia, hypermetropia and astigmatism. It is a surface laser procedure that uses a laser to remove the surface epithelial cells of the cornea to explore the deeper tissue called stroma.
The epithelium is like the skin of the cornea that protects its deeper layers, and is also responsible for maintaining vision. In Photorefractive keratotomy, or PRK, this epithelium is removed manually using alcohol, while Touchless LASIK uses a laser to debride the epithelium.
What is LASIK?
LASIK, on the other hand, does NOT remove the epithelium. In fact, a layer of the epithelium along with the underlying stroma is raised as a thin flap, to expose the underlying tissue. Understanding this vital first step is critical in deciding which surgery to choose for your eyes.
The second step, in which the excimer laser ablates the stromal tissue to the reshape of the cornea to treat the refractive error is common to all three procedures.
What are the disadvantages of Touchless LASIK?
The epithelium, when removed, requires three to five days to grow back in case of Touchless LASIK, exactly as after Photorefractive Keratotomy. This is the period of moderate post-operative discomfort which is variably described by patients as pain, discomfort, and foreign body sensation. In fact, even though there is no head-to-head trail that compares PRK to Touchless LASIK, but most surgeons agree that the postoperative discomfort is similar after both procedures.
This requires the use of a bandage contact lens, for a variable period of three to five days, until the epithelium grows back completely. During this period the patient cannot indulge in usual activities including work and recreation, and is also advised to not drive, due to poor vision. Most doctors counsel patients about this surgical “down time” and are wary of patients’ morale dropping as the promised crystal clear vision requires additional waiting. In fact, In most cases, patients notice an improvement in their vision within the first few days after surgery, but doctors always clarify that the full results will develop gradually over the course of approximately 3-6 months.
In LASIK, however, the epithelium and stroma are positioned back at the end of surgery, and not removed. It is for this reason that patients of LASIK and all its variants report a greater degree of postoperative comfort, and tend to recover vision almost immediately after surgery.
The other problem associated with the surface ablation (PRK and Touchless LASIk or SupraLASIK) is the increase in corneal haze with treatment of higher refractive errors. This is because the epithelium cells can never be removed completely, by either alcohol, or laser, and these tend to grow more haphazardly. This results in a haze in the cornea, which can be distressing to the patient.
There is also an increased risk of infectious keratitis or corneal ulcer with surface ablation compared to LASIK due to the longer epithelial healing period since the protective epithelium has been removed.
Despite these obvious disadvantages, why are surface ablations still in use?
Surface ablation may be preferable to LASIK in patients with epithelial basement membrane disease and in patients who have had corneal surgery before, like corneal grafts.
They were thought to offer a distinct advantage in patients with thin corneas, but with new technologies for LASIK, this is no longer true.
Myths regarding LASIK and ASA ( PRK, LASEK, epi LASIK, SupraLASIK in Thin Corneas:
In fact, in a head to head trail to dispel this myth, Daniel Durrie MD and Stephen Slade MD that compared wavefront-guided thinflap LASIK (SBK with a femtosecond lasercreated 100 micron, 8.5mm flap) and advanced surface ablation in fellow eyes of 50 bilaterally operated patients. They showed that at follow-up visits through the first month after surgery, the advanced surface ablation procedure was associated with more pain and lower patient satisfaction. Also, the visual outcomes were significantly better in the LASIK eyes on the first day after surgery and remained so for at least three months
The newer LASIK machines like the wave front guided LASIK and Contoura Vision Topography Guided LASIK correct the vision based on the eye’s unique attributes, and enable the creation of thinner, narrower, and planar flaps, just like femtosecond laser LASIK. These thin flaps allow stromal ablation in even patients with thin corneas with great efficacy and safety. Most doctors agree that thinner flaps (100 µm) have a better postop visual acuity compared with thicker flaps as well. The Contoura Vision Topography Guided LASIK in fact provides better quality of vision that any other laser refractive procedure, in patients with thin corneas also.
Also, most doctors are also now aware of the fact that patients with thinner corneas are NOT more susceptible to ectasia or protrusion of the cornea, since the thinner corneas have altered biomechanics, making hem stronger. In fact, the most important risk factor for ectasia is keratoconus (disease and forme fruste) which must be ruled out before any laser refractive procedure. Both LASIK and ASA are contraindicated in patients with keratoconus.
So what is the verdict for thin corneas?
The newer LASIK technologies like Wavefront guided LASIK and Contoura Vision Topography Guided LASIK and femtosecond laser ALSIK offer a quicker recovery time, and the patient is more comfortable immediately after the surgery. It has a lesser incidence of post operative complications like corneal haze and infections. Which is why the first choice for patients with thin corneas is NOT an advanced surface ablation of any kind, including touchless LASIK.
ASA variants (PRK, LASEK, EpiLASIK, Touchless LASIK and SupraLASIK) have a very limited role in the armamentarium of the refractive surgeon, since most patients with thin corneas will benefit greatly from the newer advanced LASIK technologies.