The Cornea is the transparent front part of the eye that helps focus light to create an image on the retina (which is at the back of the eye). When the shape of the Cornea is not perfect the image on the retina is out-of-focus (blurred) or distorted. These imperfections in the focusing power of the eye are called Refractive Errors. Refractive Errors such as Myopia (nearsightedness), Hyperopia (farsightedness) and Astigmatism can be corrected with eyeglasses or contact lenses. The other alternative is Refractive Surgery which reshapes the Cornea itself to improve the focusing power of the eye.
LASIK (laser-assisted in situ keratomileusis), also known as laser eye operation, is a type of Refractive Surgery in which an excimer laser is used to precisely change the shape of the Cornea to improve vision.
SMILE, PRK, ICL are other types of Refractive Surgeries (explained later) which are alternatives to LASIK for improving vision. Your eye surgeon can help you choose the best procedure for your eyes.
All LASIK surgeries are essentially a 3 step procedure
LASIK surgeon creates a very thin, superficial flap in the cornea. The flap is hinged on one side.
The surgeon then folds back the hinged flap created in step 1 to access the underlying cornea (called the stroma) and removes microscopic amounts of tissue from the cornea using an Excimer Laser. This process is called “ablation”. This is the step where the cornea is reshaped to correct the refractive errors so that light entering the eye focuses more accurately on the retina for improved vision.
Various types of LASIK surgeries are differentiated in how they accomplish Step 1 and Step 2 of the LASIK procedure as explained above.
Blade vs Bladeless Lasik
This comes into play in the 1st step of the LASIK procedure i.e. during the creation of the thin, superficial flap in your cornea. In bladeless surgery a Femto Laser (different from the Excimer Laser used in Step 2) is used for creating the corneal flap whereas in conventional/blade LASIK surgery a microkeratome (which is a computer controlled precision surgical blade) is used for creating the corneal flap. While Femto Laser offers higher precision and is able to create a somewhat thinner flap, it is significantly more expensive. It is worth noting that nowadays with SBK (sub-Bowman keratomileusis) microkeratome, surgeons are able to create a thin-flap very close in thinness to what Femto Laser achieves without the high cost of Femto Laser.
Standard vs Customized Lasik
This comes into play in the 2nd step of the LASIK procedure i.e. during the ablation of the stroma. In standard/conventional LASIK, only the lower order aberrations of the eye such as myopia (nearsightedness), hyperopia (farsightedness), and regular astigmatism are corrected – essentially what is in your eyeglass prescription.
Customized LASIK uses much more detailed information about the eye to program the excimer laser that reshapes your eye during the LASIK procedure and hence higher order aberrations (HOAs) affecting your vision are also corrected, leading to somewhat better outcomes.
In Customized LASIK, data points are collected from hundreds of separate reference points on the front surface of the eye which are used to create a detailed map of the refractive error and focusing imperfections of the eye including the higher-order aberrations across the entire cornea. This map is then used to program the excimer laser to deliver a personalized vision correction for your specific needs. There are three basic types of custom LASIK procedures: Wavefront-optimized, Wavefront guided and Topography-guided.
Please note that higher order aberrations are a relatively small component, comprising about 10-15% of the eye’s total aberrations. Low order aberrations account for approximately 85-90% of the overall aberrations in the eye.
As far as the LASIK jargon is concerned
No, SMILE / ReLEx SMILE is technically not LASIK. It is a different type of Laser Eye Surgery to correct myopia (nearsightedness) that is similar to LASIK. In SMILE there is no flap creation (which is why it is often advertised as “flapless” LASIK) and there is no Excimer Laser. SMILE currently is used primarily to treat only nearsightedness and it cannot correct higher order aberrations that is possible with, say a Contoura vision customized LASIK.
SMILE is an acronym for SMall Incision Lenticule Extraction. In the SMILE procedure, the surgeon uses a femtosecond laser to create a small, lens-shaped bit of tissue (lenticule) within the cornea. Then, with the same laser, a small arc-shaped incision is made in the surface of the cornea, and the surgeon extracts the lenticule through this incision and discards it. With the tiny lenticule removed, the shape of the cornea is altered, correcting nearsightedness.
SMILE laser eye surgery can correct up to -10.00 diopters (D) of nearsightedness. Candidates must be at least 22 years old, have no more than -0.50 D of astigmatism, and their eyeglass prescription must be stable for at least 12 months.
Generally, you are a suitable candidate for LASIK if
Doctors may not recommend LASIK if you
If you don’t meet the criteria for LASIK you may be able to go for
Like LASIK, PRK (Photorefractive Keratectomy) is also a type of refractive surgery in which an excimer laser is used to precisely change the shape of the cornea to improve vision. The main difference between PRK and LASIK is in the first step of the procedures. As explained above, in LASIK, a thin flap is created on the cornea with a microkeratome or a femtosecond laser. This flap is lifted to expose the underlying corneal tissue and is replaced after the cornea is reshaped with an excimer laser. In PRK, the thin outer layer of the cornea (epithelium) is removed – no flap is created – and then excimer laser is used to reshape the cornea similar to LASIK. The epithelium repairs itself (grows back over the corneal surface) within a few days after surgery. The depth of the epithelium that is removed is much less than the depth that is used to create a flap which is why PRK is suitable for people with thin corneas.
The final results of PRK surgery are very similar to LASIK outcomes. PRK has some advantages and disadvantages vis-à-vis LASIK.
ICL (Implantable Collamer Lens), a type of Phakic Intra-Ocular Lens (IOL), is an alternative to LASIK and PRK eye surgery for correcting moderate to severe myopia (nearsightedness), and in some cases produce better and more predictable vision outcomes than laser refractive surgery.
ICL is an implantable lens that is surgically placed just behind the Iris in front of the natural lens. Implantable lenses function like contact lenses to correct nearsightedness. The difference is that ICL works from within your eye instead of sitting on the surface of your eye.
While LASIK, PRK and other laser vision correction procedures have very high success rates, not everyone achieves perfect 6/6 vision, although the majority of people experience greatly improved vision after the surgery. The need for eyeglasses or contact lenses, even if not fully eliminated, is still greatly reduced. Your results depend a great deal on the unique way your corneas respond to laser energy and how your eyes heal after surgery.
If you do not get the desired outcome from your LASIK surgery, it may be possible to get a follow-up laser procedure called an enhancement. Your ophthalmologist can assess your suitability for enhancement based on how well your Cornea healed and how thick your Cornea is.
As with any surgical procedure, LASIK surgery has its risks. With modern technology, this procedure is generally safe and produces good results, however, there is a possibility of unsuccessful results and complications, from both known and unknown causes.
Disclaimer: All information, provided above is for informational purposes only and is not intended to serve as a substitute for the consultation, diagnosis, and/or medical treatment of a qualified physician or healthcare provider. Read our full disclaimer here.
