All about Lasik and other Refractive Surgeries - Suitability for Lasik, Standard vs Customised Lasik, Blade-less Lasik, Femto Lasik, Contoura Vision Lasik, iLasik, Risks of Lasik surgery, SMILE, ReLex SMILE, PRK, ICL
What is LASIK surgery and how will it affect my vision? What are the alternatives to LASIK?
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.
What is the difference between various types of LASIK Surgeries - 100% blade-free Femto LASIK, All-laser LASIK, Robotic LASIK, iLASIK, Contoura vision LASIK, Customized LASIK, etc.?
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.
After the laser ablation reshapes the cornea, the flap is then laid back in place, covering the area where the corneal tissue was removed. The flap seals to the underlying cornea during the healing period following surgery.
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
Femto LASIK, 100% blade-free LASIK, All-laser LASIK, Robotic LASIK are all essentially same. As explained above, they all use a Femtosecond laser to make the corneal flap in Step 1 of the LASIK procedure.
Contoura vision is a brand of Alcon which is a division of Novartis. It is a topography-guided Custom LASIK.
iLASIK is the name of the LASIK platform of J&J. It utilizes wavefront-guided technologies for Custom LASIK.
What is SMILE / ReLEx SMILE? Is it a type of LASIK?
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.
Am I a fit candidate for LASIK Surgery? What if I am not a fit candidate – are there other options for me?
Generally, you are a suitable candidate for LASIK if
you are more than 18 years old,
your spectacle power is stable for at least a year,
your Corneal Thickness is more than 500 microns and
your Retina is healthy.
Doctors may not recommend LASIK if you
have autoimmune disorders, such as rheumatoid arthritis
have a weakened immune system caused by immunosuppressive medications or HIV
have severe myopia (nearsightedness), very large pupils or certain eye diseases such as persistent dry eyes, keratoconus, keratitis, uveitis, herpes simplex affecting the eye area, glaucoma, cataracts, eye injuries or lid disorders, etc.
participate in contact sports that may be associated with blows to the face
If you don't meet the criteria for LASIK you may be able to go for
PRK (Photo Refractive Keratectomy) also know as Surface Ablation or
ICL (Implantable Collamer Lens)
What is PRK? How is it different from LASIK?
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
No risk of corneal flap complications
Since no flap is created, depth of laser treatment in PRK is less than in LASIK and therefore strength of the cornea is better after PRK surgery.
Takes longer to heal compared to LASIK and is painful for the first few days
Because the ablated cornea is exposed (since no flap) there is higher risk of infection till cornea heals. To take care of this, a bandage contact lens is placed on the cornea for a few days till the cornea heals.
What is ICL?
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.
Does LASIK , PRK etc. completely eliminate the need for spectacles or contact lenses?
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.
What are the major risks of LASIK Surgery?
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.
Risks of LASIK include:
Dry eyes: LASIK surgery causes a temporary decrease in tear production. For the first six months or so after your surgery, your eyes may feel unusually dry as they heal. Dry eyes can reduce the quality of your vision. Your eye doctor might recommend that you use eyedrops during this time. If you experience severe dry eyes, you could opt for another procedure to get special plugs put in your tear ducts to prevent your tears from draining away from the surface of your eyes.
Glare, halos and double vision: After surgery you may have difficulty seeing at night. You might notice glare, halos around bright lights or double vision. This generally lasts a few days to a few weeks. Even when a good visual result is measured under standard testing conditions, your vision in dim light (such as at dusk or in fog) may be reduced to a greater degree after the surgery than before the surgery.
Under-corrections: If the laser removes too little tissue from your eye, you won't get the clearer vision results you were hoping for. Under-corrections are more common for people who are nearsighted. You may need another LASIK procedure within a year to remove more tissue.
Over-corrections: It's also possible that the laser will remove too much tissue from your eye. Over-corrections may be more difficult to fix than under-corrections.
Astigmatism: Astigmatism can be caused by uneven tissue removal. It may require additional surgery, glasses or contact lenses.
Flap problems: Folding back or removing the flap from the front of your eye during surgery can cause complications, including infection and excess tears. The outermost corneal tissue layer (epithelium) may grow abnormally underneath the flap during the healing process.
Vision loss or changes: Rarely, you may experience loss of vision due to surgical complications. Some people also may not see as sharply or clearly as previously.
Have more questions about Lasik? Schedule a consultation with our Lasik Specialist Dr. Aditi Agarwal
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.