Author: Dr Val Phua MBBS, MMed (Ophth), FRCOphth, FAMS
Photo by: Tim Gouw
If you are doing your research on procedures that can correct your vision, you would have come across SMILE (Small Incision Lenticule Extraction) surgery. SMILE is a popular procedure to achieve freedom from glasses and contact lenses, but how does it compare with the more established LASIK? A quick search may leave you overwhelmed with information about each surgery so here is a quick guide to help you make an informed choice.
LASIK is the most well known procedure for laser vision correction. Surgery itself is quick, requiring only 10-15 minutes per eye and recovery is with minimal discomfort. It is able to treat common refractive errors including myopia (short-sightedness), hyperopia (long-sightedness), astigmatism and can even be used to address presbyopia.
Before proceeding for LASIK, a thorough assessment must be done. The aim in a LASIK assessment is to determine firstly whether or not you qualify for laser vision correction and also which procedure is best for you. This would involve taking a thorough ophthalmic history, detailed eye examination as well as specialised tests that look at the curvature of the eye.
For a start, candidates should be more than 18 years old, not pregnant or nursing, in good general health with no diseases affecting the body such as uncontrolled diabetes or autoimmune disease or requiring certain medications which can affect wound healing such as accutane. The eye should also be healthy with no significant eye diseases like severe dry eyes, keratoconus, advanced glaucoma, advanced age related macular degeneration and infections like herpes simplex or herpes zoster. The degree in the eye should also be stable for the past year and the pupils should not be too big as this would increase the risk of having glare and halos after surgery. A thorough history taking and eye examination would easily check if you meet the above list of requirements.
Specialised tests are also conducted to reveal finer changes in the eye that are not detected by examination. This includes assessing the exact amount of refractive error in the eye, the thickness of the cornea and the regularity of astigmatism. Candidates with irregular astigmatism are generally disqualified from laser vision correction. Some candidates with high degrees of myopia and thin corneas may also be disqualified as the amount of reshaping of the cornea that needs to be done with the laser makes it unsafe. If you fall into this category, don’t worry, your hope of glasses or contact lens freedom is not crushed because there are alternative options including the implantable contact lens (ICL). Candidates who wear contact lenses for long hours a day should lay off the contact lens for a period of time before going for the assessment because use of contact lenses changes the shape of the cornea. For those wearing soft lenses this can range for about 3-7days and for those wearing hard lenses this can be about 2-3 weeks.
As the day of your surgery arrives, many will feel a mix of hopeful anticipation as well as anxiety. Remember that you should not be wearing contact lenses in the lead up to this point. Turn up at your appointed time slot in comfortable clothes and although the procedure itself is quick, you should set aside about 2 hours for the entire process. There are no restrictions on food and drink prior to the procedure. It is also prudent to make arrangements for transport home after the procedure. Before entering the laser suite, your eyelids and lashes will be cleaned and antibiotic eye drops will be given.
Numbing eye drops are given to make you comfortable throughout the procedure, and the eyelids are held open with a small clip. The eye is then held firmly by a machine while a laser is applied to create the LASIK flap. During this time you will feel a pressure on the eye but don’t worry, it will be over in less than 30 seconds. This flap is then lifted and the eye prepared for the corrective laser. The corrective laser reshapes the cornea in seconds depending on the magnitude of the degree in the eye and the flap is then placed back on. A bandage contact lens is applied and the clip removed. The steps are then repeated for the other eye. The entire process takes about 15 minutes.
What about post-surgical care?
Some mild discomfort and a foreign body sensation is common in the early post-operative period so don’t be alarmed if you feel as if there is something in your eye. Some may also find the eyes more sensitive to light and will be more comfortable with sunglasses. Protective goggles are given to prevent accidental rubbing of the eye while sleeping. Antibiotic and steroid eye drops are given for about a week to prevent infection and aid healing. Most patients experience minimal discomfort with some even going back to work the very next day. In the first week of recovery, avoid rubbing your eyes and vigorous exercise. Other activities like swimming and even diving can be safely resumed after 1 month of recovery. During this early phase of recovery, it is common to experience dry eye symptoms. Use the lubricating eye drops liberally to minimise discomfort. The eyes do continue to heal over the ensuing months and you can expect the vision to get slightly better with some time.
Overall, with femto-LASIK, patients recover quickly with minimal downtime, keeping any disruptions to work or planned holidays within a very manageable window.
SMILE (Small Incision Lenticule Extraction) is a newer technique for laser vision correction compared with LASIK and it is able to correct both myopia as well as astigmatism. It is minimally invasive, utilizing only a 3mm wound for the entire procedure.
Before proceeding for SMILE, a thorough assessment must be done. The aim in the assessment is to determine firstly whether or not you qualify for laser vision correction and also which procedure is best for you. This would involve taking a thorough ophthalmic history, detailed eye examination as well as specialised tests that look at the curvature of the eye.
What can you expect during the surgery?
This procedure begins with numbing eye drops given and the eye held in position by a vacuum. It then involves using the femto-second laser to shape a thin disc of corneal tissue (lenticule) from the internal layers of the cornea. This part of the procedure is painless and is done within seconds. This lenticule is then manually dissected and removed from a small side opening.
Unlike LASIK, there is no LASIK flap created in this procedure and the recovery is also fast and with minimal discomfort. The absence of a flap carries with it inherent advantages including leaving a slightly stronger cornea to reduce the risk of further shape changes, avoiding flap related complications like folds within the flap, less dry eye and interface inflammation.
However there remains a small risk of having to convert to the more time tested means of laser vision correction should there be suction loss during the procedure preventing an effective application of the femto-second laser to create the lenticule. The current platform on which SMILE can be performed also does not have an eye tracker to correct for torsion which may occur when the patient goes from a sitting to a lying position. This may make correcting astigmatism slightly less accurate compared with the LASIK procedure. SMILE also currently cannot be used for patients with long-sightedness and if future “touch ups” or enhancements are needed, the more time tested procedures may have to be employed. The visual outcomes of SMILE is comparable with LASIK although the recovery to achieve good uncorrected vision takes slightly longer compared with LASIK.
Overall SMILE is a safe and effective method for addressing myopia and astigmatism. It offers the advantage of a flap-free laser vision correction but visual recovery may take slightly longer with the above listed limitations.