SMILE (SMall Incision Lenticule Extraction) is a minimally invasive, flapless, keyhole laser eye surgery with higher accuracy, lower risk and better recovery compared to previous generations of laser eye surgery.
SMILE employs focused femtosecond laser incisive pulses delivered directly inside the cornea to create a lenticule and a 2.8mm incision. This lenticule optically represents the patient’s myopia or astigmatism. The lenticule is then extracted through the small incision and the refractive error is thereby corrected.
..laser created lenticule optically represents the patient’s short-sightedness….when removed…the vision is corrected
The key advancement is in the laser technology. The Zeiss femtosecond laser can deliver incisive pulses directly to a focal point inside the cornea. The laser energy does not cause collateral injury before or after the focal point. Typical laser treatment time is 25 seconds regardless of the correction required. There have been over a million successful procedures performed around the world. We are proud to be one of the FIRST clinics to offer SMILE Laser eye surgery in Sydney since 2018.
Internal Lenticule creation
A thin lenticule is created internally inside the intact cornea by the laser. A very small 2.5mm surface laser incision is then made to allow access to this internal lenticle.
The lenticule is removed through the incision with minimal disruption to the corneal biomechanics.
Impairment is corrected
Removing the lenticule changes the shape of the cornea, thereby achieving the desired refractive correction.
A smaller wound always heals faster. Most of the above benefits are related to a much smaller wound with SMILE.
Small incision lenticule extraction, or SMILE for short, is a minimally invasive treatment and requires no ﬂap.
A laser is used to create a thin, contact-lens-shaped layer just beneath the corneal surface and then a small opening
through which that layer is removed. Some studies show that there is less disruption of the corneal surface and
fewer immediate post-operative dry eye symptoms with SMILE as compared to LASIK.
SMILE uses a femtosecond laser which can directly treat within the cornea without collateral injury to the surface of the eye. By using rapid laser pulses and precise three-dimensional control, the laser incises a lens shape (the lenticule) which corresponds to the optical error of a patient’s eye inside the cornea. The laser also creates a very small opening for extraction of this lenticule. The optical error is corrected once the lenticule is removed.
This is unlike the excimer laser used in PRK (1st generation) and LASIK (2nd generation) which requires a large opening to access the inside of the cornea. A corneal flap or epithelium (skin) removal allows this exposure of the inside of the cornea. This is a step that is not required with SMILE. This is a fundamental change in how the treatment is delivered and this innovation is related to many of the clinical advantages with SMILE.
With SMILE, there is only a 2.5mm wound on the surface of the eye, there is minimal discomfort even on the day of surgery. Patients can return to active activities like swimming within 3 days.
SMILE Femtosecond laser lenticule treatments require only 25 seconds regardless of the power of correction required. This is because the lenticule is cut rather than vapourised. The Excimer laser (used in PRK and LASIK treatments), on the other hand, vapourises the cornea like a sander on a wood block. High power correction requires more treatment time (up to 8 minutes depending on the laser and correction required). Excimer lasers (used in PRK and LASIK treatments) are also very sensitive to humidity as the water absorbs the laser energy. The longer treatment time together with sensitivity to environmental factors makes the LASIK or PRK less accurate at higher power corrections.
NO BURNING SMELL
SMILE is odourless as there is no burning. The vapourisation effect of the excimer laser used in PRK or LASIK is the cause of the burning smell some patients notice during PRK or LASIK.
The Zeiss Visumax is currently the only laser system which can perform SMILE because of the precision required. An innovative curved patient interface is used to attach the laser to the patient to minimise tissue distortion to allow low energy and high precision treatment required for SMILE. The associated advantage is minimal discomfort during laser treatment.
The Zeiss Visumax is also currently the fastest femtosecond laser at 500kHz. That is half a million pulses within 1 second. Only 25 seconds is required to create the lenticule.
Corneal Nerves are important for regulation of the tear film of the eye. Transection of these nerves leads to dry eyes until the nerves regrow. The time frame of nerve regeneration is variable. LASIK requires a corneal flap. Nearly all corneal nerves around this flap are cut during LASIK surgery. As a result, dry eye is very common shortly after LASIK. Most patients after LASIK would be significantly better after 6 weeks although there are some patients who never achieve full recovery of their corneal nerves, hence developing long term dry eyes after LASIK.
Dry eyes when severe is similar to the itchy scratchy and blurry vision symptoms one would get when a contact lens irritates the eye. SMILE treatment minimises collateral injury to corneal nerves by being a flap free procedure and also the treatment is applied deeper. Consequently, SMILE surgery has a much lower risk in causing long term dry eyes.
Note the LASIK wound is 10 times larger than the SMILE wound.
The superficial layers of the cornea (Bowman Layer) is the location of the highest tensile strength. It is important to remember that the cornea is part of the structural coat of the eye analogous to the leather on a basketball. Laser corneal surgery weakens the cornea through the laser treatment and structural cuts when a flap is created in LASIK. If the cornea is weakened excessively then it can bulge and stretch leading to damage to vision. This is called ectasia (similar to keratoconus), which is a rare complication for all laser eye surgery.
SMILE treatments are applied deeper and therefore preserving the strength of the cornea. On the other hand, LASIK flaps completely remove the structural strength in this superficial Bowmans Layer. As a result, the risk of ectasia is higher with LASIK compared to SMILE, although the overall risk is still low.
The LASIK corneal flap never completely heals. Direct trauma to the eye can still lift the flap even after 20 years. For patients active in contact sports or patients who have a career in law enforcement or the military, this is an undesirable risk even though the risk is small. Previously, PRK was recommended to these patients despite pain and slow healing. With the availability of SMILE, these patients now have a comfortable option with quick recovery.
SMILE treatment results in a smoother surface on the cornea as the treatment is deeper. More superficial treatments from PRK and LASIK can have a more abrupt change at the edge of the treated area. A smoother peripheral corneal surface reduces the risk of night time halos from less higher order optical aberrations.