Small Incision Lenticule Extraction (SMILE) is minimally invasive laser eye surgery that can correct various vision impairments including myopia and astigmatism.
Running on a femtosecond laser, it takes less than 30 seconds to create a lenticule – or small lens-shaped piece of corneal tissue – inside the cornea. The surgeon then removes the lenticule through a small incision on the eye surface, in doing so reshaping the cornea to correct the refractive error.
Launched internationally in 2011, millions of eyes around the world have now been treated with SMILE. For this article we interviewed Sydney ophthalmologist Dr John Males (Envision Eye Centre) about his experience with the technology.
Q. How long have you been undertaking the SMILE procedure and what were the reasons behind first starting to use the technique?
I have been performing SMILE since January 2015. I became aware of SMILE around 2011 and was interested to know more because of the advantages it was purported to offer over the existing corneal laser refractive surgical techniques of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). I was skeptical at first, that a femtosecond laser could achieve the precision required to accurately treat refractive error. As it turns out, refractive precision is one of the strong points of SMILE.
As a corneal surgeon, I was also interested to learn that SMILE has minimal impact on the ocular surface. Issues like dry eye can be problematic after corneal refractive surgery; especially after LASIK which has the greatest impact on corneal nerves. With LASIK I have often found that while many patients enjoy great vision on day one, dry eye can cause their vision to deteriorate, until corneal sensation improves.
SMILE has become an integral part of our laser refractive practice. Happy patients make this a most rewarding procedure to perform
Another disadvantage I saw in LASIK was the need to create a flap, which can dislocate with trauma at any time. While this is uncommon, it can be a consideration for some patients, especially those with careers in the military and people who play contact sports. SMILE appealed because the small incision eliminates the risk of flap dislocation, and yet patients still achieve the rapid visual recovery associated with LASIK.
So SMILE was very interesting to me, as it offered the promise of correcting a large range of myopic refractive errors while having minimal impact on the ocular surface, and delivering rapid visual recovery. Leaving the eye biomechanically stronger, in the absence of a flap, was also appealing.
Q. What were your early experiences in learning to use the SMILE technique – are there any particular challenges ophthalmologists should be aware of?
All new procedures carry a learning curve. With SMILE these can be divided into a number of areas:
SMILE involves centration and docking of the Visumax laser, then the 20 second laser procedure to create the SMILE lenticule, followed by the surgical removal of the SMILE lenticule. The centration and docking process is similar to other femtosecond lasers and is something every refractive surgeon is familiar with. However, the removal of the lenticule is very different to other laser vision correction procedures – it has more in common with lamellar corneal surgical techniques seen in corneal transplantation, for example.
As a corneal surgeon, the step to lenticule extraction was perhaps not as large as for other non-corneal refractive surgeons, but it certainly is a technique that needs to be refined and requires care in the initial stages. In early cases, I would recommend treating moderate myopic refractive errors as the lenticules are easier to handle and remove. Small refractive errors have thin lenticules, which are more prone to tearing or being difficult to remove.
SMILE takes a greater degree of cooperation from the patient than other refractive procedures. It is critical that the patient does not excessively move their eyes or head during the 20 second laser procedure. A large movement or excessive squeezing can result in suction loss, and in some cases, an alternate laser procedure such as PRK may be required. There is a learning curve involved in assessing patients who might find the laser procedure difficult and are, therefore, more suited to alternative approaches. The lenticule dissection also requires a degree of cooperation. A patient who maintains good fixation will help the surgeon complete the procedure more quickly, and will usually have a quicker visual recovery.
Q. What difference does SMILE make in terms of, for example, efficiency, ease of use and logistics in a surgery?
SMILE has been an efficient procedure to integrate into our laser refractive practice. The preoperative process is unchanged with comprehensive history, examination, investigations and counselling over at least two visits.
Surgical time for SMILE is shorter than LASIK and similar to transepithelial PRK – this has received significant positive feedback from our patients.
Most importantly, patients are highly satisfied with their rapid vision recovery, minimal post-operative ocular surface issues, and vision outcomes. Our enhancement rate is 0.8% of all those undergoing SMILE, and lower again for those with low astigmatic refractive errors. The rapid recovery and high satisfaction has allowed us to streamline our post-operative visits for most patients. When we first started to use SMILE, we followed patients routinely for 12 months. After a period of time, we realised little was achieved by the later visits, and patients were keen to not attend if possible. Now, we typically discharge patients to the care of their optometrist after three months.
Q. There is discussion that the SMILE procedure results in less glare compared to other laser surgical techniques, has this been something you have identified with your patients?
Quality of vision is excellent post SMILE. Night vision issues, glare and haloes are very uncommon outside of the early postoperative period. Patient reported outcomes in terms of both quality of vision, glare, haloes, and night vision, are excellent in our experience and in the scientific literature. In our experience, quality of vision improves for at least three months post-operatively, and issues such as glare are rarely problematic or noticeable after this time. The rapid recovery of the ocular surface with SMILE is likely to help the improvement in quality of vision.
Q. What is the patient selection process for SMILE? Are there any patients you would not use it on?
All patients considering a laser vision correction procedure have a comprehensive history, examination, several refractions, investigations including corneal topography, corneal tomography and tear film osmolarity. Patients have at least two pre-operative visits, where they are counselled by our refractive specialist orthoptists and then by the ophthalmologist. We ensure they have enough time to consider their treatment options and to weigh up the relative advantages and disadvantages of the various procedures, or indeed whether to proceed with surgery at all.
Patient selection for SMILE firstly involves the physical characteristics – ensuring adequate corneal thickness, healthy corneal tomography, reasonable tear film and an otherwise healthy examination. The refractive range that can be treated is from -2 to -9D of myopia. I limit astigmatic treatment to approximately 2D, although this may increase with the new platform discussed later.
Secondly, when compared to LASIK or PRK, SMILE does take a greater degree of cooperation from the patient, both during the laser and lenticule removal stages. Occasionally, for particularly anxious patients where cooperation will be difficult, I recommend an alternate procedure.
If there is a greater potential need to adjust the refraction with a second procedure, for example in a patient having monovision where they think they may want to adjust the refraction later, I am more likely to suggest LASIK if possible, as the enhancement process is more straightforward than with SMILE.
We make a point of offering choice in the laser refractive procedures where a patient is suitable for multiple options. For example, a low myope with healthy corneas may be suitable for LASIK, SMILE and PRK, and each will have some advantages and disadvantages. In some cases, I will suggest one procedure only where one procedure offers better overall results. For example, I would recommend SMILE to a high myope with relatively drier eyes, as they are more likely to recover quickly and with greater refractive predictability than with alternative procedures.
Q. Are there any tips for pre- and post-operative care that you would give to optometrists whose patients might be about to undergo SMILE?
Our optometrist colleagues can be most helpful by identifying the patients who have stable refractive errors and are motivated to consider a laser vision correction procedure. Once they have a stable refraction and would like to proceed, it is helpful to optimise the ocular surface prior to consultation and surgery. In particular, soft contact lenses should be avoided for at least three days prior to consultation and surgery. Blepharitis should be treated and, if required, preservative free lubricants for dry eye should be prescribed.
Information about previous refractions, patient expectations and needs are most helpful – patients often have a long standing relationship with their optometrist, who is, therefore, in a good position to evaluate the patient’s visual needs and relay those needs to us in their referral.
Post-operatively, SMILE patients will typically be prescribed topical steroid and antibiotic in the form of Ofloxacin and Dexamethasone, four times daily for seven to 10 days. Copious preservative free lubricants are used in the early post-operative period, then reduced depending on patient symptoms. Those with pre-existing healthy ocular surfaces typically need minimal lubricants after four weeks, while those with some pre-existing dry issues may need increased lubricants greater than their normal usage for a more prolonged period of three to six months.
Patients who experience contact lens intolerance, but are comfortable out of contact lenses, typically have little need for lubricants after the early post-operative period. This is because contact lenses usually produce more ocular surface disturbance than the SMILE procedure.
I encourage our patients to continue their regular reviews with their optometrist post-operatively, both from the perspective of checking their post-operative progress, as well as monitoring their eye health in the longer term. Presbyopia correction in due course is also a consideration.
Post-operative monitoring of visual acuity, ocular surface health, and intraocular pressure is helpful. Use of preservative free lubricants should be encouraged. Taking adequate breaks from screens and near vision tasks in the early post-operative period should be encouraged.
A patient’s optometrist can help us decide whether enhancement may be necessary following SMILE. Fortunately, this is relatively uncommon, and in our clinic is typically performed with transepithelial PRK. While post-operative refraction is a consideration in deciding on the need for enhancement, we will sometimes discuss with patients whether small residual refractive errors require treatment if they are not impacting visual function to any significant degree.
Q. What is some of the feedback you get from patients?
Word of mouth about the SMILE procedure is strong. Many patients come to the clinic based on the experiences of family, friends and colleagues having undergone SMILE. It can be disappointing to explain to some patients they are not suitable for SMILE when they had their heart set on it.
Patient feedback is generally very good. Patients are pleased with the rapid recovery in vision, with most patients easily achieving vision adequate to work and drive the next day. The most popular patient flow is laser on Thursday, a day one post-operative check on Friday and back to work on Monday. Equally popular is the rapid return to normal activities, such as swimming and driving. Almost all patients meet legal driving requirements on the first post-operative day, although we usually recommend caution for a few days. Swimming can resume in three days.
Q. What does the future hold for SMILE?
The next generation of SMILE, with the second generation Visumax Laser, is about to arrive in Australia. We are looking forward to the improvements the new platform will offer.
By building on the strengths that SMILE already offers, this new platform cuts the laser treatment time in half, reducing the disturbance of the ocular surface and reducing the risk of suction loss. The platform offers automated treatment centration, as well as automated compensation for cyclotorsion. Cyclotorsion control will allow greater accuracy in treating astigmatic refractive errors and give greater confidence in treating higher degrees of astigmatism with SMILE.
Further, the new platform offers the promise of further improvements in the future, including the treatment of hypermetropia.
SMILE has become an integral part of our laser refractive practice. Happy patients make this a most rewarding procedure to perform.