If you’re a glasses or contact lens wearer and have been doing your own research into laser eye surgery, you may have come across a technique known as SMILE eye surgery. While laser eye surgery methods such as LASIK and PRK are more well-known, SMILE eye surgery is still relatively uncommon and not quite as widely known. To find out more about what is SMILE eye surgery, keep on reading.
What is SMILE Eye Surgery?
SMILE is an acronym standing for small incision lenticule extraction. As with all laser eye surgery techniques, it surgically corrects vision by adjusting the shape of the cornea, which is the clear dome covering the coloured iris at the front surface of the eye. By changing the corneal curvature, light is bent, or refracted, through the eye in such a way that it can come to a sharp focus right on the retina, thereby providing clear sight.
SMILE eye surgery involves using a femtosecond laser to separate a disc-shaped piece of inner corneal tissue, known as a lenticule, without needing to remove the outer layers of the cornea. Prior to undergoing the operation, the lenticule will have been carefully calculated in its shape and size according to the biometric measurements of your eye and its prescription. Once formed with the femtosecond laser, the lenticule can then be removed through a tiny keyhole incision, resulting in the cornea being reshaped from the inside with minimal disturbance to the rest of this structure.
As with the other laser eye surgery techniques, SMILE eye surgery is a day procedure performed under topical anaesthetic. Both eyes are typically treated at the same time. Currently, SMILE eye surgery is able to correct prescriptions of up to:
- -10 dioptres of myopia, also known as nearsightedness or short-sightedness
- -5 dioptres of astigmatism
At the moment, SMILE eye surgery is not commonly used for treating hyperopia (also known as long or far sightedness). Several studies have investigated the application of SMILE for these eyes and have concluded that it appears to be a promising laser eye surgery option, but there is not yet enough long-term data for refractive surgeons to recommend using it routinely to correct hyperopia.
What is SMILE Eye Surgery Best For?
Studies have demonstrated that the SMILE technique offers visual results that are no worse than those achieved with LASIK and PRK. These results encompass both final visual acuity (clarity of sight) and the residual prescription of the eyes remaining after treatment. In terms of the safety of the SMILE laser eye surgery method, it’s generally considered to be highly safe. However, studies have noted that (unsurprisingly), more complications may occur with less experienced refractive surgeons as they’re learning this technique.
In addition to providing visual results equivalent to those achieved with LASIK and PRK, SMILE eye surgery carries some advantages over these laser eye surgery techniques. One study noted that SMILE actually provided patients with a more accurate prescription correction than LASIK. Furthermore, LASIK was found to be more often associated with post-treatment myopic regression compared to eyes undergoing SMILE. This occurs when an eye starts to return to short-sightedness after having been treated with laser eye surgery.
When compared to PRK, SMILE is thought to provide better safety and increased patient satisfaction due to minimal discomfort in the post-operative healing period and faster recovery of sight. However, when compared to LASIK, the visual recovery after SMILE tends to be relatively slower.
A significant advantage of SMILE laser eye surgery is a reduced risk of dry eye symptoms postoperatively, which can be a common problem after LASIK. As the SMILE technique means the corneal nerves are less disrupted compared to other forms of laser vision correction, this causes less disturbance to the neural pathways involved in tear production.
Researchers have also investigated the impact of SMILE on corneal biomechanics. Not all studies came to the same conclusion, however, there is the suggestion that the strength and integrity of the cornea are better retained after treatment with SMILE compared to LASIK or PRK. These biomechanical changes are also often found to be more predictable with SMILE than with other laser vision correction procedures.
What is the SMILE Eye Surgery Eligibility Criterion?
If SMILE eye surgery sounds appealing, there are a few eligibility criteria you need to meet to ensure it is a safe and effective operation for you. These can be assessed and discussed with your eye surgeon. If you’re found not to be quite suitable for SMILE, your surgeon may be able to offer you a different laser surgery technique that will be better. In general, people may be suitable for SMILE eye surgery if they:
- Are at least 21 years old
- Have a stable prescription that has not changed for at least the past 12 months
- Have a prescription within the range treatable with SMILE
- Do not have any other eye conditions that will significantly limit the results of treatment, such as progressing cataracts or a lazy eye
- Are not pregnant or breastfeeding at the time
- Do not have any medical conditions that may slow healing or increase the risk of complications, such as uncontrolled diabetes
If you’re interested in SMILE eye surgery, speak to your optometrist about the possibility of a referral to a refractive surgeon.
Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.
References
Refractive lenticule extraction small incision lenticule extraction: A new refractive surgery paradigm.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5778540/
SMILE laser eye surgery.
https://www.allaboutvision.com/visionsurgery/smile.htm
Small incision lenticule extraction (SMILE) for hyperopia: 12-month refractive and visual outcomes.
https://journals.healio.com/doi/abs/10.3928/1081597X-20190529-01
What is small incision lenticule extraction?
https://www.aao.org/eye-health/treatments/what-is-small-incision-lenticule-extraction
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