Editorial - Reasons to SMILE?

With advantages such as lack of a flap, less incidence of flap-related complications, better retention of biomechanical strength, less dry eye, better and faster recovery of corneal sensation, as well as proven predictability, efficacy and safety, small incision lenticule extraction (SMILE) is slowly establishing itself as a superior means of refractive correction.

Less dependence on external influences such as room temperature and humidity, corneal hydration and other factors, together with faster workflow, are added advantages over LASIK. It’s not therefore surprising that SMILE is steadily gaining in the number of surgeons performing it, as well as the number of patients opting for it over LASIK.

But is it always a win-win situation? As with any new procedure, trade-offs and spin-offs emerge. The initial high investment required, as well as the need to still have a LASIK machine for hyperopic treatments and for patients who cannot afford the generally higher-cost SMILE, are disadvantages.

Though astigmatism has been shown to be tackled effectively with SMILE, there is scope for further improvement with regard to better algorithms and compensation for cyclotorsion. Wavefront-based treatments are not possible. Newer complications, such as partial lenticular retention and implantation of epithelial cells under the cap, can be more difficult to manage, and with constantly increasing numbers being performed, still newer complications may yet be reported.

SPIN-OFFS

Spin-offs that emerge are of course related to the by-product of the SMILE surgery – a beautifully carved lenticule of precise dimensions obtained from a cornea in its normal physiological state and hydration. The possibilities this offers are many and it has been utilised by researchers to substitute synthetic inlays, which have disadvantages related to biocompatibility and oxygen and nutrition diffusion across the cornea.

All tissue additive techniques employ implantation of a precise lenticule as an allograft for refractive correction. Jod Mehta was the first to implant SMILE lenticules into animal eyes. Ganesh et al used it for the treatment of hyperopia and keratoconus. I have personally used it as a PrEsbyopic Allogenic Refractive Lenticule (PEARL) inlay for the treatment of presbyopia, with very good results, because of increased depth-of-focus secondary to induced hyperprolacity. Unlike most presbyopic inlays, the extremely small size (1mm) gives a normal surrounding zone within the pupil for largely unaffected distance vision.

Reported good outcomes by Mehta, Ganesh and Sun, as well as good results in my own personal experience, may indeed be the beginning of the re-emergence of highly precise additive treatment technology as originally envisioned by José Barraquer. Technological advancements will help make these inlays non-antigenic, further increasing the safety profile.

To summarise, SMILE is bringing forth new possibilities in refractive treatment as well as in other areas. Improving machines and algorithms contribute to constantly improving results. Will it completely replace LASIK eventually? One cannot say. Will techniques such as PEARL become widely adopted? Again, only time can tell.

However, one thing is for certain – the future is exciting and I look forward to it, as I am sure do all eye care practitioners everywhere, to seeing where this technique will eventually take us.