Small incision lenticule extraction (SMILE) was heavily discussed at the recently held Annual Conference of Delhi Ophthalmological Society (DOSCON 2019) in New Delhi, India. Ophthalmic surgeons in India, who have transitioned from laser-assisted in situ keratomileusis (LASIK) to SMILE, not only discussed the pros and cons of the procedure, but also shared clinical pearls to get the best outcomes in SMILE.
“In transitioning from LASIK to SMILE, each surgeon had issues with SMILE in the beginning,” said Dr. Radhika Tandon, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences (AIIMS), New Delhi. “The mental readjustment to this new procedure is equally important,” noted Dr. Tandon.
The surgical learning curve is not that difficult, according to Dr. Tandon, but the step-by-step procedure (i.e., from docking to femtosecond laser delivery) should be worked on slowly with patients to get the best outcomes. “More importantly, read, read, read, and listen to what everybody says,” she emphasized.
Apart from visual acuity (VA), contrast sensitivity is a more reliable parameter in assessing visual performance following any refractive procedure, reported Dr. Ananth D of Lotus Eye Hospital and Institute, Tamil Nadu and Kerala, India. In LASIK, he said, there have been reports of at least temporary losses of contrast sensitivity, and this loss may persist six to 12 months postoperatively.
In a prospective, observational study of myopic patients (100 eyes, 50 patients) who underwent SMILE procedure at the Lotus Eye Hospital and Institute, Dr. Ananth’s team found that most patients (84 out of 100 eyes) achieved the preoperative contrast sensitivity within three months following the procedure, while the rest of the patients (16 of 100) did so in six months. There was no significant difference found in contrast sensitivity after six months. Also, at six months to one year postoperatively, no significant difference was noted in contrast sensitivity at any spatial frequency. These results, according to Dr. Ananth, showed that correction of myopic refractive error using SMILE provided statistically significant favorable results, not just in terms of visual acuity but also in terms of the time taken to regain quality of vision (contrast sensitivity).
“SMILE is LASIK without a flap and photorefractive keratectomy (PRK) without pain,” said Dr. Shilpa Singh, consultant at Visitech Eye Centre, New Delhi, India. That statement, according to Dr. Singh, summarizes the benefits of SMILE: minimally invasive, flapless, use cutting instead of ablation.
“The biggest advantage of the procedure is having no flap, and therefore no flap-related complications,” she emphasized. However, the disadvantages, noted Dr. Singh, is that there is a learning curve to be overcome and that SMILE currently cannot treat hyperopia. While the learning curve cannot be truly called a disadvantage, the bigger consideration is the cost of the procedure.
While SMILE and FS-LASIK are comparable in efficacy, safety and predictability in correcting myopia, the loss of biochemical effects may occur less frequently after SMILE than after FS-LASIK. On the other hand, reported Dr. Singh, SMILE may have superior aberrations compared to FS-LASIK in some cases. “A small percentage of SMILE patients can have prolonged recovery compared to those who had LASIK. Also, there are some reports of microdistortions in the Bowman’s layer after SMILE, which may account for delayed recovery,” Dr. Singh added.
“Though we have had multiple studies comparing the dry eye incidence, patient satisfaction, refractive error correction in the two procedures, we are yet to reach a conclusion whether one procedure has a definite edge over the other,” explained Dr. Singh.
“The only thing which almost all studies agree with is that SMILE definitely has a better rate of subjective satisfaction among patients in the immediate postoperative period, especially with respect to dry eye compared with LASIK,” she said. “We still need more studies and data analysis to reach a conclusion as to which procedure is better,” Dr. Singh concluded.
But is SMILE a game changer? It definitely is, according to Dr. Chitra Ramamurthy from The Eye Foundation, Coimbatore, India. It’s major ‘attractions’ being an all-in-one solution with fewer variables and a small learning curve, she highlighted.
“Uncertainties have always been the breeding ground for newer technologies,” said Dr. Ramamurthy. As is the case in SMILE, that the uncertainties of previous technologies have brought this procedure forward. “
Although the biomechanics is still a bit of a mystery, but even if SMILE needs more tissue, it still leaves the cornea stronger than LASIK,” said Dr. Ramamurthy. There are still limits of correction to SMILE (i.e., no mixed astigmatism correction yet, not for the treatment of hyperopia yet), and in small refractive errors, SMILE can be a challenge, she added.
In refractive outcomes, every parameter is a toss between LASIK and SMILE. LASIK has been around for more than 20 years, while surgeons are still continuously learning about SMILE. “Learning SMILE is an art in itself. It gives us a greater interest in doing refractive surgery. But knowing the rules of the game raises the bar in getting optimum refractive outcomes,” advised Dr. Ramamurthy.
On the other hand, for Dr. Gaurav Luthra of Drishti Eye Institute & Dehradun Wave LASIK Centre, Dehradun, India, to make the best of both worlds, he uses either SMILE or LASIK, depending on the type of patient. He reported that SMILE is more preferred for myopes from 2-10 DS, myopic astigmatism up to 3 D CYL, sportspersons (or professions with higher risk of trauma), borderline dry eye and those seeking faster physical rehabilitation and lesser precautions. While LASIK, he noted, is for hyperopes and pure/mixed astigmatism, high astigmatism, those seeking faster visual recovery, topography guided or wavefront customized treatments, and those who cannot afford SMILE.
Guided by such criteria, Dr. Gaurav believes that no one modality is perfect for every situation. “All modalities — PRK, LASIK, SMILE — have a place in the refractive surgeon’s armamentarium. While SMILE is emerging as the preferred option for a significant chunk of cases, PRK and LASIK still have a role in many situations,” he highlighted.
However, once hyperopic SMILE becomes available, indications for LASIK may go down. “That, and a larger long-term data on the biomechanical superiority of SMILE, may tilt the table further,” he concluded.
Editor’s Note: DOSCON 2019 was held at The Hotel Ashok in New Delhi, India, from April 12 to 14, 2019. Media MICE Pte. Ltd., CAKE Magazine’s parent company, was the official media partner at DOSCON 2019. Reporting for this story also took place at DOSCON 2019.