SMILE vs LASIK

SMILE (small incision lenticule extraction) has experienced increased adoption in Australia and New Zealand for myopic laser vision correction in the last twelve months. Professor Gerard Sutton (Vision Eye Institute) and Dr. Dean Corbett (Auckland Eye) presented their clinics’ early post-operative results, with data from their first 328 eyes and 90 eyes respectively. “Early results look promising, with the predictability of SMILE as good as LASIK” said Dr. Corbett.

Guest speaker, Dr. Sri Ganesh from Nethradama Eye Hospital in Bangalore, India, shared his clinical studies, having completed over 3000 SMILE treatments since 2012.

He presented post-operative results of his first 1000 eyes treated with SMILE. “97 per cent achieved UCVA 6/6 or better at one day post op, with 64 per cent improving to 6/5 by 15 days post op. Comparison of contrast sensitivity and aberrations pre-operatively and at three months showed an insignificant decrease and increase respectively. There were no reports of pain intra-op or post-op, no significant glare or haze, no complaints of dryness and no flap complications during or after surgery”.

Dr. Ganesh concluded “the flapless SMILE procedure makes minimally invasive refractive correction possible. SMILE produces excellent results, even in the case of high refractive errors.”

Comparing Vision Outcomes

In a prospective, randomised study comparing SMILE and femto LASIK in 100 eyes of 50 patients, pre-operative manifest refraction in the LASIK group was SE -3.88±2.23D and in the SMILE group was SE -5.47±2.21D. Dr. Ganesh also noted:

• UCVA at three months was 6/6 or better in 88 per cent of LASIK eyes and 96 per cent of SMILE eyes, with four and 12 per cent achieving 6/5 respectively.
• Post-operative higher order aberration was significantly higher in LASIK (0.437 ± 0.103µ) than SMILE (0.267 ± 0.07 µ; P < .001);
• Postoperative dry eye and glare were significantly more common following LASIK (P < .001).

He concluded refractive accuracy, dry eye, contrast, and induced aberrations are better following SMILE rather than LASIK.

…the flapless SMILE procedure makes minimally invasive refractive correction possible…

Optimising SMILE Surgery

Preferred treatment protocols, surgical instruments, parameters and techniques were reviewed:

Lenticule depth
With stronger anterior layers of the cornea remaining intact, traditional limits of residual stromal thickness compared with percentage tissue removal were discussed. The trend is to use a 120µ-135µ cap.

Enhancement options
Not all surgeons had completed SMILE enhancements, but the majority stated they would prefer PRK due to patient preference away from flap surgery, and safety. A new option was reviewed, converting the SMILE cap into a flap (creating a ‘CIRCLE’ side cut) and performing LASIK. This provides a good option, but a less invasive option is desired.

Optimising Results
Dr. Ganesh shared his recommendations. “In my experience, first day postoperative visual recovery is influenced by the bubble pattern, ease of dissection and time taken for dissection.” He highlighted the importance of overall fluence (laser energy) to optimise these factors.

To enhance visual results, he recommended surgeons use personalised nomogram adjustment for spherical and astigmatism correction; centre treatment on the Coaxial Sighted Corneal Light Reflex, and consider the patient’s head position. For patients with astigmatism, compensate for cyclotorsion by marking the cornea and rotating the interface before treatment.

Dr. Ganesh concluded that SMILE may offer a paradigm shift in the way refractive surgery is performed having all the advantages of LASIK and safety of PRK with the greatest patient comfort.

Katherine Napier is the Business Development Manager – Refractive Lasers within the Medical Business Group at Carl Zeiss.