Lenticule Extraction Gaining Fans
New lasers expand options and indications.
Cheryl Guttman Krader
Published: Thursday, February 1, 2024
The 2022 ESCRS Clinical Trends Survey showed only 12% of respondents use femtosecond intrastromal lenticule extraction as a treatment for patients interested in refractive surgery. Will the availability of a new femtosecond laser (ELITA), approval of the indication for two existing lasers (Z8 and ATOS), and the anticipated approval of an indication for treatment of hyperopia/hyperopic astigmatism using the VISUMAX 800 laser affect adoption rates?
New laser debut
According to Rohit Shetty MD, PhD, lenticule extraction performed using the new ELITA laser in a procedure dubbed “SILK” (Smooth Incision Lenticule Keratomileusis) is characterised by several unique features. First, the intrastromal lenticule has a novel biconvex shape. In addition, the procedure is unlikely to cause irregularity of Bowman’s membrane, and it has minimal effects on spherical aberration (SA), corneal epithelium, and corneal nerves.
“Together, these features address the needs of patients concerned about flap displacement, dry eye, speed of recovery, and quality of vision after LASIK,” Dr Shetty said.
He pointed out that achieving a smooth, wrinkle-free Bowman’s membrane is important for visual quality.
“Outcomes after lenticule extraction depend not only on the quality of the laser and the surgeon’s skill but also on its effects on the corneal tissue,” he said. “Bowman’s membrane irregularity after lenticule removal can result in irregular optics that can be a major cause of poor vision and patient dissatisfaction.”
Creating a biconvex-shaped lenticule profile, demonstrated via a 3.0 D reconstruction of anterior segment OCT maps, strongly impacts quality of vision because it accounts for minimal postoperative change in SA. In an analysis of 125 eyes treated with SILK, mean change in SA at 3 months postoperatively was just 0.02 microns.
“Minimal change in SA is associated with good depth perception and gives patients good night vision,” Dr Shetty said.
He added the procedure also has implications for good depth of focus, as evidenced by data showing the refractive and aberrometric status during accommodation in eyes undergoing SILK was close to that of emmetropic eyes.
Dr Shetty also proposed any impact on corneal nerves is minimised in the SILK procedure, perhaps because the ELITA laser operates at a low energy level and because of the lenticule’s unique shape. He reported corneal nerve regeneration occurs relatively quickly after the surgery.
“Better and faster nerve regeneration likely means less dry eye and better wound healing, resulting in a more regular corneal epithelium,” he said. “A better tear film and smoother corneal surface translate into better optical and visual outcomes.”
Expanding the indication
Data from an international multicentre registration trial demonstrating the efficacy and safety of SMILE for hyperopia/hyperopic astigmatism have been submitted to support CE mark receipt.1 With approval, this procedure will provide an excellent new option for laser vision correction, said Walter Sekundo MD, PhD.
The registration trial used the VisuMax laser to create lenticules. However, when the software for hyperopia and hyperopic astigmatism treatment is released, it will be available only for the next-generation VISUMAX 800.
Dr Sekundo explained that multiple modifications to the procedure improved the hyperopic lenticule extraction outcomes performed with the original VisuMax laser over time. However, the suction loss rate in the registration trial was unacceptably high at 1.34% and related to the treatment time of about 35 seconds.
“The solution to this problem is to use the VISUMAX 800. We showed a porcine eye model took 12 seconds to cut the hyperopic lenticule,” Dr Sekundo said.
“Since I began using the VISUMAX 800 in October 2021, I have not had a single case of suction loss during SMILE pro procedure.”
The VISUMAX 800 also offers cyclotorsion adjustment and a patented computer-assisted centration function, which addresses the heightened need for excellent centration in hyperopic treatments.
Summarising other results from the registration trial, Dr Sekundo reported that 69% of the 219 eyes targeted for plano distance achieved UCVA of 20/20 or better at 12 months. Only 1.2% of the 374 eyes in the total cohort lost two or more lines of corrected distance VA.
“I remind you that loss of corrected VA is more common with a hyperopic versus myopic laser treatment, and so these are excellent results,” Dr Sekundo said.
Some undercorrection was seen in the predictability analysis, and it was more significant in eyes treated for higher levels of hyperopia. The commercially released software will incorporate a nomogram adjustment based on this finding.
“Even so, the achieved refraction was within 0.5 D of intended in 81% of eyes, which is slightly better than LASIK and an excellent result for a hyperopic treatment,” Dr Sekundo said.
“Refractive stability was good overall. While there was some regression between 3 and 12 months, it unclear if the shift is the result of late epithelial healing or progression of presbyopia.”
Dr Shetty and Dr Sekundo spoke during the 2023 ESCRS Congress in Vienna.
For citation notes, see page 48.
Rohit Shetty MD, PhD is Chairman of Narayana Nethralaya Eye Institute, Bangalore, India. firstname.lastname@example.org
Walter Sekundo MD, PhD is Professor and Chair, Department of Ophthalmology, Philipps University of Marburg, Germany. email@example.com