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Ultrasound energy minimized with femtosecond MICS technique

MICS is more efficient than coaxial phacoemulsification because of its reliance on high vacuum, balanced fluidics with minimal ultrasound.

Issue: March 2014

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Femtosecond laser-assisted bimanual microincision cataract surgery required markedly less ultrasound power and phacoemulsification time than coaxial phacoemulsification, according to a study.

Surgically and statistically, MICS proved to be slightly more efficient than the coaxial method, the study authors said.

“Femtosecond laser-assisted microincision cataract surgery was the most efficient technique in terms of total phaco power and effective phaco time,” Jorge L. Alió, MD, PhD, an OSN Europe Edition Board Member and the corresponding author, said in an email interview with Ocular Surgery News. “This demonstrates, again, that minimizing the incision maximizes the outcomes of refractive surgery. This also proves that femtosecond-assisted surgery is relevant when everything is really taken to the limits in terms of minimal invasiveness and safety.”

The study was published in the Journal of Refractive Surgery.

Jorge L. Alió

Patients and procedures

The prospective, randomized study included 25 patients who underwent bimanual MICS with two 1-mm incisions and 25 patients who underwent coaxial phacoemulsification with a 1-mm paracentesis and 2.2-mm principal incision.

Excluded from the study were patients with nuclear cataracts of grade 2 or higher, previous refractive corneal surgery, corneal pathology, subluxated lens or weak zonules, pupillary dilatation failure, history of uveitis or retinal detach­ment surgery, or ocular or neurological diseases that might affect visual acuity or surgery.

The LenSx femtosecond laser (Alcon) was used to create incisions, perform capsulotomies and fragment lenses in all cases.

The primary outcome measures were ultrasound power, effective phacoemulsification time, postoperative spherical equivalent, corneal and internal higher-order aberrations, corneal thickness, endothelial cell count, macular thickness and complications at 1 month postoperatively.

Outcomes and observations

Mean postoperative uncorrected distance visual acuity at 1 month was 0.27 in the MICS group and 0.26 in the coaxial group. Mean postoperative corrected distance visual acuity was 0.20 in the MICS group and 0.15 in the coaxial group.

Mean postoperative spherical equivalent was –0.26 in the MICS group and –0.33 in the coaxial group.

Mean ultrasound power was 1.8% in the MICS group and 14.7% in the coaxial group; the between-group difference was statistically significant (P < .001).

“MICS is totally different, and the use of fluidics is more prevalent than phaco power, and softening of the nucleus is obviously benefiting from this,” Alió said.

Mean effective phacoemulsification time was 1.5 seconds in the MICS group and 4.5 seconds in the coaxial group (P = .002).

The efficacy index at 1 month was 160.2% for MICS and 149% for coaxial phacoemulsification.

“The main reason for femtosecond MICS to be more efficient is that it is a technique based on the use of fluidics,” Alió said. “Rather than power, femtosecond MICS is based on the use of high vacuum and balanced fluidics with minimal use of ultrasound.”

Both groups had similar corneal thicknesses, endothelial cell counts, macular thicknesses and complications.

“We did not suffer any complication in this series, neither in the standard nor in the MICS groups,” Alió said. “In experienced hands, once you undertake the adequate transition toward microincision surgery, knowing your parameters according to the phaco pump that you use and using the adequate instruments, you should not have any more differences between standard and MICS.”

Further study with a larger patient group and longer follow-up is needed to justify the cost of femtosecond laser tech­nology, the authors said. – by Matt Hasson

• Reference:
• Alió JL, et al. J Refract Surg. 2014;doi:10.3928/1081597X-20131217-04.
• For more information:
• Jorge L. Alió, MD, PhD, can be reached at Vissum, Instituto Oftalmologico de Alicante, Avda. de Denia, s/n, 03016 Alicante, Spain; 34-965-150-025; email: jlalio@vissum.com.

Disclosure: Alió has no relevant financial disclosures.