COMMENTARY

Femtosecond Laser Cataract Surgery: Conquering the Learning Curve

William W. Culbertson, MD

Disclosures

July 20, 2012

Early Experience With the Femtosecond Laser for Cataract Surgery

Bali SJ, Hodge C, Lawless M, Roberts TV, Sutton G
Ophthalmology. 2012;119;891-899

Going Beyond LASIK

Since its introduction in ophthalmic surgery 10 years ago, the femtosecond laser has demonstrated its utility for improving the predictability, precision, and safety of corneal surgery, primarily in making the corneal flap for LASIK surgery.[1,2] The laser-created flap's superiority over flaps made manually with a blade microkeratome has resulted in the gradual supplanting of the manual blade microkeratome by the more automated software-driven "femtosecond laser microkeratome," in spite of its comparatively increased time and cost.

In contrast to its success in LASIK flap making, the femtosecond laser has been slow to be adopted for other corneal applications, such as for keratoplasty and refractive keratotomy, even though it clearly makes more precise incisions compared with the manual incisions made with a blade.[3,4] This difference in adoption rates is probably related to the fact that clearly superior visual outcomes have not yet been reported and surgeons are reluctant to incur the extra time and unreimbursed expense in using the laser for these non-LASIK corneal procedures.

More recently, the femtosecond laser has been adapted for use in cataract surgery with the hope that its precise photodisruptive energy could be harnessed and focused to make cataract surgery safer with more predictable optical outcomes.[5,6] Close to real-time imaging of the dimensions of the anterior segment of the eye (such as with optical coherence tomography) has been required to precisely focus the laser in the intended target tissues, such as the cornea, anterior lens capsule, and the nucleus of the cataract.[7]

Initial clinical studies with small groups of patients have shown that the critical anterior capsulotomy parameters of size, shape, and position could be precisely and predictably created with the femtosecond laser cataract surgery instruments. Preliminary reports at national and international meetings have indicated that the intended postoperative refractive target has been more accurate in femtosecond laser capsulotomy cases as compared with manual capsulotomy cases, possibly because of a more predictable effective lens position in laser cases.[8]

Laboratory investigation has demonstrated increased resistance of the laser-created anterior capsulotomy edge to tearing forces, suggesting that intraoperative capsulotomy tears should theoretically be reduced in frequency compared with the rate of tears with relatively weaker-edged manual capsulotomies. In addition, femtosecond laser presegmentation and presoftening ("femtoemulsification") of the nucleus of the cataract has resulted in markedly reduced intraocular maneuvers and even eliminated phacoemulsification energy use in the aspiration of the cataract nucleus.

Study Summary

Bali and colleagues reported their experience with their first 200 eyes undergoing cataract surgery assisted by the LenSx® (Alcon®; Fort Worth, Texas) femtosecond laser. Six surgeons performed surgeries at one center, and they examined the incidence of complications and undesirable events in 4 sequential 50-eye groups and compared them with a corresponding traditional manual surgery control group of 1000 cases. The investigators did not report on the visual outcomes of either group and implied that they would be addressed in a subsequent publication.

In general, they found a significantly higher rate of intraoperative problems in the femtosecond laser group than in the traditional manual group. In the laser-treated group, only 17.5% had free-floating complete anterior capsules, 4% of eyes had anterior capsular tears, 3.5% had posterior capsule breaks, and 4 eyes (2%) had loss of the nucleus into the vitreous cavity. The occurrence of these undesirable events was significantly more frequent than in the control group. The investigators speculated that unrecognized incomplete anterior capsulotomy incisions may have led to propagation of a tear peripherally during the manual removal of the capsule cap. In 4 cases, the lens nucleus was lost into the vitreous cavity during surgery because of an opening in the posterior capsule. They attributed these events to unintended overfilling of the capsular bag with balanced salt solution during hydrodissection and consequent bursting of the capsular bag in 2 cases and to extension of anterior radial tears in the other 2 cases.

They also experienced difficulty docking the LenSx 1-piece curved contact lens to the patient's eye, requiring 1.5 attempts per patient, on average, to achieve coupling. This ratio improved with increasing docking experience.

The laser-assisted surgery also required more time than standard surgery because of the extra step in maneuvering and mating the patient to the laser, performing the laser treatment, and then bringing the patient to the surgical suite. The time in the operating room after laser pretreatment was also surprisingly longer, 19.8 minutes in the early cases compared with 15.7 minutes for the control cases, although this time decreased to 18.3 minutes as more experience was gained in successive cases. It is expected that surgery time with laser cases will ultimately be shorter than with conventional cases as some of the technical and procedural delays are reconciled.

Viewpoint

The incidence of complications and problems in this study declined with each 50-eye group as the surgeons gained more experience operating the laser. This type of learning curve is anticipated with every new surgical technique and is progressively optimized for efficiency and avoidance of adverse events as experience is gained. Improved functionality of the laser instrument is also expected as various shortcomings of the individual machines become apparent and engineering designs are modified.

With any new technology, there is a learning curve both for the surgeons using the instruments and for the companies manufacturing them.[9] Unanticipated technical problems, such as a suboptimal contact cone causing posterior corneal folds with inadequate laser focusing, could lead to incomplete anterior capsulotomies with the sequelae reported in this study. Similarly, inadequate imaging could lead to unintended lasing of the posterior capsule and an inadvertent posterior capsule break.

Bali and colleagues are to be commended for this published report of their early experience with femtosecond laser-assisted cataract surgery. As a result of their reported experience and observations, surgeons will be able to shorten their learning curves, and, we hope, the instrument companies will address the technical challenges made apparent in this study. We anticipate that just as improvements in instrumentation and technique improved outcomes and reduced the incidence of complications for early iterations of phacoemulsification surgery, femtosecond laser-facilitated cataract surgery will work out its early inconsistencies.[10,11]

Abstract

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