How femtosecond laser-assisted cataract surgery helps in challenging cases

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Features of a proprietary femtosecond laser system enable successful laser-assisted cataract surgery in eyes with a history of LASIK or other pre-existing corneal conditions. The addition of intraoperative aberrometry optimizes IOL power selection.

By Cheryl Guttman Krader; Reviewed by Kerry K. Assil, MD

Beverly Hills, CA-While there are a growing number of reports describing benefits of femtosecond laser-assisted cataract surgery (FLACS) for improving surgical safety and refractive outcomes, there is a lack of information about use of the technique in eyes with a history of LASIK.

According to research presented by Kerry K. Assil, MD, FLACS can be performed safely and effectively in postLASIK eyes, at least using a particular femtosecond laser platform (LensAR Laser System, LensAR), and the addition of intraoperative aberrometry (ORA System with VerifEye, WaveTec Vision) may contribute to more accurate refractive outcomes for this challenging cohort.

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“Concerns have been raised about docking, imaging, and treatment with the femtosecond laser in eyes with a history of LASIK or other pre-existing corneal conditions,” said Dr. Assil, medical director, The Assil Eye Institute, Beverly Hills, CA.

“However, because of its efficient and simple docking, superior imaging system, and precise laser spot delivery capability, the LensAR femtosecond laser provides surgeons with a user-friendly system for achieving accurate laser augmented cataract surgery, even in the presence of corneal comorbidities,” he said. “Based on my experience, I consider it the system most capable of transforming cataract surgery.”

Dr. Assil presented results from up to 3 months of follow-up for 66 eyes of 49 patients. All eyes had capsulotomy and lens fragmentation performed with the LensAR laser. Confirmation of aphakic refraction with refinement of IOL power selection as needed was performed with the WaveTec intraoperative aberrometry platform. Twenty-nine of the patients had a history of LASIK, and a number of patients had other corneal conditions, including prior radial keratotomy, anterior lamellar keratoplasty, steep keratometry, and Fuchs dystrophy.

Mean distance UCVA in the total cohort was better than 20/30 at 1 month after surgery and had improved further at 3 months. The functional results were even better in the postLASIK subgroup, Dr. Assil noted.

Analyses of refractive outcomes for the total cohort and postLASIK subgroup showed very tight correlation between the achieved and intended spherical equivalent at both follow-up visits (R value range, 0.91 to 0.97). Dr. Assil stated that in his hands, the LensAR femtosecond laser augmented the safety net, while the WaveTec aberrometer enhanced the refractive target outcomes by better pinpointing of the residual astigmatism and prediction of the desired IOL power.

Discussing some of the assets of the LensAR system, Dr. Assil explained that the fluid-filled patient interface eliminates striae that can develop with contact applanation systems. The fluid interface also reduces the required degree of suction ring vacuum, thus minimizing conjunctival disturbance, as well as reducing IOP elevation. The system also has an internal closed loop vacuum sensor, further minimizing any suction breaks. With its joystick control, the low-pressure docking system is also fast and easy to use.

The absence of direct corneal applanation also enhances laser performance in performing peri-limbal arcuate corneal incisions, thus not interfering with the performance of intraoperative aberrometry. A more important consequence of placing the corneal incisions closer to the limbus using this particular laser system is the diminished likelihood for future corneal ectasia.

Compared with the OCT-based imaging technologies (found on other femtosecond lasers), the proprietary system of the Lensar laser (Augmented Reality) also stands out, according to Dr. Assil.

Designed to meet the specific needs of imaging widely varying degrees of encountered media opacities within the eye, the LensAR technology provides exquisitely discriminating surface detection and tissue penetrating illumination, enabled by its variable rate scanning coupled with infrared confocal illumination. These technologies are merged along with high definition, 10 distinct angle Scheimpflug imaging, movement detection, and culminated with ray tracing 3-D visual augmentation algorithms. The high-resolution resultant image quality supports fully automated processing to precisely locate the anterior and posterior corneal and lens surfaces (irrespective of the degree of nuclear sclerosis) for safe, accurate and reproducible treatment.

“On occasion, the laser’s imaging capability has also uncovered novel patient specific anatomical anomalies, such as stretched zonules or posterior capsular defects, and thus enabled the surgeon to modify surgical technique in order to optimize patient outcomes,” Dr. Assil said.

“The high-contrast imaging can allow for proper pinpoint identification of the posterior capsule even in an eye with a retracted and prominent anterior hyaloid face or one with a dense nucleus and posterior polar cataract, thus alerting the surgeon to consider adjustments in laser spot delivery, phacoemulsification technique or bottle height settings, to avoid what might have previously been considered an ‘unavoidable’ posterior capsule rupture,” Dr. Assil said.

Compared with other currently available femtosecond laser systems, the LensAR laser also has the most precise parallax resolving, imaging system (due to its imaging from 10 distinct angles), thus overcoming the illusion of “lens tilt.” This feature assures the anterior capsulotomy will be accurately centered and 100% complete, free of capsular tags or radial tears.

More importantly, the system enables highly efficient nuclear fragmentation, yielding "free floating" nuclear fragments and in the presence of minimal gas formation, thus making the phacoemulsification simpler and safer, without inducing sticky cortex.

Kerry K. Assil, MD

E: kerry2020@gmail.com

This article was adapted from Dr. Assil’s presentation during the 2014 meeting of the American Society of Cataract and Refractive Surgery. Dr. Assil is a paid consultant to LensAR, WaveTec, and other companies manufacturing technology used in cataract surgery.