Since the introduction of ultrasound phacoemulsification in 1967, cataract surgery has become the most commonly performed outpatient operation in the US. While phacoemulsification has been shown safe and effective, application of ultrasound power within the eye does carry some risk of ocular injury, such as endothelial cell loss. In addition, the manual method of creating the anterior capsulotomy, which is performed using the continuous curvilinear capsulorhexis (CCC), cannot ensure that the capsulotomy is consistently centred or circular,1–3 thereby affecting the effective lens position (ELP). This is especially significant for multifocal, accommodating and toric intraocular lenses (IOLs) with more complex optical designs.
Recently, there has been increasing interest in the use of femtosecond lasers as an adjunct to ultrasound phacoemulsification in cataract surgery. Clinical studies have demonstrated incremental improvements with femtosecond laser-assisted cataract surgery compared with standard ultrasound.4 Femtosecond lasers deliver ultrashort pulses of infrared energy so that collateral tissue damage is avoided. They cut tissue by photodisruption, that is, vapourisation of targeted tissue, generation of cavitation bubbles and creation of cleavage planes within tissue.5 As transparent tissues do not absorb the lasers’ infrared wavelengths, photodisruption can be focused precisely at a given depth within the anterior segment of the eye.
Four femtosecond laser systems have been cleared by the US Food and Drug Administration (FDA) for capsulotomy, phacofragmentation and construction of corneal incisions in the context of cataract surgery: LenSx® (Alcon, Fort Worth, Texas), Catalys® (Abbott Medical Optics, Santa Ana, California), LENSAR® (LENSAR, Orlando, Florida) and Victus® (Bausch & Lomb, Rochester, New York). This article discusses the technological specifications and clinical applications of the LENSAR Laser System.
Specifications and Performance
The LENSAR Laser System was designed from the beginning to meet the strictest standards of accuracy and precision specifically for refractive cataract surgery. Optimal docking, imaging and guidance set the stage for accurate laser shot placement and effective cutting, making the LENSAR Laser System the perfect preparation for phaco aspiration, IOL implantation and wound sealing. The intrinsic qualities of LENSAR’s optical laser, coupled with its novel, patented proprietary imaging technology and user-friendly patient interface, provide predictable and reproducible results, including free-floating anterior capsulotomies, ultrasound-sparing phacofragmentation patterns, easily opened clear corneal incisions (CCIs) and precise arcuate cuts. The outstanding safety and effectiveness of these advanced algorithms drive enhanced outcomes and improved satisfaction for all IOL patients. In addition, the capability for integration of preoperative imaging and intraoperative guidance through iris registration allows increased efficiency and accuracy of arcuate incisions. Finally, the intraoperative ability to define the cataract nuclear density facilitates optimal phacofragmentation.
The unique utility and superior efficiency of the LENSAR Laser System-fs 3D (LLS-fs 3D) Augmented Reality™ result from these major innovations:
- Ergonomic profile and flexible system footprint that function efficiently in any operating environment.
- Patient-friendly, low-pressure liquid interface that allows for comfort, stable fixation and ease of use.
- Augmented Reality structured scanning illumination and highresolution imaging that provides automated surface detection, including accurate tilt and curvature correction in all axes. Structured scanning illumination adjusts the intensity of illumination for each specific structure so that dim features appear brighter and bright features do not saturate. Structured scanning results in uniform image brightness from anterior cornea to posterior lens capsule ensuring robust image processing that improves the accuracy and reliability of automated surface detection.
- Proprietary intraoperative imaging of the cornea that insures accuracy is maintained while each incision is performed. This imaging process takes place just prior to construction of each corneal incision, allowing adjustment of incision location and depth in order to compensate for any movement that necessarily occurs as a result of capsulotomy, fragmentation or previous corneal incision construction.
- Precise laser delivery and placement that allows accurately structured multiplane corneal incisions, safe free-floating capsulotomies to within 250 μm of the pupil margin and safe phacofragmentation to within 500 μm of the posterior capsule.
- Planned addition of wireless data transmission of preoperative iris image capture and corneal biometry with pending addition of intraoperative iris registration that corrects for cyclotorsion in astigmatism treatment planning.
- Intraoperative cataract analysis that facilitates selection of phacofragmentation pattern for optimal reduction of energy.
The LLS-fs 3D was designed for maximum flexibility with cataract surgeons in mind. The laser may be installed within a preoperative treatment room, holding area or operating room (see Figure 1). It has a small footprint and is fully mobile. The laser can be moved away from the patient’s bed to allow for positioning of a surgical microscope and ultrasound phacoemulsification system, so the patient does not have to be transferred to another operating bed or moved to a separate room. It works with any rolling bed or rolling chair in the office, ambulatory surgery centre or hospital outpatient environment. The patient bed can be positioned in line with the laser or perpendicular to the laser to allow for maximum utilisation of the existing space.
The femtosecond procedure is surgeon controlled from a joystick and fully visualised on a dedicated surgeon’s monitor. The docking head is on an extending arm that is electronically deployed to a neutral position, ready to receive the patient. Placement of the patient interface device (PID) proceeds smoothly and comfortably. After the PID is applied, the laser head is docked to the interface via the patient interface arm, using a joystick. Fine calibration permits smooth, delicate docking. The docking head itself is under patented servo control and maintains a low predetermined force on the eye, minimising any impact on ocular tissues or intraocular pressure (IOP). Three screens provide viewing capability for the surgeon, circulating nurse and technician. The surgeon may sit in a superior or temporal position, and perform the entire procedure solo or with an assistant. Once imaging of the anterior segment and femtosecond laser treatment are complete, suction is automatically released and the docking head is retracted to an out-of-the-way neutral position. To allow greater working distance, the docking head can be programmed to automatically move back even further to allow additional unrestricted access to the patient.
The intuitive user interface on the monitor allows the surgeon to customise the treatment beyond default software parameters. Capsulotomy size can be programmed according to the IOL manufacturer’s recommended specifications or the surgeon’s preference. The width of the fragmentation pattern can be extended or reduced within the pupil diameter subject only to programmed safety margins. The depth of the pattern can be increased to fragment the posterior nuclear plate. Laser energy and spot density can be pre-programmed or adjusted based on the intraoperative ability to define cataract grading to insure effective phacofragmentation in both soft and dense cataracts.
In addition to the standard phacofragmentation patterns, the LLS-fs 3D provides full customisation options for femtosecond laser treatment. This customisation is available via the selection of a surgery profile. This profile can be completely customised by accessing the LENSAR pattern designer feature. The capsulotomy, phacofragmentation pattern and incisions can be customised for each individual patient or the optimised LENSAR patterns may be utilised. Fragmentation options include both cylindrical and cubic patterns, and adding one to four chops can provide additional phacofragmentation. More parameters can be accessed to provide complete control of the size and spacing of the selected pattern.