WaveLight Allegretto Wave Eye-Q Laser
Vanee Virasch
Jonathan B. Rubenstein
The WaveLight Allegretto Wave Eye-Q Laser can be used for Wavefront Optimized LASIK treatments and, in conjunction with the WaveLight Analyzer, for wavefront-guided Custom LASIK treatments.
This platform is a scanning flying spot excimer laser that exists at three frequencies, 200, 400, and 500 Hz, with a pulse duration of 12 ns. The ablation times are very rapid with the 200-Hz laser correcting 1 diopter (D) at a 6.5-mm optical zone in about 4 seconds, while the 400-Hz laser can correct 1 D in only 2 seconds. The scanning spot laser overlaps a previous ablation spot every fifth pulse, allowing cooling time between pulse applications and decreasing any theoretical thermal risk.
The system is equipped with an integrated cross-line projector that allows not only horizontal centration, but also vertical, or z-axis, centration on the cornea. Correct height alignment is achieved with two precise distance laser diodes. This is an advantage particularly in patients requiring high astigmatic correction. The laser’s PerfectPulse Technology utilizes a Gaussian beam profile and a 0.95-mm spot size to ensure a smooth and precise ablation of corneal tissue. This is coupled with a highspeed eye-tracking system with a response time of <6 ms for accurate placement of each laser pulse. The pupil-based eye-tracking system can be used with a pupil size ranging from 1.5 to 8.0 mm and does not require pupil dilation. A built-in slit lamp is also provided, which allows the surgeon to inspect both flap alignment and interface clarity while the patient is on the operating table. It can also be used to find the flap edge in a retreat case. Other features of this laser include a bright 110W xenon illumination system and a portable notebook computer that allows the surgeon to program the laser treatments, preoperatively from a separate location. There is an external plume evacuator that removes fumes and odors from the surgical field, thus protecting both the patient and surgeon. The laser is attached to a motorized swiveling bed that also moves the patient under the laser with push button control. The laser is also less sensitive to changes in temperature and humidity, because the optics of the beam formation is protected inside a tube system that is nitrogen gas purged. Only a very short part of the excimer laser beam is exposed to ambient air. The overall fluence is measured by objective calibration and adjusted for the individual room conditions once a day. Temperature and humidity in the laser room should still be controlled in order to manage the response of the patient’s cornea. The laser is able to operate at temperatures that range from 65°F to 86°F and 20% to 70% relative humidity.
▪ Wavefront Optimized LASIK
The objective of Wavefront Optimized technology is to preserve the natural asphericity of the cornea. Previous LASIK platforms resulted in non-aspheric ablation profiles, flattening the central cornea more than the peripheral cornea and inducing spherical aberration. These ablation profiles also resulted in larger and more irregular transition zones.
Wavefront Optimized treatment is a novel technology that improves upon previous
ablation profiles by altering the way in which the peripheral cornea is ablated. Due to the angle of incidence of the laser beam, there is increased reflection and energy loss as the treatment beam moves peripherally along the curved cornea. Therefore, with a nonoptimized ablation profile, less energy is delivered to the peripheral cornea, which results in a non-aspheric corneal surface. In order to compensate for this, the Wavefront Optimized laser creates an ablation profile that places more laser pulses in the peripheral zone depending upon each individual’s degree of corneal steepness (Figs. 8.1A and B
ablation profiles by altering the way in which the peripheral cornea is ablated. Due to the angle of incidence of the laser beam, there is increased reflection and energy loss as the treatment beam moves peripherally along the curved cornea. Therefore, with a nonoptimized ablation profile, less energy is delivered to the peripheral cornea, which results in a non-aspheric corneal surface. In order to compensate for this, the Wavefront Optimized laser creates an ablation profile that places more laser pulses in the peripheral zone depending upon each individual’s degree of corneal steepness (Figs. 8.1A and B