Custom LASIK Eye Surgery

Wavefront Optimization

The Allegretto affords clients with superior treatment, and one of the most innovative aspects of the Allegretto is the way in which it integrates wavefront optimization in the procedure. Representing a new generation of refractive technology, the Allegretto is the only vision-correction laser system whose holistic approach accounts for factors such as pupil position and tracking (the eyes will shift slightly due to our heartbeat, breathing, and microscopic visual tracking movements, called fast saccades), and the cornea’s initial curvature radius. Because it is specifically designed both to account for fast saccades and to preserve the natural curvature characteristics of the cornea, the wavefront optimization procedure is able to optimize visual quality, including the correction of higher order aberrations like halos, poor night vision, and glare.

While able to provide excellent results in treating lower order aberrations like nearsightedness, farsightedness and astigmatism , traditional surgery (much like wearing glasses and contacts), cannot treat higher order aberrations. Earlier vision-correction systems are tested on, calibrated, and designed for flat surfaces. These systems focus treatment area (the optical zone) on the front-center of the curved cornea, a very limited area. Thus, when treating the down-slope of the curved surface of the cornea, some laser energy scatters rather than being absorbed by the target tissue, resulting in a flattened circular area on the front-center of the cornea that ends with an abrupt edge. This break in the continuity of the cornea’s curvature is known as the cosine offset correction problem, as the amount of scattered energy is proportional to the cosine of the tangent at the point of laser contact. The result is unwanted side-effects like halos and other higher aberrations. This effect becomes more severe the more peripheral the laser aims from "straight down".

Imagine a glass ball. If a flashlight aimed directly at the top of the ball, the light would form a circular shape on the surface of the ball. If the flashlight now aimed towards the side of the ball, on the down-slope, the light would form an elliptical shape and not seem as bright anymore. This is because the same amount of light is distributed over a larger area, and some of the light is reflected away due to the angled surface.

Newer vision-correction procedures incorporate treatment patterns (called algorithms) that apply peripheral treatment in a blend zone around the optical zone. Specifically, the Allegretto system applies extra laser pulses to the peripheral cornea, enabling compensation for the angle of the laser beam. In an exceptionally holistic technique, the laser anticipates and counterbalances any cosine offset issues, thus preserving the naturally aspheric shape of the cornea to an unprecedented degree. The compensation of the extra pulses, along with the precision of the PerfectPulseTechnology™ (that enhances tissue sculpting accuracy with its meticulous calibration of the amount of energy in each laser pulse), produces a smoothly sculpted optical surface.

The Allegretto system is unrivaled in its consideration for and preservation of the eye’s natural curvature with its cosine-offset features and the aspheric treatment design for retaining optimum corneal geometry. Combined with the high speed pupil tracking techniques with the PerfectPulseTechnology™ (that will automatically pause the treatment and wait until the eye is back in position, should the eye ever move too fast or out of range of the tracking system during treatment), the Allegretto wavefront optimization substantiates the achievement of “high performance vision.”