Technology requirements for Summit-Autonomous CustomCornea.

W ith the recent surge of interest in wave-front sensing technology as a new diagnostic tool in refractive surgery 1,2 , the concept of wavefront customized correction has now come to the forefront. 3,4 Among the companies leading this effort, the Summit-Autonomous Technologies provides a technology platform within CustomCornea which can be used as a model for wavefront ablation requirements. Although the technology requirements for wave-front guided ablation are unique to a given laser and wavefront sensing device, the essential components can be summarized in part by using the example provided by a specific company and a specific technology platform, namely CustomCornea. Spot Size and Shape Although many of today's commercially available excimer laser systems have beam diameters which vary in size and profile shape, it is the small scanning spot of guassian shape that is the essential first requirement for wavefront customized abla-tion. A gaussian beam allows for very uniform overlap in the creation of a smooth customized ablation profile. This is in contrast to a top-hat beam created by concentric iris apertures, which produce sharp abla-tion edges that may overlap in the laser vision correction profile. Additionally, the size of the spot must correspond to the resolution of aberrations being treated. Mathematical calculation of the spot ize required to correct fourth order aberrations within an optical ablation zone diameter of 6 mm require a spot size of р1 mm (unpublished data). Therefore, scanning spot lasers larger than 1 mm would not adequately treat the most common of higher order aberrations, namely spherical aberration and coma. In a study of small spot scanning, a 2 mm top-hat beam profile results in performance degradation of both low and high spatial frequency during custom ablation. 5 This is in contrast to a 1 mm gaussian beam, which shows good performance when treating both high and low spatial frequency aberrations. 5 The Summit-Autonomous LADARVision laser uses a 0.8 mm gaussian spot during both its conventional and CustomCornea ablations. Spot Scanning Rate The majority of the small spot gaussian profile lasers use a spot scanning rate of approximately 200 Hz. The Summit Autonomous LADARVision laser, however, uses a spot scanning rate of only 60 Hz. Even though the spot frequency for the LADARVision system is considerably slower than the other small spot scanning lasers, the actual ablation time is shorter with the LADARVision (8 seconds per diopter) than when using the LaserSight LSX …