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P. Vinciguerra, D. Epstein; A Comparison of Two Excimer Laser Custom Ablation Platforms. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5322.
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© ARVO (1962-2015); The Authors (2016-present)
To compare two excimer laser custom ablation platforms, one based on topography and a spherical algorithm, one on the total wavefront (WF) and an aspheric algorithm.
The custom ablation transition zone (CATZ) and the optical path difference (OPD), both Nidek platforms, were compared. CATZ, based on topography (or corneal WF) and a spherical algorithm (OZ 6.5 mm, TZ 10.0 mm) was performed on 158 eyes with a mean preoperative spherical equivalent (SE) refraction of -3.64D±3.78D (range, +5.75D to -12.50D). OPD, based on the total WF and an aspheric algorithm (OZ 6.0 mm, TZ 10.0 mm) was performed on 68 eyes with a mean preoperative SE 0f -5.67D±2.03D (range, -2.50D to -11.25D). Mean ages were 37 and 34 years, respectively. Both custom platforms enable the surgeon to simulate the postoperative shape of the cornea in the form of a topographic or WF map. Also, in both platforms it is possible to select or exclude any single order or component of the Zernike pyramid up to the 8th order. All procedures were done as surface ablations. Minimum follow-up was 12 months in both groups.
At 12 months, the CATZ eyes had a mean SE of +0.05D±0.96D, the OPD eyes a mean of 0.00D±0.63D, with excellent refractive stability throughout the first postoperative year for both groups. No eye lost 2 or more lines of BSCVA in either cohort. In the CATZ group, 73% of the eyes were within 0.50D of aim at 12 months, in the OPD group 65%. Both platforms were effective in reducing higher-order aberrations, with OPD somewhat more effective in reducing spherical aberration, especially in 5-mm pupils.
Excellent outcomes were obtained with both custom ablation platforms. All other parameters being equal, the choice of one or the other platform may come down to which algorithm saves more tissue in a given eye. CATZ has shown itself especially useful in retreatments, because the surgeon can predetermine a given postoperative curvature and diameter in the center of the cornea. OPD can correct both corneal and internal aberrations.
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