Ablation Resolution in Laser Corneal Refractive Surgery : The Dual Fluence Concept of the AMARIS Platform

Abstract EN

Purpose.

To evaluate to which extent individual Zernike terms can be corrected.

Methods.

Ablation time and fidelity was analysed using different fluence levels (range 90–2000 mJ/cm2) and aspheric ablation profiles.

With optimal parameters, the extent to which individual Zernike modes can be corrected was evaluated.

Results.

The range 188–565 mJ/cm2 resulted as optimum fluence level with an optimum proportion range 50%–90% for high fluence.

With optimal parameters, it corresponds to 2.4 s/D at 6 mm OZ, with fidelity variance of 53 μm RMS, and average ablation error of 0.5 μm for each location.

Ablation simulation of coma Z[3,±1] showed 98,4% accuracy and 98% fit quality; trefoil Z[3,±3], 99,9% accuracy and 98% fit quality; spherical aberration Z[4,0], 96,6% accuracy and 97% fit quality; secondary astigmatism Z[4,±2], 97,9% accuracy and 98% fit quality.

Real ablation on a flat plate of PMMA of coma Z[3,±1] showed 96,7% accuracy and 96% fit quality; trefoil Z[3,±3], 97,1% accuracy and 96% fit quality; spherical aberration Z[4,0], with 93,9% accuracy and 90% fit quality; secondary astigmatism Z[4,±2], with 96,0% accuracy and 96% fit quality.

Conclusions.

Ablation of aspherical and customised shapes based upon Zernike polynomials up to the the 8th order seems accurate using the dual fluence concept implemented at the AMARIS platform.