Comparison of Higher-Order Aberration Measurements From Hartmann-Shack Fourier-Based and Tscherning Zernike-Based Aberrometers in LASIK Patients
Narrative Responses:
Purpose
To assess the agreement of higher order aberration measurements from the VISX WaveScan and the Wavelight Allegro in LASIK patients.
Methods
Multiple readings were obtained pre-operatively and at post-operative month twelve in 100 eyes of 50 subjects undergoing LASIK with the VISX Wavescan and Wavelight Allegro aberrometers. The parameters of coma, trefoil, defocus, spherical aberration, and total higher order aberrations (HOAs) were compared using intraclass correlation coefficients (ICC), for which perfect agreement equals 1 and disagreement equals 0.
Results
Preoperative correlation was good between the aberrometers for the parameters of defocus, astigmatism, and spherical aberration (ICC: defocus=0.8, astigmatism=0.9, spherical aberration=0.7), but was poor for the parameters of coma, trefoil, and total HOAs (ICC: coma=0.6, trefoil=0.2, total HOAs=0.4). Post-operative month 12 correlations became worse for all parameters and were 0.5 or less with exception to defocus and spherical aberration (ICC: defocus=0.5, astigmatism=0.2, spherical aberration=0.6, coma=0.4, trefoil=-0.3, total HOAs=0.2).
Conclusion
Although some HOAs measured with the VISX Wavescan and Wavelight Allegro agree preoperatively, such agreement may degrade after LASIK. This could be due to variable effects of LASIK on the Hartmann-Shack (WaveScan) and Tscherning (Allegro) techniques for measuring wavefront aberrations as well as the Zernike (Allegro) and Fourier (WaveScan) polynomials.