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Corneal higher-order aberrations measurements: Comparison between Scheimpflug and dual Scheimpflug-Placido technology
Andre L Piccinini1, Oren Golan2, Emilio A Torres-Netto3
1Keck School of Medicine of the University of Southern California, Los Angeles, California, USA; Sadalla Amin Ghanem Eye Hospital, Joinville, SC, Brazil.
Purpose:
To compare the difference and agreement of corneal higher-order aberrations (HOAs) in keratoconic eyes using Scheimpflug and dual Scheimpflug-Placido imaging systems.
Setting:
Emory University, Atlanta, Georgia, and the University of Southern California, Los Angeles, California, USA.
Design:
Retrospective between-devices reliability and agreement study.
Methods:
Patients diagnosed with keratoconus were evaluated sequentially by Scheimpflug and dual Scheimpflug-Placido devices. Differences, correlations, and agreement between values for total root mean square (RMS), trefoil, coma, and spherical aberration were analyzed, and Bland-Altman plots were generated.
Results:
Fifty eyes from 50 patients (31 men, 19 women) were evaluated. Trefoil at 30 degrees, spherical aberration, and total RMS were significantly different between groups (P < .05), whereas trefoil at 0 degrees and total coma values were not statistically different. There was a weak positive correlation between devices for trefoil at 0 degrees (r = 0.228), and a moderate positive correlation for trefoil at 30 degrees (r = 0.473), horizontal coma (r = 0.430), and for total corneal RMS (r = 0.637). Vertical coma (r = 0.816) and spherical aberration (r = 0.874) showed a strong positive correlation. The 95% limits of agreement (LoA) for absolute values were 1.963 μm for trefoil at 30 degrees, 2.449 μm for trefoil at 0 degrees, 3.530 μm for horizontal coma, 2.145 μm for vertical coma, 1.242 μm for spherical aberration, and 10.527 μm for RMS.
Conclusion:
Significant differences were found between measurements of corneal HOAs generated by Scheimpflug and dual Scheimpflug-Placido devices in patients with keratoconus, with generally limited correlations and wide LoA. HOAs measurements from these devices should not be considered equivalent.
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