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Maria Vinas, Carlos Dorronsoro, Lucie Sawides, Daniel Cortés, Daniel Pascual, Aiswaryah Radhakrishnan, Susana Marcos; Longitudinal Chromatic Aberration of the human eye in the visible and near infrared from Hartmann-Shack wavefront sensing, double-pass and psychophysics. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5974.
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© ARVO (1962-2015); The Authors (2016-present)
Longitudinal Chromatic Aberration (LCA) plays an important role on polychromatic optical quality and retinal imaging at different wavelengths (λ). However, the reported LCA varies across studies, likely associated to the different measurement techniques. We present LCA obtained from Hartmann-Shack (HS) wavefront sensing, double-pass (DP), and psychophysical methods in the same subjects.
A supercontinuum laser (450-1020nm) was used as the light source in custom-develop Adaptive Optics (AO) system provided with a HS (HASO, Imagine Eyes) and a deformable mirror (MIRAO, Imagine Eyes) to measure and correct the aberrations of the system and/or eye. The system incorporates a motorized Badal system, a natural pupil monitoring system, a CCD camera capturing aerial retinal images, and a psychophysical channel with monochromatically back-illuminated stimuli. A total of 16 wavelengths were tested using 2 fiber-optic-channels: 450-650nm in the visible (VIS), and 700-1020nm in the near infrared (NIR). Measurements were performed on 5 subjects (35.60±3.3yrs; -2.75±1.9D) with dilated pupils (6-mm artificial pupil). LCA was estimated from measurements at all λ from: (1) the defocus Zernike terms from HS wave aberrations; (2) best focused images of through-focus (0.25D steps) DP aerial image series; (3) subjective Badal best focusing of monochromatic stimuli (VIS only). Measurements were corrected by the calibrated LCA of the optical system (0.05D in VIS/0.28D in NIR).
The average VIS LCA (488-650nm) was 0.83±0.18D from HS, 0.84±0.08D from DP, and 1.16±0.03D (1.56 ± 0.03 D for 450-650nm) from subjective best focus. The average NIR LCA (650-950nm) was 0.39±0.18D from HS and 0.33±0.10D from DP. The average Total VIS-NIR LCA (488-950nm) was 1.30±0.23D from HS and 1.54±0.23D from DP.
A custom-made polychromatic AO system allowed objective and subjective measurements of LCA, in a wider range (HS and DP) than previously explored. Subjective LCA (best focus, large pupils) is significantly higher than LCA from reflectometric techniques (HS and DP, both in excellent agreement). LCA measurements under AO-corrected aberrations with this system will give insights on the origin of the systematic discrepancies of subjective/objective LCA: presence of aberrations or λ-dependency of the retinal reflective layer.
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