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Forward light scatter analysis of the eye in a spatially-resolved double-pass optical system.

Nam J, Thibos LN, Bradley A, Himebaugh N, Liu H - Opt Express (2011)

Bottom Line: An optical analysis is developed to separate forward light scatter of the human eye from the conventional wavefront aberrations in a double pass optical system.We prove an additivity property for radial variance that allows us to distinguish between spot blurs from macro-aberrations and micro-aberrations.When the method is applied to tear break-up in the human eye, we find that micro-aberrations in the second pass accounts for about 87% of the double pass image blur in the Shack-Hartmann wavefront aberrometer under our experimental conditions.

View Article: PubMed Central - PubMed

Affiliation: School of Optometry, Indiana University, 800 Atwater Avenue, Bloomington, Indiana 47405, USA. jnam@indiana.edu

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Classification of wavefront aberrations according to the order of Zernike polynomials used to represent the wavefront. The magnitudes of the aberration coefficients are not shown here. LOA: low order aberrations, HOA: high order aberrations, VHOA: very high order aberrations.
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g001: Classification of wavefront aberrations according to the order of Zernike polynomials used to represent the wavefront. The magnitudes of the aberration coefficients are not shown here. LOA: low order aberrations, HOA: high order aberrations, VHOA: very high order aberrations.

Mentions: In order to describe ocular aberrations with a wavefront error map spanning the full extent of the eye's pupil, we sample the emerging wavefront at numerous locations using an array of non-overlapping sub-apertures. For an aberrometer employing a Shack-Hartmann wavefront sensor (SHWFS), the subapertures are defined by the faces of individual lenslets in the array. If the wavefront over individual subapertures is not flat, local small scale aberrations are present which will cause blur in the spot image produced by the lenslet. The classical design of the SHWFS assumes the lenslets have sufficiently small diameter that the wavefront is approximately planar over each subaperture. In this case, all of the spot images are diffraction-limited Airy-disks free of aberration-induced blur and spot displacement is a measurement of wavefront tilt over each lenslet. In effect, the wavefront for the whole pupil is being approximated by a surface tessellated by flat tiles. The SHWFS determines the slope of each tile by measuring the displacement of each spot from the optical axis of the corresponding lenslet. The wavefront is then reconstructed from slope measurements mathematically by algorithms that either retain all features of the slope data (i.e. zonal reconstruction) or that smooth the wavefront to deemphasize local irregularities (i.e. modal reconstruction) (Fig. 1Fig. 1


Forward light scatter analysis of the eye in a spatially-resolved double-pass optical system.

Nam J, Thibos LN, Bradley A, Himebaugh N, Liu H - Opt Express (2011)

Classification of wavefront aberrations according to the order of Zernike polynomials used to represent the wavefront. The magnitudes of the aberration coefficients are not shown here. LOA: low order aberrations, HOA: high order aberrations, VHOA: very high order aberrations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368325&req=5

g001: Classification of wavefront aberrations according to the order of Zernike polynomials used to represent the wavefront. The magnitudes of the aberration coefficients are not shown here. LOA: low order aberrations, HOA: high order aberrations, VHOA: very high order aberrations.
Mentions: In order to describe ocular aberrations with a wavefront error map spanning the full extent of the eye's pupil, we sample the emerging wavefront at numerous locations using an array of non-overlapping sub-apertures. For an aberrometer employing a Shack-Hartmann wavefront sensor (SHWFS), the subapertures are defined by the faces of individual lenslets in the array. If the wavefront over individual subapertures is not flat, local small scale aberrations are present which will cause blur in the spot image produced by the lenslet. The classical design of the SHWFS assumes the lenslets have sufficiently small diameter that the wavefront is approximately planar over each subaperture. In this case, all of the spot images are diffraction-limited Airy-disks free of aberration-induced blur and spot displacement is a measurement of wavefront tilt over each lenslet. In effect, the wavefront for the whole pupil is being approximated by a surface tessellated by flat tiles. The SHWFS determines the slope of each tile by measuring the displacement of each spot from the optical axis of the corresponding lenslet. The wavefront is then reconstructed from slope measurements mathematically by algorithms that either retain all features of the slope data (i.e. zonal reconstruction) or that smooth the wavefront to deemphasize local irregularities (i.e. modal reconstruction) (Fig. 1Fig. 1

Bottom Line: An optical analysis is developed to separate forward light scatter of the human eye from the conventional wavefront aberrations in a double pass optical system.We prove an additivity property for radial variance that allows us to distinguish between spot blurs from macro-aberrations and micro-aberrations.When the method is applied to tear break-up in the human eye, we find that micro-aberrations in the second pass accounts for about 87% of the double pass image blur in the Shack-Hartmann wavefront aberrometer under our experimental conditions.

View Article: PubMed Central - PubMed

Affiliation: School of Optometry, Indiana University, 800 Atwater Avenue, Bloomington, Indiana 47405, USA. jnam@indiana.edu

Show MeSH
Related in: MedlinePlus