title: Shack-Hartmann-based objective straylight assessment of the human eye in an increased scattering angle range.
abstract: Objective measurement of straylight in the human eye with a Shack–Hartmann (SH) wavefront aberrometer is limited in imaging angle. We propose a measurement principle and a point spread function (PSF) reconstruction algorithm to overcome this limitation. In our optical setup, a variable stop replaces the stop conventionally used to suppress reflections and scatter in SH aberrometers. We record images with 21 diameters of the stop. From each SH image, the average intensity of the pupil is computed and normalized. The intensities represent integral values of the PSF. We reconstruct the PSF, which is the derivative of the intensities with respect to the visual angle. A modified Stiles Holladay approximation is fitted to the reconstructed PSF, resulting in a straylight parameter. A proof-of-principle study was carried out on eight healthy young volunteers. Scatter filters were positioned in front of the volunteers’ eyes to simulate straylight. The straylight parameter was compared to the C-Quant measurements and the filter values. The PSF parameter shows strong correlation with the density of the filters and a linear relation to the C-Quant straylight parameter. Our measurement and reconstruction techniques allow for objective straylight analysis of visual angles up to 4 deg.
authors.affiliation: Technische Universität Ilmenau, Institute of Biomedical Engineering and Informatics, Department of Computer Science and Automation, Gustav-Kirchhoff-Straße 2, 98693 Ilmenau, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schramm
authors.affiliation: GMC Systems mbH, Albert-Einstein-Str. 3, 98693 Ilmenau, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Schikowski
authors.affiliation: Technische Universität Ilmenau, Institute of Biomedical Engineering and Informatics, Department of Computer Science and Automation, Gustav-Kirchhoff-Straße 2, 98693 Ilmenau, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Lerm
authors.affiliation: GMC Systems mbH, Albert-Einstein-Str. 3, 98693 Ilmenau, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Kaeding
authors.affiliation: Technische Universität Ilmenau, Institute of Biomedical Engineering and Informatics, Department of Computer Science and Automation, Gustav-Kirchhoff-Straße 2, 98693 Ilmenau, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Haueisen
authors.affiliation: University for Health Sciences, Medical Informatics and Technology, Institute of Electrical and Biomedical Engineering, Eduard Wallnöfer-Zentrum 1, Hall in Tirol 6060, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Baumgarten
mesh_terms: D005123:Eye / Q000000981:diagnostic imaging*; D064368:Healthy Volunteers; D006801:Humans; D008027:Light; D061848:Optical Imaging / Q000379:methods*; D011680:Pupil; D012542:Scattering, Radiation; D014785:Vision, Ocular