title: Corneal primary aberrations compensation by oblique light incidence.
abstract: The eye is not a centered system. The line of sight connects the fovea with the center of the pupil and is usually tilted in the temporal direction. Thus, off-axis optical aberrations, mainly coma and oblique astigmatism, are introduced at the fovea. Tabernero et al. [J. Opt. Soc. Am. A 24(10), 3274-3283 (2007)] showed that a horizontal tilt of the crystalline lens generates a horizontal coma aberration that is compensated by the oblique light incidence on the eye. Here we suggest that corneal astigmatism may also play a role in compensation of oblique aberrations, and we propose a simple model to analyze such a possibility. A theoretical Kooijman eye model with a slight ( approximately 0.6 D) with-the-rule astigmatism is analyzed. Light rays at different incidence angles to the optical axis are considered, and the corresponding point spread functions (PSFs) at the retina are calculated. A quality criterion is used to determine the incidence angle that provides the narrowest and highest PSF energy peak. We show that the best image is obtained for a tilted incidence angle compatible with mean values of the angle kappa. This suggests that angle kappa, lens tilt, and corneal astigmatism may combine to provide a passive compensation mechanism to minimize aberrations on the fovea.
authors.affiliation: Universidad de Alicante, Department Optica, Campus S Vicente, San Vicente del Raspeig, Alicante 03690, Spain.
authors.forename: Julian
authors.initials: J
authors.lastname: Espinosa
authors.forename: David
authors.initials: D
authors.lastname: Mas
authors.forename: Henryk T
authors.initials: HT
authors.lastname: Kasprzak
mesh_terms: D003198:Computer Simulation; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography / Q000379:methods*; D006801:Humans; D008027:Light; D008954:Models, Biological; D012030:Refractive Errors / Q000503:physiopathology*; D012542:Scattering, Radiation; D014785:Vision, Ocular