title: Corneal topography, refractive state, and accommodation in harbor seals (Phoca vitulina).
abstract: Corneal topography of a harbor seal measured with a Placido's disc shows a central flattened stripe in the vertical meridian. Together with a pupil that can form a vertical slit, the flat vertical meridian can minimize the optical effects caused by the transition from water to air. Using infrared (IR) photoretinoscopy, we analyzed the refractive state of harbor seals and revealed a high degree of myopia and astigmatism in air, but emmetropia or slight hyperopia with little astigmatism underwater. The brightness distribution in the pupils suggest the presence of a multifocal dioptric apparatus in air and underwater. We found a first indication for accommodation by dynamic recordings underwater.
authors.affiliation: University of Freiburg, Institute of Biology I (Zoology), D-79112 Freiburg, Germany.
authors.forename: Frederike D
authors.initials: FD
authors.lastname: Hanke
authors.forename: Guido
authors.initials: G
authors.lastname: Dehnhardt
authors.forename: Frank
authors.initials: F
authors.lastname: Schaeffel
authors.forename: Wolf
authors.initials: W
authors.lastname: Hanke
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000388:Air; D000818:Animals; D003315:Cornea / Q000033:anatomy & histology* / Q000502:physiology; D019781:Corneal Topography; D008954:Models, Biological; D046049:Phoca / Q000033:anatomy & histology* / Q000502:physiology; D012029:Refraction, Ocular / Q000502:physiology*; D042262:Retinoscopy; D014867:Water
chemical_list: D014867:Water