title: Construction of a model eye and its applications.
abstract: Construction details are given of a model eye, based on the Bennett and Rabbetts schematic eye. It incorporates a cornea, lens, and spherical fundus. Distilled water filled the anterior and vitreous chambers. By means of a micrometer screw, the vitreous chamber depth can be precisely varied to produce axial ametropia from +11 to -17 D. Readings taken over the greater part of this range with a Topcon Autorefractor RM-A6500 were found to be repeatable and reproducible within +/- 0.25 D. The model eye was used to investigate the relationship between the actual size of a fundus feature and its photographic image in two different fundus cameras. With a Zeiss Oberkochen camera of telecentric design the magnification was found to remain constant whatever the degree of axial ametropia, whereas with a Carl Zeiss Jena camera the magnification varied linearly with ametropia. A technique developed by Littmann for determining the actual size of a retinal feature when using a fundus camera of telecentric design is discussed briefly.
authors.affiliation: Applied Vision Research Centre, City University, London, UK.
authors.forename: A R
authors.initials: AR
authors.lastname: Rudnicka
authors.forename: D F
authors.initials: DF
authors.lastname: Edgar
authors.forename: A G
authors.initials: AG
authors.lastname: Bennett
mesh_terms: D005123:Eye / Q000033:anatomy & histology*; D006801:Humans; D008433:Mathematics; D008953:Models, Anatomic; D012029:Refraction, Ocular; D012031:Refractometry