Abstract
A polar coordinate system should be used when defining (a) the half-meridian and (b) the eccentricity of the center of the test target, both expressed in degrees. The zero degree half-meridian is defined to the right of the patient (as seen by the patient). The specified half-meridian then proceeds counterclockwise through 360° about the fixation target (as seen by the patient). The fixation point is defined at having zero degree eccentricity. This assumes the patient has normal fixation.
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Notes
Distinguish between ability to specify a location and an area.
Lens factors also influence accuracy of location and re-location of a target in the visual field. Apparent location of a target is influenced by power and centration of the lens correction, vertex distance, base curve and lens thickness. It is desirable that the lens(es) used and the vertex distance be noted. There is an advantage in keeping vertex distance small.
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© 1979 Dr. W. Junk bv Publishers
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Concilium Ophthalmologicum Universale. (1979). Specification of the location of an Object in the Visual Field. In: Perimetric Standards and Perimetric Glossary. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-9639-7_7
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DOI: https://doi.org/10.1007/978-94-009-9639-7_7
Publisher Name: Springer, Dordrecht
Print ISBN: 978-94-009-9641-0
Online ISBN: 978-94-009-9639-7
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