Zeiss HUMPHREY 720i User Manual - page 295

Appendix D: Goldmann Conversion Tables

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HUMPHREY FIELD ANALYZER II -

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The decibel notation the Field Analyzer uses can be expressed in terms of Goldmann units or

apostilbs. The conversion between decibels (dB) and apostilbs (asb) and Goldmann units are

listed in Table D-1. For example, a threshold sensitivity of 25 dB using a size III stimulus is equal

to a Goldmann III-Ie stimulus or 32 asb. A threshold sensitivity of 0 dB using a size III stimulus is

equivalent to a Goldmann V 4e stimulus or 10,000 asb. A simplified chart to convert from dB

values to Goldmann units is available in Tables D-1 through D-6.

To use the conversion tables, first locate the table which lists the target size you used for the test.

For example, you may have completed a central 30-2 threshold test using a size III target and you

want to find out what the Goldmann equivalent is for 15 dB. Using Table D-4, find 15 dB. Read

the horizontal and vertical columns that intersect at 15 dB. The Goldmann equivalent is either a II

4e, III 3e, IV 2e, or V 1e.

      Stimulus Size

Angular Subtense

Stimulus Area (30 cm Bowl)

    (degrees)

(mm

2

)

   Size I

        0.11

  1/4

   Size II

        0.22

    1

   Size III

        0.43

    4

   Size IV

        0.86

   16

   Size V

        1.72

   64

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