Optonet Vision Unit Documentation
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3.5.4.Landolt Optotype "C"
The program also includes a Landolt “C” chart. The Landolt “C” optotype has traditionally been considered the standard in the measurement of VA, from which the other optotypes should be calibrated.8 Five orientations of the gap in the Landolt “C” are used: right, left, up, down and diagonal (at 45 degrees).
By pressing an icon in the tools menu (or the P key) additional oblique orientations can be added (135, 225 y 315º) for a total of eight positions. The additional options reduce the likelihood of guessing correctly. This chart conforms to the ISO 8596 standard, which recommends using 8 orientations.
The Landolt “Cs” can be used in patients who cannot complete a letter chart. This is not recommended for children because most cannot reliably indicate the different orientations before about 7 years of age.