Optonet Vision Unit Documentation

Please note that this User Guide is being currently updated; new sections will be added shortly.

3.4.8.Intermediate Steps #

The Optonet vision unit incorporates another novel feature, by adding an intermediate VA level between each row. This is a unique feature that currently is not available with any other acuity testing system.  The intermediate levels allow a more accurate VA measurement.

This function can be very useful when a more precise measurement of the VA is required.  For example, current (very expensive) treatments for age-related macular degeneration (AMD) are based upon acuity measures; however, in these patients the reliability of VA measurement is very low, with great variations from one day to the next.5 In this situation it is important to have a tool to measure the VA with the maximum possible precision which can be achieved using the intermediate steps.

To activate the intermediate step feature, click the 1/2 step icon in the tools menu (available with any of the optotypes). The new scale can also be accessed by typing “P”.



The optotypes are still calibrated on a logarithmic scale, with a size change equivalent to 0.05 instead of 0.1 log units. Calculating acuity is simple using the VAR notation: each letter that sees the patient is assigned a value of 0.5 instead of 1.

Once the 1/2 step function is selected, this option is saved automatically, so that the next time the program is opened, the intermediate steps option is activated already. This is useful for professionals who prefer to always work with intermediate steps.

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