I.R.I.S. Readiris 14 for Mac User Guide - Manual (Page 121)

How To
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 Install your scanner's Twain driver.
In general, drivers can be found on the CD-ROM provided with
your scanner and on the website of your scanner manufacturer.
They are not provided by I.R.I.S. Note that some scanner drivers
may not work under the latest versions of Mac OS. See the
documentation supplied with your scanner to find out which
platforms are supported. If necessary, contact your scanner
manufacturer.
IRIScan scanners
 Connect your *IRIScan scanner to your Mac and power it on.
 Install your scanner's Twain driver.
*Note that you do not need to install any drivers when using an
IRISCard Anywhere, IRIScan Anywhere or IRIScan Book
scanner. They are not Twain driver-based scanners that can be used
from within any application to scan documents. Instead, they are
designed to be used on their own, disconnected from any computer.
The documents you scan are stored in the scanner’s internal
memory (or optional SD card / USB flash drive). From there they
can be loaded directly into Readiris when you connect the scanner
or insert the SD card or USB flash drive into your Mac.
To check if the scanner driver has been installed successfully:
 In the Readiris menu, click Preferences.
 Click the Scanner tab.
 You should see your scanner listed.