A new instrument for measuring visual strain caused by video data terminal operations

In order to measure the visual strain caused by continuous video data terminal (VDT) operations, a new instrument is constructed utilizing both the personal computer and the software, in which a series of Landolt´s rings used to test the visual sensation are demonstrated on the computer display, since the visual strain is accumulated during the VDT operations. For the VDT operations, the Landolt´s rings demonstrated on the computer display check if the results of the visual strain tests indicate the state that the accumulated visual strain has exceeded the maximum acceptable limit. Using this new instrument, continuous VDT operations for 90 minutes were found to cause remarkable visual strain which is unacceptable for each VDT operator. The results of the tests utilizing this new instrument have confirmed that a coffee break is needed after a continuous VDT operation for 90 minutes.