Examination Reliability - Kowa AP-7000 Instruction Manual

5.8. Examination Reliability

The reliability of an examination can be tested by 3 indices below.
5.8.1. Fixation Loss (Heijl-Krakau Method, H-K Method)
When the blind spot is being stimulated, the characters of "Fixation loss" are shown in orange in the lower right of the
examination screen. If a fixation loss occurs, the fixation target flashes twice and a voice message for alerting is given.
In the lower right of the screen, the fixation loss status and result are shown in units of percentage and in the format of
Number of blind spot responses/Number of blind spot stimulations.
As the value of Number of blind spot responses/Number of blind spot stimulations, that is, the fixation loss rate is
increased, the reliability of the examination result is decreased. If the value reaches 20% or more, the fixation loss rate
is shown in orange and XX appears on the left. XX also appears on the left of the percentage indication when printed.
If a fixation loss occurs frequently, the instrument automatically checks the position of the blind spot again.
Check the following in case of frequent fixation losses during the examination:
Check the patient's fixation through the eye fixation monitor. If the patient is not fixated, pause the
examination and instruct the patient to be properly fixated.
Check the position of the patient's eye through the eye fixation monitor. If the eye is not aligned, align the
eye with the fixation target again by stopping the examination and adjusting the chin rest.
Check that the eye not being examined is properly covered. If it is not properly covered, the patient can see
the stimulus of the blind spot.
The instrument may detect fixation loss frequently even though the things above are checked. In this case, tell the patient not
to worry about blinking of the fixation target in case of a fixation loss. Deactivate the buzzer for the fixation loss or
interrupt the examination and deactivate the fixation loss function, and then, proceed with the examination by checking
the fixation loss through the eye fixation monitor only.
For the evaluation of the fixation loss, fixation monitoring by the examiner through the eye fixation monitor and the result
of the gaze monitor function can also be used as reference.
5.8.2. False-positive Reaction
The motor to change a stimulus is moved at a fixed interval and not to present a stimulus. If a patient responds to the
movement or sound of the motor and pushes the button even though he/she does not see a stimulus, the number of
responses increases.
When the false – positive reaction examination is in progress, the characters of "False – positive reaction" are shown in
orange in the lower right of the examination screen. The progress status and result of the false – positive reaction
examination are shown in units of percentage and in the format of Number of responses/Number of examinations in the
lower right of the screen.
As the value of "Number of responses/Number of examinations" increases, the reliability of the examination result is
reduced. If the value reaches 33% or more, the false-positive reaction value is shown in orange and XX appears on the
left. In addition, XX also appears on the left of the percentage indication when printed.
5.8.3. False-negative Reaction
A stimulus may be presented in brighter intensity at a point the patient has already responded. If a patient is asleep or
lazy, the percentage increases, and this cannot be checked by the other reliability tests.
When the false – negative reaction examination is in progress, the characters of "False – negative reaction" are shown
in orange in the lower right of the examination screen. The progress status and result of the false – negative reaction
examination are shown in units of percentage and in the format of Number of nonresponses/Number of examinations
in the lower right of the screen.
As the value of "Number of nonresponses/Number of examinations" is increased, the reliability of the examination result
is reduced. If the value reaches 33% or more, the false-negative reaction value is shown in orange and XX appears on
the left. In addition, XX also appears on the left of the percentage indication when printed.
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