The Gaze Graph; Head Tracking (Model 750I); Example Of A Gaze Graph: Good Fixation With A Large Number Of Blinks; Example Of A Gaze Graph Indicating Poor Fixation - Zeiss HUMPHREY 720i User Manual

TESTING

The gaze graph

Head tracking
(model 750i)
REV. B 02/03 PN 51680-1
The gaze graph is a useful method for documenting movement of the patient's test eye. A test
starts with no markings on the gaze graph. As time progresses, the graph expands from the
right, marking eye movement and blinks.
Upward markings indicate that the test eye deviated from the fixation target at the time of
stimulus presentation. The higher the marking, the greater the deviation. The direction of
deviation from the fixation target is not indicated. Only the magnitude is recorded.
Downward markings indicate that the gaze system could not locate the patient's gaze:
small downward markings indicate that the system was unable to detect gaze direction; large
markings indicate that the patient blinked while the stimulus was being presented. Minimal
deviation of the markings (depicted as a horizontal line) indicates excellent fixation. Refer to
Figure 5.3 for an example of a gaze graph that displays an example of good fixation. An
example of poor fixation is shown in Figure 5.4.
+10˚
0˚
blinks
Figure 5.3: Example of a Gaze Graph: Good Fixation with a Large Number of Blinks
+10˚
0˚
Figure 5.4: Example of a Gaze Graph Indicating Poor Fixation
The Head Tracking feature helps maintain proper alignment of the head and eye relative to the
trial lens holder. As part of the gaze initialization process, the HFA II analyzes and records the
patient's eye position. When Head Tracking is turned ON, the instrument will move the chin
rest in increments of 0.3 mm, readjusting the patient to the original Gaze Track initialization
position. Maintaining proper alignment during testing reduces trial lens scotoma and increases
the reliability and accuracy of test results.
Note: Head Tracking only works when the trial lens holder is in use and Gaze Tracking has
been successfully initialized. Head Tracking is only necessary when a trial lens is used. To
turn Head Tracking off during a test, press FIXATION to access the Change Fixation
Monitoring screen. Head tracking is only turned off for the length of the current test.
Large eye deviation
HUMPHREY FIELD ANALYZER II -
5-5
Good, steady fixation
i
series