Duration 5min, Q&A 3min
A System Devised to Monitor Fixation During Binocular Visual Field Testing
The conventional automated perimeters for binocular visual field (VF) testing cannot monitor fixation using the Heijl-Krakau method. Besides¸ it is impossible to use CCD camera to monitor fixation when the patient's head is positioned in front of the center of the perimeter's cupola. In this study¸ a system using a prism to monitor fixation during binocular VF testing was devised and its usefulness was evaluated.
Subjects were seven healthy volunteers (average age¸ 26.3 ± 2.8 years). The ophthalmic inclusion criteria were as follows: best corrected visual acuity of 1.2 (-0.1 logMAR equivalent) or better¸ refractive error within ±3.00 D sphere and ±1.50 D astigmatism, and normal stereopsis.
The Octopus 900 perimeter was used in this study. We mounted a removable prism to the camera hole on the perimeter. This method enabled the perimeter's own fixation control system to monitor the fixation when threshold was measured under binocular condition¸ and the fixation of each eye could be confirmed on the display while the subject's head was positioned in front of the center of the cupola. To evaluate the usefulness of this device¸ three threshold measurements were taken and compared using the device with the G program (59 test points): the left/right monocular thresholds with the tested eye aligned to the center of the cupola (referred to as "the conventional test position")¸ the left/right monocular thresholds with the subject's head positioned in front of the center of the cupola (referred to as "the binocular test position")¸ and binocular threshold.
Results and Conclusion
The fixation control system in the Octopus 900 perimeter worked for all the subjects when their measurements were taken in the binocular test position. No significant difference was seen between the monocular thresholds taken in the two positions either within the central 30° (p > 0.1) or beyond the peripheral 20° (p > 0.1). Binocular threshold was lower than monocular thresholds (p < 0.01). The false-positive and false-negative rates of reliability were both under 20% for all the test conditions and no reliability difference was seen between the two test positions.
By exploiting the perimeter's own fixation control system¸ our device effectively monitors fixation under binocular condition. It is an easy-to-use new method for binocular VF testing.
[ Keyword ]
binocular visual field / perimetry / monocular threshold / binocular threshold / fixation control system
[ Conflict of Interest ]