1 Principles of VNG Analysis Amanda Cerka Mroz, M.A., CCC-A 3 Principles of VNG analysis 1. Set up for success 2. Clean up responses 3. Assess each result 4. Check your work 4 1. Set up for success • Goggle placement – Optimal data collection depends on optimal camera positioning! •V i d
2 5 Goggle placement 1. Click on Video Adjust – View eyes while placing the camera 2. Loosen the back and top headbands on the goggles 3. Place the goggles on the bridge of the patient’s nose and pull the back headband over the patient’s head 4. Position the goggles so that pupils are center and level 5. Tighten the headbands – Goggles should be snug; patient may have “raccoon eyes” afterwards 6. Fine-tune the positioning with the knobs (H,F,V) 6 Goggle placement Horizontal Focus Vertical H orizontal knob: adjusts the distance between the cameras F ocus knob: adjusts the distance between the cameras and the patient’s pupils V ertical knob: adjusts the camera up and down *Most commonly used 7 Goggle placement tips • Position the back headband as low as it can go – Below the inion if possible – The two straps of the back headband may be positioned so that one is above inion and other is below • Make sure the top headband is straight – Generally need to leave this with as much length as possible – The top headband can assist with raising and lowering the goggles on the patient’s face
3 8 Video Adjust • Auto-adjust is a good place to start • Manual adjust should be used for optimizing the image – Brightness and Contrast can be done individually or for both eyes together; Threshold affects both eyes Adjust Both Eyes is for manual adjustment of Brightness and Contrast 9 Video Adjust Poor video adjustment = Poor tracing 10 Video Adjust • Watch the crosshairs as patient moves eyes side to side, up and down – Make sure crosshairs stay with pupils at extreme positions
4 11 Video Adjust tips • Dimly lit room is best for software to differentiate between pupil and iris – Light will affect software’s ability to auto-adjust – If there is a lot of light in the room, do the auto and manual adjust with the goggle cover closed • Adjustment settings are kept between patients – Auto-adjust not necessary for each patient – Manually tweak to optimize • Consider obtaining: – Make-up remover – White eye-liner pencil – Eyelash curler 12 Calibration • Calibration adjusts the recording system so that deflections correspond to amplitude of eye movements – The position of the patient in relation to the light bar affects the amount of eye movement required to follow the calibration stimulus • The required distance is 4 feet – Software assumes this distance during calibration – Sets outermost light at 30 degrees right/left (used for Gaze) • Acceptable range 3’8” to 4’4” – Range function on light bar monitors distance during testing 13 Calibration
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