SVV vs Subjective Visual Vertical SVV

Subjective Visual Vertical (SVV) is a test that measures the difference between a person’s perceived vertical and the true vertical. It evaluates gravity perception mediated by the otolith organs, vestibular nerve, and central vestibular pathways, and helps detect asymmetry of vestibular function. Using an audio/video remote control or a variety of game controllers, including those for Nintendo Switch, PlayStation, and Xbox, the user adjusts a displayed line until it is perceived as perfectly vertical. After repeating this procedure 10 times, the application calculates the mean deviation from the true vertical and the standard deviation.

Subjective Visual Vertical turns your iPhone into a simple tool for checking how well a person can set a line to true vertical using sight alone — a quick way to screen for inner-ear (otolith) and balance differences. The app shows a line and uses the phone's motion sensors to know which way is truly vertical. The patient adjusts the line until it looks upright to them, and the app reports how far that is from true vertical, in degrees. TWO WAYS TO TEST • Bucket mode — fix the phone inside the base of a bucket with reusable putty, screen facing in. The patient holds the open rim to their face so the room is hidden, then turns the bucket until the line looks straight. • VR mode — drop the phone into a VR viewer or Google Cardboard. The line is shown to each eye in a split view. The patient turns the line with on-screen buttons or a Bluetooth remote and locks it in when it looks vertical. FLEXIBLE TESTING • Choose the right eye (OD), left eye (OS), both eyes (OU), or all in turn. • Run a single measurement or repeat each condition several times. • Set the trial length and the pause between trials. • Repeated trials are averaged automatically, with the standard deviation shown. CLEAR RESULTS • See the deviation in degrees for each eye, with a simple diagram of the perceived vs. true vertical. • Share the numbers as text, with no image attached. • In bucket mode you can record a photo or video of the trial with the true and perceived vertical lines drawn over it, and a date-and-time label. Media is saved to your own Photo Library. • Customisable line and background colours. • Right eye (OD) listed first, by convention. • Works with a Bluetooth remote so the line can be turned while the phone is sealed in a viewer. • Everything runs on the device. No account, no sign-in, no tracking. IMPORTANT This app is for educational purposes only and should not be used for clinical diagnosis or treatment decisions. It is not a medical device and has not been validated for clinical use. Always consult qualified healthcare professionals for medical advice.