Home Forums XR Discussions Tracking Eye movements with Strabismus

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    Hello everyone,
    I am trying to figure out if the technology is able to provide eye tracking data of each single eye separately.
    People with Strabismus (or crossed eyes) are only able to see using one eye at a time.
    Most are either using one eye only (sometimes referred to as a lazy eye condition),
    while others are constantly switching eyes which causes the unused eye to gaze inwards (esotropia) or outwards (exotropia).

    We are working with VR headsets and I was wondering if tobii’s eye tracking technology would work on people with this condition accurately?
    Is it possible to use the SDK to get data per eye (therefor determining the gaze direction of each eye)?

    What VR device would be most recommended for this type of experiment?

    If there are known projects you are familiar with I would love to hear about it 🙂

    Any help would be very much appreciated!
    Thanks so much.


    Hi Assaf,

    Can you share a bit what your application will do with the eye tracking?

    If it is to implement gaze interactions where you want to make sure it works for all of your users?




    Thank you for your reply Denny,
    Our application is meant to implement object tracking, for example if a ball is moving, make sure that the user is looking the ball and not at something else.
    Gaze interactions is definitely a feature we would want to implement but not at first stage.
    We are currently at the planning phase of a basic game for kids (Medical), which is meant to check attention and distraction and many of these kids have eye conditions.
    So it is more important for us to support only users with Strabismus and not all users if it makes a difference.

    The main issue is knowing if we can determine accurately that the user looking at the ball when both eyes are not looking at the same direction.
    If the SDK provides data per eye we can implement our own algorithm to calculate gaze direction (Strabismus usually has a fixed angel, and this is how we can determine which eye is not being used – it’s more complicated than that but I think the idea is clear…)

    Thanks so much,


    From browsing the documentation this doesn’t seem possible.
    Can anyone from Tobii confirm?


    Grant [Tobii]

    Hi @assafwint, thanks for your patience whilst we investigated this issue. Unfortunately, I can confirm that neither the SRanipal SDK nor the Tobii XR SDK provides separate eye gaze directions vectors.

    As the Tobii XR SDK operates directly on top of the Sranipal SDK layer, we are unable to provide this variable.

    Our recommendation is that you create a similar post on HTC’s own support forum with the intention of proposing this feature request.

    Our apologies for the disappointing news, we hope you are able to find some workaround for your needs.

    Please do get in touch again should you require any further information. Best Wishes.


    Hi @Grant, thank you for your kind response.
    So I have just one more question to be clear, if I have Strabismus or if I can only see with one eye, then eye tracking enabled products won’t work for me?

    I will try the HTC forums and will update here if any progress is made for other to know 🙂

    Thanks again!


    The direction that we are going is to have just a single gaze ray for targeting. One of the reasons is that we want eye tracking to work for all, without the developer needing to be knowledgeable about different eye conditions that might require special handling. With the single gaze ray, we can take care of these kinds of complexities. XR is still in early days and there might be some gaps between where we are in some products and where we want to be, but I’ll make sure to your voice internally.

    I’m sure that we can support your use case with the our eye trackers though, I wonder if it might be better to contact someone from Tobii since it seems to be a speciality market application.


    Thank you so much for all your help, I will keep following in hope for new innovations in the future.
    In the meanwhile I will try to figure out a workaround.

    Assaf W.

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