Questions and Answers
Q. I suffer with Alternating Exotropia or Esotropia how do I set-up Equal-Eyes
If your eyes have equal acuity it can be hard to determine which eye is weaker than the other. You may also be suffering with alternating eso or exotropia, in which case you should perform Step 1.
Step 1.
I would recommend selecting the eye that is the opposite of your right handedness. Eg if you are right handed consider your left eye as the weak eye and vice versa if you are left handed.
In this scenario enter the setup page and reduce the brightness of the right eye until you observe the setup cross as two images, effectively double vision.
If you are already seeing two images ie you suffer with double vision the you may skip the above step and move on to Step 2.
Step 2.
In the setup page, add some error correction in the Horizontal, Vertical and Rotational Planes as per this link https://avalonweb.com.au/demo/home/quest-2-configuration/
Step 3.
Once the error correction has been applied. Remove a small amount of correction in each plane, but only to the point to where you are able to use your eyes to re-align the image.
Over the months, the amount of error correction should be removed as you progress with the therapy.
Step 4.
Perform the various exercises and games within Equal-Eyes.
Q. What are the limitations for configuration of the image shift. Is there a squint angle the VR app is not able to support?
Below are the measured specs for an Oculus Quest 2.
Although the image quotes 90 degrees, it is closer to 89 degrees
(As specified by Meta).
With Esotropia (Eyes pointing towards the nose) the areas in
orange will be the usable field of view for your condition with
the Quest 2 for each eye.
So Effectively, you have 89 degrees to play with. The useful
amount of the scene you are able to view will be:
89 degrees minus (Your angular disparity).
If you have more than 45 degrees of disparity it will start
becoming more restrictive for peripheral vision. The quest 2 will
work with up to 89 degrees for central vision but of course
provide very little real estate for the exercises.
If you have 45 degrees or less then you will have a reasonable
amount of usable area.
(see the attached image).
Q. I know my Prism Diopter (PD), how is that handled in Equal-Eyes?
This adjustment has a usable range of up to 45 degrees (effectively 100 PD). See above. Regarding the Inter pupilar distance (IPD) referenced in the above diagram Both the Quest 2 and Quest 3 have adjustments for IPD and can vary from about 5.4 to 7cm. The Quest 2 has 3 fixed positions whilst the Quest 3 has a variable adjustment. Therefore allowances for the PD need to be calculated for higher ranging Prism Diopters (PD)'s
Q. Does Equal-Eyes utilise Dichoptic Training?
Yes it does. Dichoptic training is achieved by adjusting the brightness of the strong eye to a degree where both eyes are being processed by the cortex. Virtual eye re-alignment is then applied by artificially adjusting the rotational angles of the images applied to both eyes.
This adjustment has a usable range of up to 45 degrees (effectively 100 PD) Horizontal or Vertical planes.
Additionally Rotation error can also be applied.
The amount of error is reduced over time as the eye motor control adapts to the adjustments.
Q. How Much Error Correction Should I remove as I progress?
This will vary from person to person. A small amount is recommended. As a starting point perhaps 0.5 degrees per month. You may find this is either too much or too little. In which case make the adjustments accordingly.
You should aim to reduce the error correction with comfortable increments. Do not push your eyes too hard, this can lead to discomfort, headaches etc.
The key to any exercise is to do it in bite sized steps. This will help you both psychologically and physically. Repetitiveness and endurance is the key to your success.
Q. I Wear Prescription Glasses, Can they be used with the Quest 2?
Yes they can. The Quest 2 is supplied with an adapter surround that creates more depth between the Quest 2 optics and the wearer. This does limit the FOV slightly but provides a means to cater for your glasses.
An alternative is to use built in prescription lenses. I have personally used Reloptix Lenses and highly recommend them for ease of use and comfort. Using the above link will provide you with a slight discount on these already affordable lenses.
Q. I Wear Prescription Glasses, Can they be used with the Quest 3?
Yes they can. The Quest 3 has depth adjusters in the side walls of the headset. Use these to adjust the distance between your eyes and your lenses to make from for you glasses.
An alternative is to use built in prescription lenses. Reloptix are taking pre-orders for Quest 3 prescription lenses. If they are anything like the ones I've tested for the Quest 2 I would highly recommend them for ease of use and comfort. Using the above link will provide you with a slight discount on these already affordable lenses.
Q. What is the Focal Length of the Quest 2 or 3?
It is fixed at about 4ft or 1.2 metres.
Q. Are there any known anomalies in VR over real life vision?
Yes there are
Resolution is limited to about 20 pixels per degree of eye movement. In real life your visual resolution in theory is a lot higher this is due the the fovea which covers about 2 degrees of the high resolution of our eyes is processing the scene in very high detail typically equivalent to a 9 mega pixel camera. On top of that slight movement of the eye increases this resolution by combining the images seen with tiny alterations in angle to form a very detailed analogue image as opposed to a digital image.
VR is fundamentally alien to our eyes. There is a system where the eyes not only converge on a subject but also focus on a subject. For near objects the lens will adjust to focus as well as converge. AC/A Ration. When switching to distant objects the eyes will diverge slightly to effectively converge on the distant abject. The focus will also change.
The relationship between focusing and converging is known as the Accommodative Convergence to Accommodation Ratio (see AC/A Ratio). As the focal length of the VR Headset is typically 1.2 metres and fixed, the brain will try to adjust focus as VR objects vary in distance and will cause the brain slight confusion. This can lead to blurry vision, motion sickness or headaches.