Antonia Steger

Advisors
Wolfgang Mehringer, Markus Wirth, Prof. Dr. Björn Eskofier,  Prof. Dr. Georg Michelson

Duration
08/2020 – 02/2021

Abstract
Amblyopia is a disease of the visual system, which often leads to a reduction in visual acuity in the affected eye [1]. One cause of amblyopia is strabismus, a malfunction in which the movement of the eyes is not symmetrical, hence, they cannot focus on the same point [1, 2]. The disease often arises in early childhood and should be diagnosed and treated as soon as possible to avoid a lifelong visual impairment [3]. The common treatment over the last decades for amblyopia in children was and still is patching. The healthy eye is covered with a patch so that the brain is forced to process the information from the amblyopic eye [4]. However, the therapy has disadvantages [5]. First, it has medical disadvantages: While patching improves visual acuity, it reduces the ability of depth perception. This is due to the patients only allowed to use one eye while the other is patched [1]. Secondly, there are psychological issues especially for children: On the one hand they are restricted in their activities because of the reduced visual performance. On the other hand young children tend to not understand why the healthy eye is covered and they are forced to use the amblyopic eye [4, 5]. With the advent of Virtual Reality (VR) technology new possibilities arise to the treatment of amblyopia in which both eyes are used simultaneously, also called binocular treatment [6]. The advantage of binocular treatment in VR is the ability to show distinct images to each eye. In this way, it is possible to equalize the image quality of the non-amblyopic eye. Thus, the brain accepts both visual inputs and both eyes are forced to work together [7]. This can directly train the binocular performance. Regularly applied to an amblyope can help to cure the visual disease.

Such a binocular treatment is already realized as VR game and parts of the game are published [8]. This game consists of three parts: First the strabismus measurement to compensate any misalignments, second the suppression measurement to equalize the image quality of both eyes
and enable binocular vision, and third the ball game which trains stereoacuity with defined disparity settings. However, the application is currently solely available for a wired VR headset, the HTC Vive 1. This device is operated by a high-performance computer and additionally requires a permanently installed tracking system to allow the headset to determine its position in the room. This complex hardware setup increases the costs for the game and introduces the risk of user errors. Additionally, it is inflexible in its use due to the permanently installed tracking system that has to be recalibrated when relocated. These complicate a periodic usage at home which is important for a successful therapy of amblyopia.

The goal of this thesis is to modify the implemented binocular treatment in a way that it can be used on standalone VR devices. The advantage of these VR devices is that only headset and controllers are needed. The headset locates itself in the room and the controllers are tracked
relative to the headset. This minimizes the effect of the above mentioned disadvantages, because the device is reduced in costs and can easily be used at home and by the patient. The main modification addresses the graphics of the application. The already implemented application must
be reduced in complexity so that it fits the computing power of standalone VR devices. Furthermore, the program should be user-friendly. After successful modification of the application there will be a study to compare the functionality and usability. The aim is to show that there is
no difference in functionality but the usability of the new device has improved for the use at home.

References:
[1] Holmes J., Clarke M. Amblyopia. Lancet 367, 1343–1351, 2006.
[2] Levi D. Visual Processing in Amblyopia: Human Studies. Strabismus 14(1), 11-19, 2006.
[3] Holmes J., Lazar E., Melia B., et al. Effect of Age on Response to Amblyopia Treatment in Children. Arch Ophthalmol 129(11), 1451-1457, 2011.
[4] Searle A., Vedhara K., Norman P., et al. Compliance with eye patching in children and its psychosocial effects: A qualitative application of protection motivation theory. Psychology, Health & Medicine 5(1), 43-54, 2000.
[5] Hess R., Thompson B. Amblyopia and the binocular approach to its therapy. Vision Research 114, 4-16, 2015.
[6] Foss A. Use of video games for the treatment of amblyopia. Curr Opin Ophthalmol 28, 276-281, 2017.
[7] Eastgate, R., Griffiths, G., Waddingham, P. Modified virtual reality technology for treatment of amblyopia. Eye 20, 370–374, 2006.
[8] Mehringer W., Wirth M., Gradl S., et al. An Image-Based Method for Measuring Strabismus in Virtual Reality. In: IEEE International Symposium on Mixed and Augmented Reality, Recife, Brazil, 2020.