Real Time Simulator of Age-Related Macular Degeneration

Introduction

Important applications of Virtual Reality (VR) have been in the context of medical research. For this project, we have simulated some of the typical symptoms of age related macular degeneration (AMD) within a Unity3D environment, to be displayed via Oculus Rift. The goal was to produce visual effects subtle enough to capture the actual experience of affected patients. Once the results are deemed accurate via subjective comparison, this setup could be used not only as a pseudo-phenomenological model but also as a starting point for further simulation and testing of visual acuity or impairment. Additionally, it has the potential of conveying to healthy individuals, e.g. family, friends and physicians, the experience of a person suffering from AMD.

Background

AMD generally affects individuals above the age of 60, though symptoms may begin earlier and are not always noticeable at the onset. The region of the retina that is affected by AMD is called the macula and includes the center point of the visual field (the fovea). This corresponds to the point of fixation, and is the most sensitive to spatial and chromatic detail.

Based on the cause, AMD can assume one of two forms. Dry AMD occurs when yellow protein deposits called drusen accumulate underneath the macula. Dry AMD also occurs when the photoreceptors or surrounding tissue actually break down, causing gaps in the retinal image. This can lead to partial or total loss of central vision.

Wet AMD occurs by neovascularization, where retinal blood vessels expand and leak fluid into the macula, damaging and distorting its surface. This can lead, again, to vision loss, but also introduces warping since straight lines appear curved (a condition called metamorphopsia). Out of all patients affected by AMD, 10% have the wet form, and are more likely to experience permanent loss of vision at the fovea.

Methods

Rendering Pipeline

• Rendering environment: Unity
• Shader scripting, Cg/HLSL
• Shader components can be easily scripted and attached to any Camera element as post-processing effects
• Oculus Rift for stereo playback

Simple use of two Camera views

Implementation Scotoma simulation:

• desaturation: CIE 1931
• gaussian blur
• dark spot
• warping
• manual transformation
• gaussian BPF to generate noise textures

Conclusions

Real time textural + structural inpainting Live capture must account for distance assume a given point of fixation or incorporate depth sensing the lack of stimulus does not entail lack of perception, especially when motion is considered => real time rendering Extensive subjective testing to measure the accuracy of each effect

Future Work

• Real time textural + structural inpainting
• Live capture

must account for distance

assume a given point of fixation or incorporate depth sensing the lack of stimulus does not entail lack of perception, especially when motion is considered => real time rendering

• Extensive subjective testing to measure the accuracy of each effect

Appendix

Related Literature

• Freeman, Jeremy, and Eero P. Simoncelli. "Metamers of the ventral stream." Nature neuroscience 14.9 (2011): 1195-1201.
• Marmor, David J., and Michael F. Marmor. "Simulating vision with and without macular disease." Archives of ophthalmology 128.1 (2010): 117-125.
• Lewis, J., L. Shires, and D. J. Brown. "Development of a visual impairment simulator using the Microsoft XNA Framework." Proc. 9th Intl Conf. Disability, Virtual Reality & Associated Technologies, Laval, France. 2012.
• Ai, Zhuming, et al. "Simulation of eye diseases in a virtual environment." System Sciences, 2000. Proceedings of the 33rd Annual Hawaii International Conference on. IEEE, 2000.
• Jin, Bei, Zhuming Ai, and Mary Rasmussen. "Simulation of eye disease in virtual reality." Engineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the. IEEE, 2005.
• Ates, Halim Cagri, Alexander Fiannaca, and Eelke Folmer. "Immersive simulation of visual impairments using a wearable see-through display." Proceedings of the Ninth International Conference on Tangible, Embedded, and Embodied Interaction. ACM, 2015.
• Lewis, James, et al. "Simulating visual impairments using the Unreal Engine 3 game engine." Serious Games and Applications for Health (SeGAH), 2011 IEEE 1st International Conference on. IEEE, 2011.

Oculus Specifications

• Display Technology: OLED
• Resolution: 2160×1200 (1080×1200 per eye)
• Refresh Rate: 90 Hz
• FOV (Nominal): 110 degrees or greater
• Head Tracking: 6DOF (3-axis rotational tracking + 3-axis positional tracking)
• Weight: TBA (Lighter than 380g)
• Platforms: Microsoft Windows (OS X and Linux planned)

Connection: 1x HDMI 1.3 and 2x USB 3.0