Vergence movements are closely connected to accommodation of the eye. Under normal conditions, changing the focus of the eyes to look at an object at a different distance will automatically cause vergence and accommodation, sometimes known as the accommodation-convergence reflex.

Conventional 3D displays present images on one surface, so focus cues (accommodation and blur in the retinal image) specify the depth of the display rather than the depths in the simulated scene. In addition, the vergence stimulus in conventional 3D displays varies depending on where the viewer looks in the simulated scene, but the focal distance remains fixed; the difference in those distances requires the viewer to uncouple vergence and accommodation.

The uncoupling of vergence and accommodation required by 3D displays frequently reduces one’s ability to fuse the binocular stimulus and causes discomfort and fatigue for the viewer.

Vergence–accommodation conflicts that vary quickly cause more visual discomfort than conflicts that vary slowly.


Articles

Watching 3D: What's It Doing To Our Eyes and Brains? at Tom’s Guide - 2011
Vergence at Wikipedia

Presentations

Executive Briefing: Basic Visual Perception Concepts Related to 3D Movies by Phil Lelyveld (Consumer 3D Experience Lab - USC) - 2009
Assessing vergence-accommodation conflict as a source of discomfort in stereo displays by Shibata, Kim, Hoffman, & Banks (UC Berkeley) - 2011

Publications

Vergence–accommodation conflicts hinder visual performance and cause visual fatigue by Hoffman, Girshick, Akeley & Banks () - 2008
The rate of change of vergence–accommodation conflict affects visual discomfort by Kima, Kanea & Banks - 2014
Resolving the Vergence-Accommodation Conflict in Head Mounted Displays by Kramida and Varshney - 2015
=> The vergence-accommodation conflict (VAC) remains a major problem in head-mounted displays for virtual and augmented reality (VR and AR).

Solutions


Compressive Accommodation Displays

https://www.youtube.com/watch?v=x5XS4-hFgCs
http://web.media.mit.edu/~gordonw/Focus3D/Focus3D.pdf

Stereo display

http://bankslab.berkeley.edu/publications/Files/stereo_display_prototype04.pdf

Comfort zone

external image stereo-comfort-zone-a.jpg
external image comfort.jpg