In the real life setting our eyes must do two things:
- The eyes must 'verge', meaning rotate slightly inward or outward to project the image at the center of both retinas.
- The eyes must 'accommodate', which means to change the focal power of the lens in both eyes to maintain a clear image.
In a natural, real life setting the retina in each eye forms a two-dimensional image of our surroundings and our brain processes these two images into one 3D visual experience. This 3D perception is also known as depth-perception.
Artificial 3D, such as in movies or with gaming devices, causes viewers to focus where the light is emitting from the screen which is at one distance, but verge where the 3D object appears to be in space which is a different distance. In other words, the eyes must remain focused on the display, but must converge at the depth (either in front of or behind the display) where the image from each eye overlaps. This is referred to as the vergenceaccommodation conflict. The vergence-accommodation conflict becomes more noticeable on smaller screens and low quality content with less attention to detail.
Artificial 3D is generated by using a special projector to display two images on the screen. The two images are the same; however, they are filmed or drawn from slightly different angles. 3D technology tricks the brain by showing the left eye one image and the right eye another image. The brain layers these images together to produce a 3D image. The illusion of three dimensions occurs when the two images travel to the visual cortex, the area of the brain primarily responsible for processing vision, and are correlated into one pop-out or 3- dimensional image.
Although artificial 3D technology has been around for more than a century, it has net yet gained widespread use. The entertainment industry is applying 3D vision techniques to movies, television and video games. 3D technology also has a promising future in specialized 3D applications in surgery, computer design, and classroom education.
As 3D technology is developing and gaining accessibility among consumers, associated vision problems are being identified. The vision symptoms associated with 3D viewing include:
- Blurred vision
- Dizziness
- Double vision
- Eyestrain
- Headaches
- Nausea
Some 3D vision experts are referring to this group of symptoms as 3D Vision Syndrome, although no formal or recognized classification has been made official. 3D symptoms are thought to be the result of a greater sense of immersion than 2D viewing. In a recent study, 21% of participants reported symptoms while watching a movie in 3D. The symptoms were more frequent and more severe among younger participants; and many 3D vision symptoms were more prevalent among individuals with amblyopia (clarity of vision is typically much better in one eye that the other) and strabismus (when an eye is turned in, out, up or down). Both amblyopia and strabismus can disrupt and impede the 3D viewing process. There are also other vision problems that detract from the 3D viewing experience such as convergence insufficiency, convergence excess, divergence problems, and accommodative or focusing problems.
Individuals who have vision conditions such as amblyopia (an imbalance in visual strength between the two eyes), strabismus (misaligned eyes), or other conditions that persistently inhibit focusing, depth perception or normal 3D vision, will have difficulty seeing artificial, digital 3D images. It is estimated that as many as 3 to 9 million people in the United States have vision problems that inhibit their ability to properly see and enjoy artificial, digital 3D images. And as many as 56% of people between 18 and 38 years of age suffer from symptoms related to depth-perception problems.
In order to have proper depth-perception and perceive 3D an individual must have:
- Accommodation – lenses in the eyes must change shape and maintain clear focus as objects move.
- Aerial perspective – the ability to perceive contrast differences between nearby objects versus distant objects.
- Parallax – perceive differences as the head moves from side to side, closer objects appear to move more than distant objects.
- Size familiarity – the ability to tell how far away an object is based on how large or how small it looks.
- Stereoscopic (binocular) vision – the two eyes provide slightly separate images to produce the perception of depth and 3 dimensional structure.
Problems viewing 3D has to do with binocular vision, the ability to align both eyes on a target and combine the visual images from the two eyes into one single, three-dimensional perception. 3D is our ability to judge distances; to be aware of our position in space.
At this time there are no conclusive studies regarding either the short-term or the long-term effects of 3D digital devices and products on the eye, visual development, health or function in children. However, Nintendo and several other 3D device companies have issued warnings about children's use of their products. The warnings urge parents to prevent prolonged viewing of the device's digital images by children under 6 years of age.
Some experts view 3D movies and devices as screening tools for binocular vision problems. If an individual can't see 3D or experiences any of the symptoms listed above, this is a good indication that they may have a binocular vision problem. A binocular vision problem is not like a cut, scrape or sprained ankle. As a parent you can't “see” the problem; and your child won't realize they have poor depth-perception because they've always seen the world without 3D vision.
Binocular vision problems, such as lack of depth-perception, is the inability to effectively perceive visual space. The symptoms below are a few of the ways binocular vision problems can be observed:
- Being clumsy or bumping into objects
- Difficulty throwing or catching a ball
- Difficulty with balance
- Difficulty with coordination
- Difficulty judging distance when driving
It is important to note that individuals do not “outgrow” binocular vision problems.
A comprehensive eye examination and binocular vision assessment is recommended for anyone who has 3D vision problems, and is the only way to accurately determine the cause. Vision screenings at school or the pediatricians' office are not a substitute for comprehensive eye examinations that detect and diagnose these vision problems. The solution can be as simple as a pair of glasses or a treatment program of vision therapy. Binocular vision problems can be successfully treated.