A completely computer-generated environment that uses a display (often head-mounted display) to immerse the user in the artificial environment. The sense of immersion is highly dependent on engaging the user's senses - vision, sound, and touch are most often stimulated, while taste and smell are often not addressed.
Developers of virtual reality games, design environments that a user can interact with to improve the immersion experience, and developers rely heavily on 3D images to trick the user's visual system that the environment is "real".
Vivid Vision’s VR activities work to reduce cortical suppression and to improve eye-teaming skills and 3D ability. The methods utilized within Vivid Vision’s software include dichoptic training and direct stereo training.
Typically, VR involves the utilization of both eyes working together to maximize an overall VR experience, but by adapting the unique software aspects of this technology, virtual reality is now incorporated into many vision therapy programs and helping patients with binocular vision dysfunction.
One primary application of VR in the treatment of amblyopia as a binocular rather than a monocular vision disorder. The premise of rehabilitation of the amblyopic system, therefore, would consist of a reduction of cortical suppression while simultaneously strengthening fusion. This objective can be done by combining features common in vision therapy, perceptual learning, and anti suppression, in an immersive virtual reality environment
Video gameplay has been shown to improve visual attention and visual processing through training-induced learning. It seems that action games that are engaging, fast-paced, and require monitoring of multiple objects are more effective in producing these changes.
Incorporating in gameplay, a dichoptic stimuli presentation (differential image rendering of visual stimuli for each eye independently), simultaneous perception occurs where the amblyopic visual system is forced to use both eyes together in order to successfully complete the task.
Recent advances in VR hardware have removed barriers, such as large, heavy equipment and cost, from being used in visual rehabilitation. Medical technology companies are now using a combination of dichoptic image presentation and perceptual learning to treat various binocular vision disorders. This treatment method demonstrates improvements in both visual acuity and stereoacuity.
Stereoscopic displays, such as 3D televisions and VR headsets, create an interesting conflict to a binocular system. Under normal viewing conditions, convergence and accommodation work in sync to position the eyes on a target.
The vergence-accommodative system adjusts as a stimulus moves closer or farther away. In VR, there is a relative disconnect between these systems: accommodation is fixed on a single plane, whereas vergence demand is constantly altered. It has been established that these two systems can be dissociated; vision therapy programs for nonstrabismic disorders, such as CI and accommodative dysfunction, often work these systems in isolation as well as in combination, with the ultimate goal of automaticity and flexibility of vergence and accommodation.
Vergence demand in VR may be affected by stimuli, such as a ball, moving closer to the user within the scene. Alternatively, the entire scene can be adjusted to mimic the effects of ophthalmic prisms. Adjusting the entire visual scene inward for one or both eyes has an effect similar to viewing the scene, unaltered, through base-out prismatic lenses.
Vision therapy programs that focus on enhancing patients’ fusional ability and accommodative flexibility have been shown to normalize convergent fusion reserves near the point of convergence. The outcome is a normalization of binocular and accommodation abilities with reduction of symptoms in cases of CI.
The high plus lenses are aspheric to decrease optical aberration. Fresnel prisms are often used to decrease the thickness of the lens to afford more room for glasses or eyelashes and to increase the field of view.
The size of the screen and resolution are factors in determining the pixel density per inch (PPI). A low PPI can cause a screen-door effect due to the magnification of the pixels. The displays within an HMD are greater than 500 PPI. At the distance viewed within the headset, most people can perceive up to 2000 PPI.
The mainboard contains various sensors, such as an accelerometer, gyroscope, and head tracking, to adjust the virtual environment so that it mimics the real environment. Besides allowing a more immersive experience, these sensors are important to reduce VR sickness.
Eye-tracking headsets may afford clinicians cost-effective means to test and assess oculomotor function as well as allow adaptation for oculomotor rehabilitation. Eye-tracking headsets will allow objective measurements without user input.
With processing software located in the device itself, all-in-one headsets provide flexibility and the ability to not be tethered to a computer. Demand for VR as a home vision therapy program has increased, also used as follow-up and maintenance therapy, and continuity of patient care.
All-in-one headset units are not only being used by patients for at-home vision therapy but are also helping decrease the gap between urban to rural populations, reducing drive time to appointments, and offer vision therapy at lower patient cost.
As this "all-in-one" technology evolves, there is now the ability to cast the scene viewed inside the headset by the means of an adaptive cable to an external monitor or other display.