1. INTRODUCTION
Imagine yourself being a intelligent, motivated, and working person in the fiercely competitive market of information technology, but just one problem You can't use your hands. Or you can't speak. How do you do your job? How do you stay employed? You can, because of a very good gift from computer Industry : The Eyegaze, a communication & control system you run with your eyes.The Eyegaze System is a direct-select vision-controlled communication and control system. It was developed in
2.Who's using the Eyegaze System?
This system is mainly developed for those who lack the use of their hands or voice. Only requirements to operate the Eyegaze are control of at least one eye with good vision & ability to keep head fairly still. Eyegaze Systems are in use around the world. Its users are adults and children with cerebral palsy, spinal cord injuries, brain injuries, ALS, multiple sclerosis, brainstem strokes, muscular dystrophy, and Werdnig‑Hoffman syndrome. Eyegaze Systems are being used in homes, offices, schools, hospitals, and long‑term care facilities. By looking at control keys displayed on a screen, a person can synthesize speech, control his environment (lights, appliances, etc.), type, operate a telephone, run computer software, operate a computer mouse, and access the Internet and e-mail. Eyegaze Systems are being used to write books, attend school and enhance the quality of life of people with disabilities all over the world.
2.1The skills needed by the user :
2.1.1 Good control of one eye : The user must be able to look up, down, left and right. He must be able to fix his gaze on all areas of a 15-inch screen that is about 24 inches in front of his face. He must be able to focus on one spot for at least 1/2 second.
· Several common eye movement problems may interfere with Eyegaze use. These include:
Nystagmus (constant, involuntary movement of the eyeball):
The user may not be able to fix his gaze long enough to make eyegaze selections.
Alternating strabismus (eyes cannot be directed to the same object, either one deviates):
The Eyegaze System is constantly tracking the same single eye. If, for example, a user with alternating strabismus is operating the Eyegaze System with the right eye, and that eye begins to deviate, the left eye will take over and focus on the screen. The Eyegaze camera, however, will continue to take pictures of the right eye, and the System will not be able to determine where the user's left eye is focused. When the left eye deviates and the right eye is again fixed on the screen the Eyegaze System will resume predicting the gazepoint. Putting a partial eye patch over the nasal side of the eye not being observed by the camera often solves this tracking problem. Since only the unpatched eye can the screen, it will continuously focus on the screen. By applying only a nasal-side patch to the other eye, the user will retain peripheral vision on that side.
2.1.2 Adequate vision:
Several common vision problems may affect a user's ability to see text clearly on the Eyegaze monitor. These include the following:
Inadequate Visual acuity:
The user must be able to see text on the screen clearly. If, prior to his injury or the onset of his illness he wore glasses, he may need corrective lenses to operate the Eyegaze System. If he's over 40 years old and has not had his vision checked recently, he might need reading glasses in order to see the screen clearly.
In most cases, eyetracking works well with glasses. The calibration procedure accommodates for the refractive properties of most lenses. Hard-line bifocals can be a problem if the lens boundary splits the image of the pupil, making it difficult for the system's image processing software to determine the pupil center accurately. Graded bifocals, however, typically do not interfere with eyetracking.
Soft contact lenses that cover all or most of the cornea generally work well with the Eyegaze System. The corneal reflection is obtained from the contact lens surface rather than the cornea itself. Small, hard contacts can interfere, if the lens moves around considerably on the cornea and causes the corneal reflection to move across the discontinuity between the contact lens and the cornea.
Diplopia (double vision):
Diplopia may be the result of an injury to the brain, or a side effect of many commonly prescribed medications, and may make it difficult for the user to fix his gaze on a given point. Partially patching the eye not being tracked may alleviate double vision during Eyegaze System operation.
Blurred vision:
Another occurrence associated with some brain injuries, as well as a side effect of medications, a blurred image on the screen decreases the accuracy of eye fixations.
Cataracts (clouding of the lens of the eye):
If a cataract has formed on the portion of the lens that covers the pupil, it may prevent light from passing through the pupil to reflect off the retina. Without a good retinal reflection the Eyegaze System cannot accurately predict the user's eye fixations. The clouded lens may also make it difficult for a user to see text on the screen clearly. Surgical removal of the cataracts will normally solve the problem and make Eyegaze use possible.
Homonymous hemianopsia (blindness or defective vision in the right or left halves of the visual fields of both eyes):
This may make calibration almost impossible if the user cannot see calibration points on one side of the screen.
2.2 Ability to maintain a position in front of the Eyegaze monitor:
It is generally easiest to run the System from an upright, seated position, with the head centered in front of the Eyegaze monitor. However the Eyegaze System can be operated from a semi-reclined position if necessary.
Continuous, uncontrolled head movement can make Eyegaze operation difficult, since the Eyegaze System must relocate the eye each time the user moves away from the camera's field of view and then returns. Even though the System's eye search is completed in just a second or two, it will be more tiring for a user with constant head movement to operate the System.
1. Absence of medication side effects that affect Eyegaze operation:
Many commonly prescribed medications have potential side effects that can make it difficult to operate Eyegaze. Anticonvulsants (seizure drugs) can cause: nystagmus, blurred vision, diplopia, dizziness, drowsiness, headache and confusion. Some antidepressants can cause blurred vision and mydriasis ( abnormally dilated pupil.) And Baclofen, a drug commonly used to decrease muscle spasms, can cause dizziness, drowsiness, headache, disorientation, blurred vision and mydriasis. Mydriasis can be severe enough to block eyetracking. If the retinal reflection is extremely bright, and the corneal reflection is sitting on top of a big, bright pupil, the corneal reflection may be indistinguishable and therefore unreadable by the computer.
2.3.1 Cognition:
Cognitive level may be difficult to assess in someone who is locked in, especially if a rudimentary communication system has not been established. In general, a user with average intelligence will best maximize the capabilities of an Eyegaze System.
2.3.2 Ability to read:
At present, the Eyegaze System is configured for users who are literate. The System is text-based. A young child with average intelligence may not be reading yet, but probably has the capability to learn to read at an average age. He may be able to recognize words, and may be moving his eyes in a left to right pattern in preparation for reading. As an interim solution many teachers and parents stick pictures directly onto the screen. When the child looks at the picture he activates the Eyegaze key that is located directly underneath it.
2.3.3 Memory:
Memory deficits are a particular concern in considering the Eyegaze System for someone with a brain injury. A user who can't remember from one day to the next how to operate the system may find it too difficult to use effectively.
3. How does the Eyegaze System work?
As a user sits in front of the Eyegaze monitor, a specialized video camera mounted below the monitor observes one of the user's eyes. Sophisticated image‑ processing software in the Eyegaze System's computer continually analyzes the video image of the eye and determines where the user is looking on the screen. Nothing is attached to the user's head or body.In detail the procedure can be described as follows: The Eyegaze System uses the pupil-center/corneal-reflection method to determine where the user is looking on the screen. An infrared-sensitive video camera, mounted beneath the System's monitor, takes 60 pictures per second of the user's eye. A low power, infrared light emitting diode (LED), mounted in the center of the camera's lens illuminates the eye. The LED reflects a small bit of light off the surface of the eye's cornea. The light also shines through the pupil and reflects off of the retina, the back surface of the eye, and causes the pupil to appear white. The bright-pupil effect enhances the camera's image of the pupil and makes it easier for the image processing functions to locate the center of the pupil. The computer calculates the person's gazepoint, i.e., the coordinates of where he is looking on the screen, based on the relative positions of the pupil center and corneal reflection within the video image of the eye. Typically the Eyegaze System predicts the gazepoint with an average accuracy of a quarter inch or better.
Prior to operating the eyetracking applications, the Eyegaze System must learn several physiological properties of a user's eye in order to be able to project his gazepoint accurately. The system learns these properties by performing a calibration procedure. The user calibrates the system by fixing his gaze on a small yellow circle displayed on the screen, and following it as it moves around the screen. The calibration procedure usually takes about 15 seconds, and the user does not need to recalibrate if he moves away from the Eyegaze System and returns later.
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