Near point of Convergence:
Near point of convergence is the distance from the spectacle plane to the point at which the eyes can no longer converge or turn in. In lay terms, how well one can cross their eyes. Vergel™ has several stimuli which serve as targets for the subject to watch and report when they see "double".
The Near point of Convergence (NPC) is an extremely important measurement in binocular vision. The findings are essential in the evaluation of reading comfort, concussion and the various types traumatic brain injury (TBI). Although there is some debate as to what the minimum acceptable NPC is, most would agree that 5cm for break and 7cm for recovery are normal.
The stimulus for convergence may need to be simple for one subject and entertaining for the next. Therefore, Vergel was designed for both by including the following stimuli for convergence.
1) A simple 8 pt. black X on a white background.
2) A tri-colored led that changes color, as it get closer to the subject to keep interest.
3) A Worth 4 dot pattern of LED's to monitor and test suppression.
4) A single red colored led.
5) Optional Feature: Vectograghic near point fixation disparity target, to be used with polarized glasses.
In the evaluation of concussion/mtbi and traumatic brain injury, one of the most significant findings is a change in the NPC. Although it is useful to compare a concussion suspect or tbi patient to normals, it is much more important to compare the pre and post concussion findings to the subject's own baseline. This makes the base- lining of athletes with Vergel™ an invaluable tool in the in the diagnosis of concussion and TBI, especially an athlete.
Recent research suggests the most sensitive test for concussion may be a near point fixation disparity test. This test requires accurate, multiple dynamic measurements for which Vergel™ is perfectly suited.
Near Point of Accommodation
The near point of accommodation (NPA) is a measurement of how close one can bring a object or text (usually 20/40 or 20/30) before it blurs. This is also measured from the spectacle plane to the text or object. Vergel has two rows of print, one 20/40 and the other 20/30 in the middle of his face to serve as a target for accommodation.
Focusing ability varies with age so one needs to compare an individual to the norms for his or her age, utilizing the table provided. But, as with NPC, when evaluating an individual suspect of head injury or concussion, it is always better to compare him or her to themselves by having taken a baseline measurement.
Vergel™ also come with an auditory stimulus (STNS Sound Button) that may be toggled on or off to provide an auditory clue and biofeedback stimulation. This is particularly useful in the training function of the device
The device requires a 9V battery. *Note: When the device is not be used for a period of one minute Vergel will automatically shut down to save energy. To reset Vergel at any time, simply turn it off then back on.