The ForeseeHome® AMD Monitor uses a patented technology called Preferential Hyperacuity Perimetry (PHP).
Hyperacuity, or Vernier acuity, is the human ability to perceive minute differences in the relative spatial localization of two objects in space.
During a PHP test, stimuli are successively flashed in various locations of the visual field. A typical stimulus consists of a series of dots, the majority of which are aligned with respect to each other. A few dots are misaligned, creating the perception of a wave or distortion in an otherwise straight line. The brief presentation ensures that cortical completion is not engaged and that fixation is maintained during the entire presentation of each stimulus. The presentation of the signal is triggered when the patient is fixating on the center of the screen. The patient's task is to mark the location where the distortion was perceived. When the stimulus is projected on an unhealthy area of the retina, the patient may perceive two or more distortions on the line: one corresponding to the artificial wave and the other corresponding to the patient’s pathological distortion.
According to the preferential looking principle, when presented with several stimuli, the visual attention of a subject is automatically attracted to the more prominent source. Hence, if the pathological distortion is larger than the artificial wave, the patient is likely to ignore the artificial wave and mark only the location of the pathological distortion. This principle is employed not only to localize pathological distortions, but also to quantify their perceived size.
Based on the PHP quantification capabilities, Notal Vision, Ltd. designed a test with various amplitudes of artificial distortions that maximally distinguishes between dry AMD patients and newly diagnosed wet AMD. Numerous evaluations have demonstrated the technology’s keen ability to provide early detection of changes occurring within a patient’s vision, often before the patient is even aware.
The ForeseeHome AMD monitor is designed as a closed viewer for single eye examination. A set of lenses embedded within the viewer ensures that the test is viewed as if projected from infinity, such that a patient with good distance vision sees the test in maximal focus. The patient starts the test by inserting his/her head within the viewer. A pair of infrared sensors located in the walls of the viewer detects the position of the head relative to the hood, and ensures that the test is not presented until the head is correctly positioned. The tested eye may be alternated from left to right by half cycle rotation of the viewer.
Patients are instructed to test their prescribed eye(s) daily and their responses are automatically transmitted to the Notal Vision Data Monitoring Center (DMC) at the end of each test. The wireless communication technology facilitates fast and reliable transmission of data which is then made available to the physician through a secure website. Tests are continuously compared to a normative database threshold and the patient's own baseline. When a statistically significant change of test patterns is detected, the DMC alerts the clinic so that they can schedule a prompt clinical examination with the patient.
In addition to monitoring test scores, the frequency of use is also tracked. To encourage patients to test at an adequate frequency (i.e., one that will allow timely detection in a conversion event), the DMC will contact the patient if no results are received for seven consecutive days.