what follows describes the preferred embodiment of our system but does not in any way limit the myriad of ways our system and its components can be modified , upgraded or altered without violating its form or function . it would be impossible to fully and completely convey all the variations in a few pages of text and diagrams but anyone skilled in the arts would readily recognized the possibilities inherent in our system . our system relies on proprietary , clinically validated systems integration among various components consisting of two primary parts : 1 ) internet - based software that is deployable via the internet or on electronic media such as compact discs . 2 ) computer system with a cpu , storage device , viewing surface , browser interface , and input device such as a keyboard , mouse , or trigger switch . in detail , fig1 outlines the basic steps involved during visual field testing with our system . the software is easily downloading via the internet from a server or can be directly transferred to the computer system on an electronic media . once the software is launched and the test subject or subjects are presented with a brief instructional session to the test subject or subjects prior to testing on the display screen that is connected to the computer system . this display screen can be of any light emitting or light reflecting surface such as a cathode ray tube , lcd monitor , or even a wall or screen ( light reflecting surface ) onto which a video projection system illuminates the area . the option to display on a large screen the size of a movie theater confers for a unique feature to this system whereby a large number of subjects can be tested simultaneously simply by having multiple subject view the same large screen . each subject would have an input device to respond the stimuli presented on the screen . because the screen size is large , there would be an insignificant difference in the angular viewing angle when multiple subjects are clustered centrally with respect to the screen . the software automatically adjusts all the parameters of the test such as the location of the blind spot , fixation spot , the stimuli location without any input from the test subject . only the contrast level of the monitor needs adjustment by the test subject by using a relative gray - scale grid presented on the display screen . the use of a gray scale rather than color variation facilitates greater standardization among the numerous types of monitor available . a gray scale is characterized by equal inputs of red , green , and blue . the only variance is luminance . each primary color as well as hue , saturation , and luminance is adjusted on a scale of 0 - 255 in customary 8 - bit system . at the extremes of “ black ” and “ white ” the luminance as well as the 3 primary colors varies from 0 to 255 , respectively . by eliminating individual variations in each of the 3 primary colors that would be needed to produce various shades of orange or brown for instance , there is less propensity for marked , individual variation among monitors . using a relative rather than absolute scale further reduces variation in the testing parameters . besides the technical aspects of why a relative gray value scale is optimal for visual field testing , perhaps the most important is that it has been clinically validated with a patient trial comparing it to the gold standard for automated visual field testing , the humphrey visual field analyzer . the following steps proceed in logical order from position the test subject at the appropriate distance away from the viewing screen to initiation of the actual visual field screening test when the stimuli are repeated presented until the visual field is mapped and analyzed . proper position of a test subject from the testing screen is crucial for the reliability and performance of any perimetry system . in our system , positioning can either be done with a preset ruler or marker for that specific screen size and desired breadth of visual field examination . this distance value is easily calculated by those skilled in the arts as half the viewable horizontal screen size divided by the tangent of 25 °, given the fact that the preferred embodiment our system tests 25 ° of visual field away from fixation horizontally . another method of positioning , shown in fig2 , involves the use of the blind spot , which is the preferred embodiment of our system since this technique requires no additional accessories . it is known that the blind spot 2 ( right eye ), is situated 15 ° temporal to fixation ( 1 ) ( edme mariotte : nouvelle découvverte touchant la veüe . a paris chez frederic leonard , mdclxviii . ), and the size of the blind spot measures 40 horizontally and 6 ° vertically about its center . the blind spot exists because physiologically , the optic nerve lies in this area . objects or images falling within this area will not be detected . however there is no noticeable gap or hole in the visual field around this area because of a phenomenon known as “ fill - in ” effect in which the brain “ fills ” in the missing area without conscious input or knowledge . if a test subject , with one eye covered and the other focusing on the fixation point , slowly moves in from a position approximately 1 . 5 times the horizontal dimension of the screen size towards the screen , there will be a point where the entire blind spot mark “ disappears ” from view . at this point , the test subject is correctly positioned . although not evident from the diagram , the blind spot mark flashes continuously on the screen . this enables to test subject to automatically adjust positioning if the blind spot mark appears again . the blind spot will also reappear if the test subject does not focus on the fixation spot . we have also developed another novel method of positioning , as shown in fig3 , that not only relies on the principle of blind spot location , which is well known in the arts , but also takes advantage of the “ fill - in ” effect described earlier . in this method , as the test subject slowly moves in from a distance approximately 1 . 5 times the horizontal dimension of the screen size towards the screen while focusing on the fixation spot ( 1 ), the discontinuous line ( 3 ) suddenly becomes a continuous one as the central circle ( 3 ) corresponding to the blind spot disappears from view . using this positioning method , there are now two cues to prompt the test subject to adjust positioning if necessary , the re - emergence of the blind spot mark or the reappearance of a discontinuous line . moreover with this novel method , there is now a constant , visible marker delineating to the test subject that there is proper positioning . the embodiment of how our system performs the tasks of visual field testing will become clear from the following description of fig3 . fig4 embodies the form and function of our system but in no way captures the entire essences of it as there can be numerous iteration of our system without altering the foundation of our system . as shown , there is a central fixation spot ( 1 ) with blind spot markers ( 2 ). not shown is the fact that the blind spot marker continuously flashes throughout the test to aid in the proper positioning of the test subject as described previously . also shown are different luminance levels the stimuli ( 4 , 5 , 6 ) that are intermittently presented throughout the test . by varying the luminance of the stimuli , the depth of visual field defects can be assessed . the preferred embodiment of our system uses three difference luminance levels for screening to detect between mild , moderate , and severe levels of visual field defect depending on which of the luminance level was missed during testing . throughout the test , there are also reliability parameters consisting of false positive , false negative , and fixation loss . these parameters are crucial to determining how accurately and reliably the test subject performed on the test . although not directly shown in fig3 but well known in the arts , our system registers a false positive whenever a test subject responds with a click when there was no stimulus displayed on the screen and conversely , a false negative occurs whenever a test subject fails to respond the highest luminance level at the same location where a lower luminance level was detected earlier . fixation loss is calculated by displaying the highest luminance stimuli ( 7 ) in the area of the blind spot . recognition of this stimulus is indicative of improper fixation on the fixation spot . it should be evident that our system is able to carry out more detailed , quantitative examination of the visual field than with just a few luminance levels and it is also obvious that the degrees of visual capable of being test is not limited to 20 - 25 ° but is in fact much greater or smaller than this simply by adjusting the positions of the different markers and stimuli presented . fig5 details the algorithmic method used to assess visual motor reflex at any point in the visual field . the measurement of visual motor reflex is best done a brief rest following visual field examination or alternatively in can also be done during the visual field test . by utilizing the reliability parameters previously described for visual field screening , the reliability of the visual motor reflex examination can also be gauged . the algorithm entails testing points the visual field that have previously been shown on visual field examination to be normal in each of the four quadrants of the visual filed . the number of points tested in each quadrant can be varied according to the required degree of sophistication required . the response time is calculated as the interval between stimuli presentation and stimuli acknowledgement . the stimulus can be visual or auditory depending on the capability of the local system . the results from visual motor reflex testing can then be displayed in a tabular or graphical format . from the previous detailed description of the embodiment of our system ,
an automated unaided virtual perimetry system and underlying method for relative - threshold contrast sensitivity interrogation of the visual field via algorithmic presentation of visual stimuli on a screen and subsequent analysis of test response data for the detection of pathophysiologic scotomas as well response time registration and analysis for visual motor reflex testing . launch of system via access from a remote server or direct installation of systems technology allows seamless capability at the local computer system to instruct , administer , and analyze output of stimuli and input of responses of test subjects or subjects independent of external input or control . specific algorithmic test environment is designed to achieve comparable clinical efficacy and diagnostic utility to office - based perimetry system .