Patent Document:

referring to the figure of drawing , a flow diagram of a device designed in accordance with the invention is shown . this device comprises a substantially hemispherically shaped screen 1 referred to as a perimeter bowl for displaying the light targets . the patient &# 39 ; s head is placed in position within the bowl on a frame which minimizes head movement during the test . the patient is positioned so that eye level is even with fixation light 3 in the center of the screen . during a test , the patient &# 39 ; s eye must fixate on the fixation light to insure an accurate test . fixation monitor 5 is provided to observe the fixation status of the patient at set intervals , e . g ., every 1 / 4 second , and to transmit a signal to the central control means 7 when the fixation status deviates beyond a predetermined point . the fixation monitor observes fixation status by known techniques , such as directing infra - red light at the eye which reflects off the concave surface of the cornea and back to the monitor where photocells record the intensity and location of light and compares these values to a fixation norm . if the observed values deviate from the norm for complete fixation beyond a predetermined amount , the monitor transmits this information to the central control means . central control means 7 is a micro - processor which is programmed to transmit and receive the signals necessary to control the various parts of the device and to receive and record the patient &# 39 ; s responses and lack of responses . the central control means is responsive to auxiliary control means 9 which is operated by the physician or technician . the auxiliary control means is most preferably an x - y pad which is a commercially available device used to place information into a computer . the x - y pad generates data that corresponds to the x and y co - ordinates of any given point on the pad . the x - y pad allows the operator to test any desired point on the visual field chart . a visual field chart is placed over the pad and by manually positioning a marker at any point on the chart , the exact position of the marker is transmitted to the central control means as x and y co - ordinate data . the central control means interprets this data and transmits the appropriate mirror position data to the servo - controlled mirror 11 . the auxiliary control means also includes means for enabling the operator to adjust the size , intensity and / or color of the light target . dials or keyboards are exemplary of such means . the dial or keyboard transmits a signal to the central control means which interprets it and transmits the appropriate control signal to a shutter assembly which controls the size , intensity and color of the light target . because the operator completes the visual field chart on the x - y plotter of the auxiliary control means , there is no need for another visual field chart holder and stylus present in the device described in u . s . pat . no . 4 , 260 , 277 , although these items may be included to reproduce the test results . thus , with the exception of the auxiliary control means , the device of the invention is identical to that described in the aforesaid patent . it includes means 13 for projecting a light target onto the servo - controlled mirror . this includes the shutter assembly for controlling the size , intensity and color of the light target . the device of the invention also includes response means 15 for the patient to acknowledge vision . these various means are described in detail in u . s . pat . no . 4 , 260 , 277 , and that description will not be reproduced herein . however , it is understood that various modifications of the device can be made without departing from the spirit of the invention . for example , the device can be equipped with display means 17 which displays the target status , patient response status and fixation status for easy reference during a test . while the invention has now been described in terms of various preferred embodiments , those of skill in the art will recognize that numerous additions , substitutions , omissions and modifications can be made . it is , therefore , intended that the scope of the invention be solely limited by the claims which follow .

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