Evoked potential autorefractometry system
First Claim
1. An evoked potential autorefractometry system for a patient, comprising:
- stimulus production means for producing an alternating steady-state stimulus pattern;
a continuously variable focus lens projecting the stimulus pattern directly to the patient with a continuously changing focus and providing a fixed distance from the pattern to said lens;
evoked potential sensing means for sensing evoked potentials produced by the patient; and
control and determination means for determining the maximum amplitude of the evoked potentials, produced by the patient as the focus of the lens is continuously changed, by narrow band asychronous filtering the evoked potentials and detecting amplitude peaks of the evoked potentials.
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Accused Products
Abstract
An evoked potential autorefractometry system includes a computer driving an alternating checkerboard mirror stimulus to project a stimulus pattern directly to a patient through a continuously variable focus lens controlled by the computer and which maintains a constant image size on the patient'"'"'s retina. The evoked potentials produced by the patient are amplified, asychronously filtered both in an analog and digital fashion to allow peak to peak detection of the evoked potentials to determine amplitude. The digital filter includes a 255 point running sum. The peak to peak amplitudes are asychronously digitally filtered using a 16 point running sum to produce an amplitude measure of the evoked potentials. The lens is swept rapidly from one extreme of focus to the other extreme in relatively large steps to determine the area in which the peak amplitude occurs. The lens is then subsequently swept in smaller and smaller range sweeps using smaller and smaller steps around the peak amplitude until the peak in the amplitude is pinpointed within a desired diopter at which point the lens position is printed out on the printer as the patient'"'"'s prescription.
73 Citations
41 Claims
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1. An evoked potential autorefractometry system for a patient, comprising:
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stimulus production means for producing an alternating steady-state stimulus pattern; a continuously variable focus lens projecting the stimulus pattern directly to the patient with a continuously changing focus and providing a fixed distance from the pattern to said lens; evoked potential sensing means for sensing evoked potentials produced by the patient; and control and determination means for determining the maximum amplitude of the evoked potentials, produced by the patient as the focus of the lens is continuously changed, by narrow band asychronous filtering the evoked potentials and detecting amplitude peaks of the evoked potentials. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. An evoked potential autorefractometry system for prescribing a lens for a patient, said system comprising:
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a square wave generator generating a square wave of 2.4 kilohertz; a stimulus stepper motor and stimulus stepper motor control circuit, operatively connected to said square wave generator, turning said stimulus stepper motor at 3 hertz in dependence upon the square wave; a stimulus generator including a checkerboard mirror and a light chopper wheel connected to said stimulus stepper motor, said light chopper wheel causing light to be alternately reflected from the checkerboard mirror toward the patient or transmitted through the checkerboard mirror toward the patient producing an alternating steady state stimulus pattern; a continuously variable focus lens projecting the light from the stimulus generator to the patient while maintaining a constant image size and providing a fixed distance from the checkboard mirror to said lens; an electoencephalographic cap having selfpreparing electrodes adapted to receive the evoked potentials produced by the patient in response to the light from said stimulus generator; a shielded wiring system operatively connected to the self-preparing electrodes of said cap; a shielded narrow bandwidth high gain amplifier operatively connected to said shielded wiring system; a narrow bandwidth filter, operatively connected to said stepper motor control circuit and said narrow bandwidth high gain amplifier, filtering the evoked potentials; a digital-to-analog converter, operatively connected to said narrow bandwidth filter, convering the filtered evoked potentials into digital values; a computer, operatively connected to said digital-to-analog converter, asychronously digitally filtering the digital values using a first running sum technique, detecting the amplitude peaks of the first running sum, to digitally filtering the peaks using a second running sum technique, determining the maximum value of the digitally filtered peaks, storing a lens position of said continuously variable focus lens coincident with said maximum and producing lens position control signals; and a lens position control circuit and lens stepper motor, operatively connected to said computer and coupled to said continuously variable focus lens, controlling the position of said continuously variable focus lens in dependence upon the lens position control signals. - View Dependent Claims (33, 34)
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35. A method for determining visual acuity, comprising:
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a. stimulating a patient with an alternating steadystate stimulus pattern directly through a continuosly focusable constant image size lens; b. continuously changing the focus of the lens while maintaining a fixed distance between the lens and the pattern; c. detecting evoked potentials produced by the patient; d. asychronously filtering the evoked potentials; e. detecting the maximum amplitude of the evoked potentials as the focus of the lens is changed; and f. storing the lens position of the maximum amplitude. - View Dependent Claims (36, 37)
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38. A continously variable focus lens system receiving a stimulus and transmitting the stimulus to a patient in an evoked potential autorefractometry system, said system comprising:
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a fixed diopter lens receiving the stimulus while maintaining a fixed stimulus to lens distance; a focusable telescope, coupled to said fixed diopter lens, transmitting the stimulus to the patient; and focus means, coupled to said focusable telescope, for continuously changing the focus of said focusable telescope. - View Dependent Claims (39, 40, 41)
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Specification