Abstract: A field test apparatus and method is disclosed in which gradual movement of the head supporting chin cup is used to maintain a centered relation between the eye being tested and the trial lens frame holding the required prescription for optimum vision of the patient. During the test, alternating illumination is provided in the infrared between a central corneal reflection and an iris illuminating source which imparts a high contrast bright circular iris image surrounding a central dark pupil. Content addressable memories are used to delineate areas of contrast change for rapid and abbreviated microprocessor analysis of conventional RAM images. Both the corneal reflection image--which is a brightly illuminated spot on an otherwise dark background--and the pupillary image--which is a dark pupil surrounded by a brightly illuminated high contrast image of the iris are approximately located at their boundaries using content addressable memory.

Abstract: A pressure measurement system includes a diaphragm and a chamber for exposing one side of the diaphragm to a fluid. A force transducer is provided for measuring force exerted by the fluid on the one side of the diaphragm independent of diaphragm position. A ferromagnetic plate is attached to the diaphragm to enable removable coupling of the diaphragm with a magnet permanently attached to the force transducer.

Abstract: A method of generating wave forms for a phaco surgical handpiece, with each wave form having a different frequency includes storing a plurality of sets of digital information, each set corresponding to a different specific frequency and selecting a set of digital information in response to an input corresponding to a resonance frequency of said phaco surgical handpiece. Thereafter selected digital information is read in a manner producing a digital output having a corresponding frequency equal to or lower than the frequency corresponding to the selected set of digital information. Subsequently, the digital output is converted into an analog wave form for driving said phaco surgical handpiece.

Abstract: A field test apparatus is disclosed which is interactive both in the automated positioning of trial lenses (used to correct the patient's focal distance to the tester hemispherical projection screen) as well as providing automatic gaze direction determination through automated video surveillance of the patient's eye. A moveable trial lens holder is provided. This trial lens holder is remotely moveable horizontally and vertically and carries light sources for illuminating the eye preferably in the infrared spectrum at oblique angles preferably towards the center of the eye from the periphery of the trial lens holder. In the gaze direction determination system, a gaze direction determination infrared source--preferably on the surface of the screen near the center of the screen--generates a gaze direction determination reflection on the cornea of the eye--this reflection being near the apex of a normal spherical cornea.

Abstract: A digitial electronic foot pedal control system, especially for medical apparatus and the like having a plurality of operating functions which can be selected among, comprises a pivotally mounted pedal shaft and a foot-operated pedal fixed to the shaft to pivot therewith. Included are a shaft encoder connected to the shaft for producing a digital shaft position output signal indicative of pedal shaft position relative to a reference position and a plurality of address cards each having N addresses corresponding to N given shaft positions. Each address card corresponds to one or more medical apparatus functions and is selected when a corresponding function or functions are selected, each of the addresses on each address card corresponding to a particular shaft rotational position and each storing a given set of control output signals for operating the corresponding function or functions.

Abstract: A phacoemulsification probe for ultrasound removal of an eye lens (for example a lens having a cataract) is provided with a safety circuit for prevention of shock to the patient. The probe includes a piezoelectric sound transducer electrically powered with over 200 volts (RMS) at 50 kHz. This voltage, if improperly grounded, can be life threatening when the probe is used in the vicinity of the optic nerve. According to the improvement, the probe is provided with at least two discrete grounded paths. The power supply to the probe is enabled by a comparator testing a small current to ground through at least one and preferably both ground wires. When the existence of at least one ground path is verified and power to the probe is thus enabled, ground return from the probe flows through the paired grounded wires. This flow to ground is compared for precisely equal flows. Where non-equal flow of current to ground occurs, power to the probe is immediately interrupted.

Abstract: In an eye field tester, a vidicon camera observes the eye being tested and relays the resultant low light level image to the periphery of a digital display. The digital display contains both an image of the eye on the periphery and the plot of the visual field of the eye under test in the center. The vidicon observing the position of the eye has its horizontal and vertical sync pulses software generated to presettable counters. These counters generate corresponding delayed horizontal sync and vertical sync pulses for the vidicon. As a result of the delayed sync pulses, the central eye image of the vidicon is offset to the periphery of the digital screen (typically to the upper left-hand portion thereof). The offset image is gated into character spaces on the digital screen utilizing software generated character attribute.

Abstract: In an eye field tester, a vidicon camera observes the eye being tested and relays the resultant low light level image to the periphery of a digital display. The digital display contains both an image of the eye on the periphery and the plot of the visual field of the eye under test in the center. The vidicon observing the position of the eye has its horizontal and vertical sync pulses software generated to presettable counters. These counters generate corresponding delayed horizontal sync and vertical sync pulses for the vidicon. As a result of the delayed sync pulses, the central eye image of the vidicon is offset to the periphery of the digital screen (typically to the upper left-hand portion thereof). The offset image is gated into character spaces on the digital screen utilizing software generated character attribute.