Abstract: A rebound tonometer is improved by providing a tilt signal from a tilt sensor of the rebound tonometer to a signal processor of the rebound tonometer, and configuring the signal processor to apply a tilt correction factor to a basic IOP measurement value calculated by the signal processor to provide a final IOP measurement value, wherein the tilt correction factor depends on a tilt direction and a degree of tilt indicated by the tilt signal. The final reported IOP measurement value takes into account gravitational effects on the probe due to tilt. As a result, measurements made at relatively small tilt angles are now usable, thereby improving efficiency. A corresponding rebound tonometry measurement method, and a method of calibrating a rebound tonometer for tilt correction, are also disclosed.

Abstract: A headrest for an ophthalmic instrument facilitates fine positioning of the instrument relative to an eye of a test subject without the need to remove a contact element of the headrest from contact with the test subject's face. The ophthalmic instrument may be, for example, a rebound tonometer or a non-contact tonometer. The headrest includes a hollow bulbous contact element formed of resiliently deformable material, for example a thermoplastic elastomer (TPE) or silicone rubber. An outer surface of the contact element may have a spherical shape or a spheroidal shape when the contact element is not deformed.

Abstract: A spatially compact, lightweight positioning system for guiding an operator in positioning an ophthalmic instrument relative to an eye of a test subject has first and second light sources and an area detector spaced apart from a measurement axis of the instrument and from each other for providing positioning images which may be evaluated relative to stored calibration image information to determine current position of the instrument relative to the eye. The first and second light sources may fit within a lateral distance less than or equal to 25 mm. First and second illumination axes associated with the light sources may reside in a horizontal plane containing the measurement axis, and an observation axis of the area detector may reside in a vertical plane containing the measurement axis. The light sources and the area detector may be intersected by a plane which is normal to the measurement axis.

Abstract: A docking station for receiving a hand-held rebound tonometer and a probe container carrying disposable tonometer probes has a docking cavity for receiving a portion of the rebound tonometer and a container receptacle for receiving the probe container. The docking station has an actuation feature arranged to move a cover associated with the probe container from a closed position to an open position as the container is inserted into the container receptacle so that tonometer probes in the container are accessible. The actuation feature may include a projection extending into an entryway leading to the container receptacle for engaging the cover but not the container, such that further insertion of the container moves the cover from the closed to the open position. The docking station may also have a storage recess for receiving an empty probe tube and cap after the probe has been removed from the tube for use.

Abstract: Viscoelastic properties of the cornea are derived from an ophthalmic measurement signal representing velocity as a function of time of a contact probe rebounded by the eye. The viscoelastic properties include a “Lost Energy Ratio” (LER), a “Time Shift” (TS), a damping parameter (?), and an elastic parameter (?). An improved method for determining intra-ocular pressure from the measurement signal is also disclosed, wherein a first derivative of the measurement signal at a moment in time when velocity of the probe is zero due to contact of the probe with the cornea is calculated and correlated to an intra-ocular pressure value.

Abstract: A changing force is applied to a cornea to cause a corneal deformation cycle. Signal information related to a corneal radius of curvature during the corneal deformation cycle is inverted and calibrated to an effective curvature defined as the inverse of the radius of curvature of the cornea. A dynamic relationship between the effective curvature of the cornea and the force applied to the cornea during the corneal deformation cycle is represented, and at least one biomechanical property of the corneal tissue, for example a bending modulus, is determined from the dynamic relationship.

Abstract: An ophthalmic instrument includes a carrier positionable relative to a test subject, and first and second measurement units mounted on the carrier by corresponding first and second parallelogram linkages. The first measurement unit, for example an autorefractor/keratometer, performs a first type of ophthalmic measurement, and is guided by the first parallelogram linkage to move relative to the carrier simultaneously in forward and downward directions from an idle position to a measurement position. The second measurement unit, for example a tonometer, performs a second type of ophthalmic measurement, and is guided by the second parallelogram linkage to move relative to the carrier simultaneously in forward and upward directions from an idle position to a measurement position. The first and second measurement units may each have a respective optical axis which aligns with a fixed measurement axis of the carrier when the measurement unit is in its measurement position.

Abstract: In an ophthalmic instrument that directs a fluid pulse at a cornea to cause reversible deformation of the cornea and monitors the corneal deformation to generate a deformation signal, the shape of the deformation signal is analyzed with respect to deformation signal data from a statistical population of eyes to calculate a deformation signal score indicating a degree of probability that the deformation signal corresponds in shape to a normal deformation signal for normal eyes in the population. In calculating the deformation signal score, significant geometrical signal parameters are calculated and combined. The deformation signal score may be used as a basis to keep or discard intraocular pressure measurements in a non-contact tonometer, and/or as a basis to conduct further diagnostic screening.

Abstract: A tool for calibrating a non-contact tonometer (NCT) comprises a body having a mating feature configured for removably mounting the body on the nosepiece or on the measurement head of the NCT, a pressure sensor carried by the body and arranged to receive an air pulse discharged by the NCT to provide a pressure signal in response to the air pulse, and a radiation emitter carried by the body, wherein the radiation emitter provides a pseudo-applanation event when the pressure signal reaches a predetermined level that is detectable by the NCT as though an actual corneal applanation had taken place. In one embodiment, the mating feature includes a mounting orifice for receiving a portion of the nosepiece. In another embodiment, the mating feature includes a pair of mounting pins sized for receipt by a corresponding pair of mounting holes in the measurement head of the NCT.

Abstract: An apparatus comprises a spectrophotometer system configured to measure light absorbance by a tear sample, a refractometer system configured to measure refractive index of the tear sample, and an evaluation unit programmed to calculate an osmolarity of the tear sample based on the measured absorbance and refractive index and stored calibration curves. The spectrophotometer and refractometer systems may share a common prism contacted by the tear sample during measurement. The evaluation unit may be programmed to carry out steps of a method for determining osmolarity of the tear sample in accordance with the invention. The osmolarity of the tear sample may be used as an indicator in diagnosing dry eye.

Abstract: A tool for calibrating a non-contact tonometer (NCT) comprises a body having a mating feature configured for removably mounting the body on the nosepiece or on the measurement head of the NCT, a pressure sensor carried by the body and arranged to receive an air pulse discharged by the NCT to provide a pressure signal in response to the air pulse, and a radiation emitter carried by the body, wherein the radiation emitter provides a pseudo-applanation event when the pressure signal reaches a predetermined level that is detectable by the NCT as though an actual corneal applanation had taken place. In one embodiment, the mating feature includes a mounting orifice for receiving a portion of the nosepiece. In another embodiment, the mating feature includes a pair of mounting pins sized for receipt by a corresponding pair of mounting holes in the measurement head of the NCT.

Abstract: An ophthalmic instrument that discharges a fluid pulse to deform the cornea of a test subject is improved by reducing the working distance between a nosepiece or a discharge tube from which the fluid pulse is discharged and the eye of the test subject. The invention improves measurement repeatability and patient comfort.

Abstract: A tool for calibrating a non-contact tonometer (NCT) comprises a body having a mating feature configured for removably mounting the body on the nosepiece or on the measurement head of the NCT, a pressure sensor carried by the body and arranged to receive an air pulse discharged by the NCT to provide a pressure signal in response to the air pulse, and a radiation emitter carried by the body, wherein the radiation emitter provides a pseudo-applanation event when the pressure signal reaches a predetermined level that is detectable by the NCT as though an actual corneal applanation had taken place. In one embodiment, the mating feature includes a mounting orifice for receiving a portion of the nosepiece. In another embodiment, the mating feature includes a pair of mounting pins sized for receipt by a corresponding pair of mounting holes in the measurement head of the NCT.

Abstract: An ophthalmic instrument that discharges a fluid pulse to deform the cornea of a test subject is improved by reducing the working distance between a nosepiece or a discharge tube from which the fluid pulse is discharged and the eye of the test subject. The invention improves measurement repeatability and patient comfort.

Abstract: A system for delivering a touch sensitive screen task to a subject includes a touch sensitive display for presenting visual stimuli to a subject and for providing a response of the subject, hand position monitoring unit(s) for receiving input indicative of the position of a hand of the subject and for providing output signals representing said position and a controller/processor unit operatively coupled to the touch sensitive display unit and to the hand position monitoring unit(s) for receiving output signals from the hand position monitoring unit(s) and for processing the output signals to control the displaying of the visual stimuli on the touch sensitive display unit. A method for operating the system includes receiving from the subject signals representing a response of the subject to visual stimuli, receiving signals indicative of the position of the subject's hand and processing the signals to control the presenting of visual stimuli.

Abstract: In an ophthalmic instrument that directs a fluid pulse at a cornea to cause reversible deformation of the cornea and monitors the corneal deformation to generate a deformation signal, the shape of the deformation signal is analyzed with respect to deformation signal data from a statistical population of eyes to calculate a deformation signal score indicating a degree of probability that the deformation signal corresponds in shape to a normal deformation signal for normal eyes in the population. In calculating the deformation signal score, significant geometrical signal parameters are calculated and combined. The deformation signal score may be used as a basis to keep or discard intraocular pressure measurements in a non-contact tonometer, and/or as a basis to conduct further diagnostic screening.

Abstract: An apparatus comprises a spectrophotometer system configured to measure light absorbance by a tear sample, a refractometer system configured to measure refractive index of the tear sample, and an evaluation unit programmed to calculate an osmolarity of the tear sample based on the measured absorbance and refractive index and stored calibration curves. The spectrophotometer and refractometer systems may share a common prism contacted by the tear sample during measurement. The evaluation unit may be programmed to carry out steps of a method for determining osmolarity of the tear sample in accordance with the invention. The osmolarity of the tear sample may be used as an indicator in diagnosing dry eye.

Abstract: A method and apparatus for measuring intraocular pressure of an eye use an empirically derived function wherein an inward applanation pressure P1 and an outward applanation pressure P2 obtained during a corneal deformation cycle caused by a fluid pulse are separately weighted so as to minimize cornea-related influence on the intraocular pressure value calculated by the function. In one embodiment, the function is optimized, at least in part, to minimize change in calculated IOP between measurements made before surgical alteration of the cornea and measurements made after surgical alteration of the cornea.