Abstract: A method and apparatus for measuring corneal resistance to deformation 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 dependence of the calculated corneal resistance factor (CRF) on intraocular pressure. In one embodiment, the function is optimized, at least in part, to maximize statistical correlation between the calculated corneal resistance factor (CRF) and central corneal thickness.

Abstract: Tear film is measured without contacting the eye by comparing reflectance from the eye when the tear film is undisturbed with reflectance from the eye when the when the tear film is disturbed. If the reflectance levels differ somewhat, it is an indication that a healthy tear film exhibiting good specular reflection was present initially and was disturbed by the air pulse. However, if the reflectance levels are close to one another, it is an indication that a less-than-normal tear film was present initially (dry eye). In a described embodiment, tear film is disturbed by an air pulse directed at the eye, and a photosensitive detector is positioned to receive light from an illumination beam after the beam is reflected by the eye to generate a reflectance signal. The reflectance signal is evaluated to calculate a tear film index.

Abstract: A syringe pump and associated computer are provided to achieve an ultra-low flow rate. The computer may generate syntax commands to a motion controller of the syringe pump to displace a plunger by a selected number of steps or increments and pause a period of time before repeating the displace and pause steps. The cycle may be repeated until a desired end condition has been reached. The syringe pump and computer may be embodied as separate linked units or as a standalone unit wherein the computer is an embedded controller located within the syringe pump housing. The invention may also be embodied as a method for achieving ultra-low flow.

Abstract: A method of providing an eye diagnosis. The method includes displaying stimuli to a patient, receiving indications of locations in which the stimuli were perceived by the patient, analyzing the spatial relationship between at least some of the received indicated locations and classifying the patient with regard to a retinal related disease, at least partially based on the spatial analysis.

Abstract: An analytical instrument for making measurements based on detection of an SPR resonance minimum or a refractometer transition shadowline on a detector array is improved by configuring a diaphragm of the instruments illumination system to include a first aperture, a second aperture, and an opaque region between the first and second apertures, wherein the opaque region of the diaphragm casts a shadow on the detector array to provide a reference minimum from which a relative location of the resonance minimum or transition shadowline is measurable. By establishing a reference minimum on the detector array as a reference location for relative measurement, the instrument compensates for signal drift and other instrument variations. The diaphragm may include additional apertures and opaque regions for generating additional reference minima over the extent of the detector array.

Abstract: A multiple focal length transducer comprising a first end allowing cooperable attachment to an ultrasound bio-microscope. A second end allowing contact with a water bath. An adjustable connecting portion allowing multiple focal lengths. The adjustable connecting portion may be allowed to flex similar to an accordion. The multiple focal length transducer is preferably produced to be sterile from medical grade silicone and is disposable.

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.

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.

Abstract: The invention provides a hypoallergenic disposable cover for the probe tip of a contact tonometer comprising a thin film having an ultimate elongation in the range of 500 to 1000%, a tensile strength in the range of 1000 to 5500 psi and a modulus of elasticity at 100% strain in the range of 50 to 2000 psi, whereby when installed onto the probe tip, the cover creates a barrier against microorganisms from the eye of a patient to said probe tip during a tonometric examination while allowing measurement of intraocular pressure through the disposable tip cover.

Abstract: A method for measuring a biomechanical characteristic of corneal tissue of a cornea comprises the steps of measuring a geometric parameter of the cornea, measuring hysteresis associated with deformation of the cornea, and evaluating the measured geometric parameter and hysteresis. In an ophthalmic system for practicing the method, a pachometer is used to measure corneal thickness and a tonometer is used to measure hysteresis, and the measurement data is supplied to a computer for evaluation. A related method for prequalifying LASIK patients comprises the steps of establishing a multi-dimensional space wherein a first dimension is a geometric corneal parameter and a second dimension is hysteresis associated with corneal deformation, measuring the geometric corneal parameter and hysteresis of the patient's cornea, registering the geometric corneal parameter and corneal hysteresis in a data point in the multi-dimensional space, and evaluating a location of the data point in the multi-dimensional space.

Abstract: An alignment system for an ophthalmic instrument comprises an optical axis along which an operator can directly view the patient's eye and the patient can fixate on a dark fixation target surrounded by a bright background that helps to illuminate the eye for operator viewing. A position detection system utilizing stored geometrical relationships determined by multiple regression during instrument calibration computes X-Y-Z alignment status of the instrument relative to a patient's eye based on local x-y position information from a pair of lateral detectors receiving corneally reflected light from a corresponding pair of lateral light sources. A heads-up display image is provided along an optical axis of the instrument for supplying instructive cues to an operator for moving the instrument to achieve alignment based on signal information from the position detection system, whereby the operator sees both a direct macro-image of the patient's eye and the display image.

Abstract: A dual mode non-contact tonometer allows selection between a standard measurement mode for patient comfort and an alternate measurement mode wherein pressure-time characteristics of the fluid pulse are varied to allow additional observation of corneal hysteresis associated with the dynamic measurement process. In the alternate measurement mode, measured intraocular pressure corresponding to inward applanation of the cornea and corneal hysteresis derived from a pressure differential associated with inward and outward applanation events in the same measurement pulse allows comparison with a predetermined population normality function to avoid corneal effects so that the actual status of intraocular pressure can be ascertained.

Abstract: A novel tonometry method wherein measured intraocular pressure corresponding to inward applanation of the cornea and corneal hysteresis derived from a pressure differential associated with inward and outward applanation events in the same measurement pulse allows comparison with a predetermined population normality function to avoid corneal effects so that the actual status of intraocular pressure can be ascertained. A dual mode non-contact tonometer allows selection between a standard measurement mode for patient comfort and an alternate measurement mode wherein pressure-time characteristics of the fluid pulse are varied to allow additional observation of corneal hysteresis associated with the dynamic measurement process for carrying out the novel tonometry method. Corresponding tonometry method embodiments include a method adapted for a contact tonometer and a method based on a pair of non-contact tonometer measurements taken using different air pulse pressure ramp rates.

Abstract: A hand-held automatic refractometer comprises a linear scanned array having a plurality of photoelectric cells and an optical system for directing light onto the array, the particular photoelectric cells of the array which are illuminated by said light being determined by the index of refraction of a sample substance placed on a sample surface of a prism of the optical system. A reflective surface is arranged close to the array at an acute angle thereto for directing primary light from the sample-prism boundary to the array, and for redirecting stray reflected light from the array back onto the array. The disclosed refractometer has a compact design wherein the linear array extends in a direction substantially parallel to the prism sample surface. The prism is mounted in a housing and the sample surface faces upward to allow access through a sample well of the housing, while the array is mounted in the housing facing in a downward direction.

Abstract: An apparatus for performing optical measurements comprising a light source operatively arranged to emit light along a beam path, a prism, a sensor chip mounted to a sample surface of the prism, and a detector operatively arranged to measure intensity of light reflected from the intermittent members of the metallic film. The sensor chip has a metallic film with a plurality of intermittent members, a first sample reservoir, and a second sample reservoir. The first and second reservoirs are operatively arranged to hold and position a sample on at least one member of a plurality of intermittent members of the metallic film.

Abstract: A fast position detection system and related method for an ophthalmic instrument utilize stored geometrical relationships determined by multiple regression during instrument calibration to compute X-Y-Z alignment status of the instrument relative to a patient's eye based on local x-y position information from a pair of lateral detectors receiving corneally reflected light from a corresponding pair of lateral light sources. In a preferred embodiment, the lateral detectors are quad-cell detectors. A heads-up display image is preferably provided along an optical axis of the instrument for supplying instructive cues to an operator for moving the instrument to achieve alignment, whereby the operator sees both a macro-image of the patient's eye and the display image. The speed of the position detection system makes it particularly suitable for use in hand-held ophthalmic instruments.

Abstract: An optical configuration for measuring a difference in refractive index between a first sample and a second sample comprises partitioned first and second optical interfaces symmetrically illuminated by an illumination beam to provide first and second partial beams defined by the refractive index of the first and second samples, respectively. A linear scanned array is aligned in a meridional plane of the optical configuration for detection purposes, and an optical multiplexor is provided upstream of the linear scanned array for receiving the first and second partial beams and defining first and second optical channels carrying optical signal information corresponding to the first and second partial beams. The optical multiplexor switches between optical channels, such that the linear scanned array detects either the first or second optical channel at a given time. Thus, differential measurements are possible using a single linear array.

Abstract: A non-contact tonometer of a type having a cylinder, a piston received by the cylinder for axially directed movement relative to the cylinder, and a driven member for causing the piston to move relative to the cylinder in a compression stroke to generate a fluid pulse for transfiguring a cornea is improved by decoupling the piston from the driven member to eliminate the need for critical alignment between the driven member and piston and allow the piston to be self-aligning with respect to the cylinder.

Abstract: An optical configuration for differential refractive index measurements of a test sample relative to a reference sample comprises an optical path along which an illumination beam travels to simultaneously illuminate a pair of optical interfaces on opposite sides of a meridional plane corresponding to the test sample and reference sample, respectively. Partial beams leaving the optical interfaces are optically diverged to illuminate different segments of a linear scanned array aligned in the meridional plane. The difference in location of a pair of shadowlines or a pair of resonance minimums formed by the partial beams on the array provides an indication of the refractive index difference.