Reichert, Inc.

Norlin Music, Inc.

Leica Gmbh

Other

Leica Microsystems Inc.

Norlin Industries, Inc.

Moog Music, Inc.

Cambridge Instruments Inc.

David A Luce

Melville Clark, Jr

Christopher J Percival

Donald E Miller

Russell J Bonaventura

James L Scott

Douglas H Hoover

Joseph L Zelvin

David G Kelkenberg

David L Beverly

Anthony Marchese

Paul J Klock

Bernard Grolman

Bruce Siskowski

Matthew Severns

Srdjan Krstanovic

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.

Determination of continuous dynamic corneal viscoelastic bending moduli

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.

Ophthalmic diagnostic instrument and method

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.

Tonometer calibration tool

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.

Subsystems and methods for non-contact corneal deformation

A method and apparatus for measuring intraocular pressure of an eye use an empirically derived function wherein an inward applanation pressure Pand an outward applanation pressure Pobtained 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.

Method and apparatus for determining true intraocular pressure

A method and apparatus for measuring corneal resistance to deformation use an empirically derived function wherein an inward applanation pressure Pand an outward applanation pressure Pobtained 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.

Method and apparatus for measuring corneal resistance

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.

Method and apparatus for tear film measurement

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.

Method and apparatus for measuring biomechanical characteristics of corneal tissue

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.

Duel mode non-contact tonometer

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.

Method for eliminating error in tonometric measurements

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.

Non-contact tonometer having improved air pump

An apparatus for calibrating a non-contact tonometer comprises an electronic eye having a damped pressure sensor for receiving a tonometer air pulse and providing a pressure signal in response to the air pulse, and an applanation simulator connected to the pressure sensor for providing a pseudo-applanation event when the pressure signal reaches a predetermined level corresponding to a known IOP measurement standard. A method for calibrating a non-contact tonometer using the inventive calibration apparatus is also described.

A hand-held non-contact tonometer comprises a housing having a handle portion for enclosing a rechargeable D.C. power source and an upper head portion for enclosing alignment and tonometric measurement systems of the tonometer. An operator can directly view the patient's eye along an optical axis extending through the head portion of the housing, and an instructional display image is superimposed with the directly viewed image of the eye to guide the operator in X-Y-Z alignment based on data supplied by an afocal position detection system. A transceiver for wireless data exchange and a recharging support stand are also provided.

Growing community of inventors

Clarence Center, NY, United States of America

David A Luce