Bi-Curved Tonometer Tip for Accurate Cornea-Independent IOP Measurement

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Solution Overview

Problem

Existing Goldmann-type tonometers require correction for corneal thickness and stiffness, leading to inaccuracies in intraocular pressure measurements due to non-zero corneal thickness and stiffness variations.

Innovation Solution

A tonometer tip with a cornea-contacting surface featuring a central concave portion and a peripheral portion with opposite curvature, minimizing corneal deformation during applanation, eliminating the need for pachymetry and corneal thickness corrections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional Goldmann-type tonometer with a planar corneal contact surface is used, then the device structure is simple and easy to manufacture, but measurement precision deteriorates due to corneal thickness and stiffness variations requiring correction

Engineering Contradiction:

Improveintraocular pressure measurement accuracyVSAvoidcorneal contact member structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The corneal contact member features a curved front surface with a specific radius of curvature (e.g., 7.7mm) that matches the corneal curvature. This spherical/curved geometry allows the contact surface to conform to the cornea's shape, creating uniform areal contact and eliminating the need for pachymetry corrections, thereby improving measurement precision while maintaining reasonable structural complexity

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The corneal contact member has different curvature characteristics in different regions: a central corneal contact surface portion with one radius of curvature and a peripheral surface portion with a different radius of curvature. This local variation in geometric properties optimizes contact with the cornea while minimizing deformation, addressing the measurement accuracy problem without excessive structural complexity

Inventive Principle:

Principle #3Local quality

2Measurement precision

If a corneal contact member with matched curvature to the cornea is used, then measurement precision improves by eliminating pachymetry requirements, but device complexity increases due to the specialized curved surface geometry

Engineering Contradiction:

Improveintraocular pressure measurement accuracyVSAvoidcorneal contact member fabrication

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The corneal contact member is designed with a spherical or curved surface geometry that matches the corneal curvature (e.g., radius of curvature of 7.7mm). This standardized curved shape can be manufactured using conventional spherical grinding, polishing, or molding techniques, making fabrication feasible while achieving the precision benefits of curvature matching

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention specifies particular geometric parameters for the corneal contact member, such as a radius of curvature of approximately 7.7mm and specific aperture dimensions. By defining precise parameter ranges, the design balances manufacturing feasibility with the need to match corneal curvature for accurate measurements without requiring overly complex or custom fabrication processes

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the corneal contact surface has a complex curved geometry to minimize deformation, then measurement precision improves, but the area of contact may be reduced affecting measurement reliability

Engineering Contradiction:

Improvecorneal deformation minimizationVSAvoidcorneal contact area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The curved front surface of the corneal contact member with radius of curvature approximately matching the cornea (e.g., 7.7mm) creates a large areal contact region when pressed against the cornea. This spherical geometry ensures extensive contact area while the curvature matching minimizes corneal deformation, simultaneously achieving both measurement precision and reliability

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The corneal contact member features different curvature characteristics in different regions: a central corneal contact surface portion optimized for minimal deformation and a peripheral surface portion with different curvature. This local differentiation allows the central region to maintain corneal shape for precise measurement while the overall structure provides sufficient contact area for reliability

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12514447B2Tonometer tip and use of same

Publication Date: 2026.01.06 CATS TONOMETER LLC

AI summary

Ophthalmological device including an applanation tonometer tip having a bi-curved cornea-contacting surface and method of using such device for measurement of intraocular pressure. The cornea-contacting surface includes a first rotationally symmetric portion a curvature of which is substantially adapted to that of a typical cornea and a second rotationally symmetric portion that is peripheral to and adjoining the first portion. In operation, the applanation of the cornea in an area corresponding to the first portion of the cornea-contacting surface is substantially negligible.