Multi-Wavelength Corneal Pachymetry for IOP-Separated Biomechanics
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Solution Overview
Problem
Current methods for measuring corneal biomechanical properties are limited by the need to separate intraocular pressure variations from corneal abnormalities, are time-consuming and expensive, lack precision for small spatial or temporal variations, and cannot simultaneously measure tear film thickness and corneal thickness with high accuracy, especially in vivo.
Innovation Solution
An apparatus using a multi-wavelength optical source to generate a converging array of beamlets on the cornea, combined with a two-dimensional sensor array to capture interference signals, allowing for simultaneous measurement of corneal properties and tear film dynamics with high precision and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical coherence elastography is used to measure corneal biomechanical properties, then biomechanical response can be detected, but intraocular pressure variations cannot be separated from corneal abnormalities
Solution Approach 1:
The measurement is divided into multiple independent components: tear film thickness measurement, corneal thickness measurement, and biomechanical response measurement. By segmenting the measurement process and using multiple wavelength beams targeted at different interfaces (tear film anterior surface, corneal posterior surface), the system can separately quantify IOP effects from genuine corneal abnormalities.
Solution Approach 2:
The tear film is used as an intermediary element in the measurement process. By measuring the tear film thickness and its response to pressure changes, the system can indirectly assess corneal biomechanics while using the tear film as a reference to separate IOP-induced effects from corneal pathology.
2Measurement precision
If Brillouin microscopy is used to map mechanical strength across the cornea, then longitudinal modulus can be measured, but the apparatus is expensive and time-consuming requiring high-resolution spectrometer and high on-eye optical intensity
Solution Approach 1:
The patent replaces complex mechanical scanning systems with a static multi-wavelength optical system. Instead of using a scanning mechanism to map the cornea, the system uses multiple wavelength beams that simultaneously illuminate different regions, eliminating the need for mechanical movement and high-resolution spectrometers while maintaining measurement precision.
Solution Approach 2:
The optical system is designed to perform multiple functions simultaneously: measuring tear film thickness, corneal thickness, and biomechanical properties all in one setup. The multi-wavelength beam configuration allows the same apparatus to assess multiple corneal parameters without requiring separate expensive instruments.
3Quantity of substance
If single-point pachymetry measurements are performed sequentially, then corneal thickness can be measured at different points, but motion-related artifacts are introduced and precision for small variations is insufficient
Solution Approach 1:
The system performs preliminary simultaneous measurements of corneal thickness and tear film thickness at multiple points before applying any mechanical stimulus. This baseline mapping allows the system to detect small variations and motion artifacts by comparing pre-stimulus and post-stimulus states, thereby maintaining high precision.
Solution Approach 2:
The measurement approach transitions from sequential single-point measurements to simultaneous multi-point mapping. By adding the temporal dimension of simultaneous measurement across multiple spatial points, the system can distinguish genuine corneal variations from motion artifacts that would appear as inconsistencies across the measurement field.
4Measurement precision
If optical reflectometry techniques are used to measure tear film thickness with high precision, then nanometer-level accuracy is achieved, but the technique is not well suited for measuring corneal thickness which is two orders of magnitude greater
Solution Approach 1:
The system changes the optical parameters by using multiple wavelengths simultaneously. This allows the same optical path to measure both the thin tear film (using wavelength-sensitive interference) and the thicker cornea (using the same path for differential measurement), achieving nanometer-level precision for the tear film while also capturing corneal thickness information.
Solution Approach 2:
The patent merges the measurement of tear film thickness and corneal thickness into a single integrated optical measurement process. By combining multiple wavelength beams in the same optical path, the system simultaneously captures interference patterns from both the tear film anterior surface and the corneal posterior surface, making the system versatile for measuring structures of vastly different dimensions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables snapshot, in-vivo measurement of corneal properties and tear film dynamics with nanometer-level accuracy, providing spatially resolved biomechanical responses to intraocular pressure fluctuations and external stimuli, while correcting for eye motion artifacts.
Implementation Method 1
a two-dimensional sensor array for capturing an interference signal comprising reflected or scattered light from said first surface or interface and reflected or scattered light from a second surface or interface of said cornea
Implementation Method 2
said interference signal containing information on relative phase between the first and second surfaces or interfaces across the portion of said cornea illuminated by said beamlets
Data Source
Figure 1A
Figure 1B~1D
Figure 2~3
AI summary
Apparatus and methods are presented for non-contact in-vivo measurement of one or more properties of a cornea or tear film with spatial resolution. In certain embodiments the cornea/tear film is probed at substantially normal incidence with a converging array of beamlets from a multi -wavelength optical source, and the reflected light analysed interferometrically to generate a time sequence of pachymetry maps. Thickness variations arising from differences between the external and intraocular pressure, e.g. from the ocular pulse or externally applied pressure changes, are measured and analysed to obtain information on a biomechanical response of the cornea. In preferred embodiments the time variation in tear film thickness is measured and subtracted to yield normalised pachymetry data for the biomechanical analysis. In certain embodiments the apparatus is configured to measure the dynamics and profile of the tear film, using either converging or substantially parallel arrays of beamlets.