Ophthalmic Topography Mapping with Two-Photon Deep-Tissue Focusing
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Solution Overview
Problem
Traditional optical techniques for high-resolution imaging in biological materials are limited to near-surface measurements (less than 100 µm) due to light scattering and blurring, and one-photon absorption processes are inadequate for deeper imaging.
Innovation Solution
A medical system utilizing a laser beam with multiple frequencies and a two-photon absorption (TPA) detector to determine multiple focal point distances and intensity values, adjusting mirrors and beam expanders to focus the laser beam, and determining a topography based on these measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical techniques utilizing one-photon absorption are used, then high-resolution imaging can be achieved near the surface (less than 100 µm), but imaging depth is limited due to light scattering and blurring
Solution Approach 1:
The patent changes the fundamental parameter of light absorption from one-photon to two-photon absorption. This parameter change enables the system to achieve both high-resolution imaging and increased imaging depth. The two-photon absorption process has a quadratic dependence on light intensity, which provides inherent optical sectioning and reduces scattering effects, allowing deep imaging while maintaining resolution.
Solution Approach 2:
The patent employs a composite approach by combining multiple frequency laser beams (e.g., fundamental frequency and second harmonic) to achieve two-photon absorption. This composite light field enables simultaneous excitation of different fluorophores at different depths, resolving the contradiction between surface resolution and deep tissue imaging capability.
2Measurement precision
If white light interferometry is used to measure surface height variations, then three-dimensional surface mapping can be obtained, but the technique is limited to near-surface measurements
Solution Approach 1:
The patent replaces traditional mechanical/optical interferometry with a two-photon absorption-based measurement system. This substitution enables depth-resolved topography measurement by utilizing the depth-dependent intensity profile of focused laser beams, allowing measurement of subsurface features while maintaining surface resolution.
Solution Approach 2:
The patent adds the depth dimension to surface topography measurement by utilizing optical sectioning through two-photon absorption. The system can measure height variations at different depths simultaneously, transforming a two-dimensional surface mapping technique into a three-dimensional volumetric measurement capability.
3Length of stationary object
If light is focused deeper into biological material, then imaging depth increases, but light scattering and blurring worsen
Solution Approach 1:
The patent changes the absorption mechanism from linear (one-photon) to quadratic (two-photon) dependence on light intensity. This parameter change creates a sharper focal volume with reduced scattering effects, as the two-photon absorption probability is proportional to the square of the local intensity, naturally confining the excitation to the focal plane even at greater depths.
Solution Approach 2:
The patent utilizes pulsed laser excitation with specific pulse durations to achieve two-photon absorption. The periodic pulsing allows for optimal photon density accumulation at the focal point while minimizing total energy deposition, thereby maintaining imaging clarity at increased depths through controlled excitation timing.
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 accurate determination of surface topography and incision depth in biological tissues, maintaining precise cutting depths and contours without deviations, facilitating advanced ophthalmic procedures.
Implementation Method 1
receive, via a two-photon absorption (TPA) detector, at least a portion of the laser beam reflected from a surface of a patient interface
Implementation Method 2
receive, via a two-photon absorption (TPA) detector, at least a portion of the laser beam reflected from a surface of a patient interface
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
The disclosure provides a system that may: produce the laser beam; determine multiple focal point distances associated with respective multiple positions of a plane orthogonal to the laser beam via for each position of the multiple positions: adjust at least one mirror to target the laser beam to the position; determine multiple intensity values associated with respective multiple interim focal point distances; determine a maximum intensity value of the multiple intensity values; determine an interim focal point distance of the multiple interim focal point distances respectively associated with the maximum intensity value; and determine a focal point distance of the multiple focal point distances as the interim focal point distance of the multiple interim focal point distances respectively associated with the maximum intensity value; and determine a topography of a surface of a patient interface based at least on the multiple focal point distances associated with the respective multiple positions.