Purkinje Reflection Tracking for Real-Time IOL Position and Tilt
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Solution Overview
Problem
Existing eye-tracking technologies lack the combination of accuracy, dynamic range, and speed required for precise real-time measurement of intraocular lens (IOL) position and tilt during surgical procedures, particularly due to challenges with low-scatter optical materials and complex data processing in Optical Coherence Tomography (OCT) systems, and difficulties in accurately tracking Purkinje reflections.
Innovation Solution
An eye-tracking optical instrument and methodology that synchronizes infrared LED illumination with a CCD iris imaging camera to dynamically track Purkinje reflection spots, combined with Optical Coherence Tomography (OCT) for real-time XYZ position and tip/tilt measurement of ocular structures, using programmable LED light sources to identify unique patterns of reflections from the cornea and internal ocular surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Optical Coherence Tomography (OCT) is used to measure internal structures, then measurement capability is provided, but system complexity and data processing requirements increase
Solution Approach 1:
The system separates measurement functions into distinct modules: Purkinje spot tracking for XY position and tip/tilt, and OCT for Z-position. Each module processes specific aspects of IOL positioning independently, reducing overall system complexity while maintaining comprehensive measurement capability.
Solution Approach 2:
The optical system is designed to perform multiple functions through a shared optical path: Purkinje spot detection for lateral positioning, OCT for axial positioning, and potential wavefront sensing. This multi-functional approach reduces the need for separate systems while maintaining measurement precision.
2Speed
If Purkinje reflection tracking is used to monitor eye movement, then real-time tracking capability is achieved, but accuracy is reduced due to low-scatter optical materials
Solution Approach 1:
The system uses infrared illumination specifically targeted at the corneal surface where Purkinje reflections occur, enhancing the local signal quality. The infrared wavelength is chosen to optimize reflection contrast from the cornea while minimizing scattering from internal ocular structures.
Solution Approach 2:
The illumination system combines infrared LEDs with specific optical filters and coatings designed to enhance Purkinje reflection contrast. The composite optical path includes components optimized for infrared wavelengths to maximize signal quality from low-scatter materials.
3Speed
If synchronized LED illumination and CCD camera are used to track Purkinje spots, then tracking speed is improved, but system synchronization complexity increases
Solution Approach 1:
The LED illumination and CCD camera are integrated into a single synchronized imaging system with shared timing control. The synchronization is achieved through a unified control architecture that triggers both illumination and image capture simultaneously, reducing the need for separate synchronization mechanisms.
Solution Approach 2:
The system uses periodic pulsed illumination synchronized with the camera frame rate to capture Purkinje spots at regular intervals. This periodic action ensures consistent timing while simplifying the control logic compared to continuous operation.
4Measurement precision
If multiple light sources are used to create unique reflection patterns, then identification accuracy is improved, but device complexity increases
Solution Approach 1:
The light source array is divided into multiple independently controllable groups or individual LEDs, each contributing to specific features of the reflection pattern. This segmentation allows the system to create complex unique patterns while maintaining simple control of individual elements.
Solution Approach 2:
The system creates optical copies of the light source pattern through Purkinje reflections on the corneal surface. Each light source generates a corresponding reflection spot, and the arrangement of these spots creates a unique pattern that copies the spatial configuration of the light sources, enabling identification without direct observation of the light sources themselves.
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 high-precision, real-time tracking of IOL position and tilt, overcoming limitations of existing systems by providing accurate XYZ positioning and tip/tilt measurements, even with low-scatter materials, and enhancing surgical precision.
Implementation Method 1
an array of infrared LED light sources
Implementation Method 2
track the motion of Purkinje reflection spots generated by the array of infrared LED light sources on the cornea and/or internal structures of the eye
Implementation Method 3
synchronizes infrared LED illumination with a CCD iris imaging camera to dynamically track Purkinje reflection spots
Implementation Method 4
Optical Coherence Tomography (OCT) for real-time XYZ position and tip/tilt measurement
Data Source
AI summary
This disclosure teaches an eye-tracking optical instrument and methodology for dynamically tracking Purkinje reflection spots on a patient's eye in real-time, which allows the XYZ position and tip/tilt of ocular structures on or inside of the eye to be measured in real-time with high precision. When used in combination with programmable groups of infrared LED light sources, unique patterns of Purkinje reflections from the cornea and/or internal ocular surfaces within the eye may be accurately identified. An Optical Coherence Tomography (OCT) optical system and/or an off-axis Range Finding Camera may be combined with the eye-tracking optical system to provide Z-axis distance information.