Retinal Autofluorescence Mapping with OCT Signal Correction
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Solution Overview
Problem
Existing retinal auto-fluorescence (AF) imaging technologies fail to accurately reflect true lipofuscin levels in the retinal pigment epithelium due to signal attenuation by varying optical properties of media in the optical path, making it difficult to compare images across individuals and over time.
Innovation Solution
An integrated imaging system combining spectral-domain optical coherence tomography (SD-OCT) and AF, using a single broadband light source, corrects for signal attenuation by utilizing depth information from OCT to normalize AF intensities, allowing for accurate assessment of lipofuscin levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing retinal AF imaging technologies are used, then AF images can be obtained, but the images do not accurately reflect true lipofuscin levels due to signal attenuation by media in the optical path
Solution Approach 1:
The patent introduces OCT as an intermediary modality to measure and correct for signal attenuation. OCT images of the retinal layers serve as a mediator to quantify the optical path properties, which are then used to normalize and correct the AF signals, enabling accurate lipofuscin measurement despite variations in media transmission
Solution Approach 2:
The patent changes the parameter space by adding a correction factor based on OCT-measured optical properties. Instead of using raw AF intensity alone, the system transforms the measurement by dividing by the attenuation factor derived from OCT, thereby converting unreliable raw AF values into corrected values that accurately reflect true lipofuscin concentration
2Ease of operation
If a single AF imaging modality is used, then imaging is simple, but comparison across individuals and time is difficult due to varying optical properties
Solution Approach 1:
The patent merges AF imaging with OCT into a single integrated system that captures both modalities simultaneously. This combination allows the system to maintain the simplicity of a single imaging procedure while adding the capability to correct for optical variations through the combined OCT data, enabling reliable cross-individual and cross-time comparisons
3Area of stationary object
If AF signals are transmitted through different retinal layers and anterior segments, then comprehensive imaging is achieved, but signal attenuation by these layers reduces measurement accuracy
Solution Approach 1:
The patent implements a feedback mechanism where OCT measurements of retinal layer optical properties are used to correct the AF signals. The OCT data provides feedback about the attenuation characteristics of each layer, allowing the system to compensate for signal loss and restore measurement accuracy while maintaining comprehensive imaging coverage
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 monitoring of lipofuscin levels, establishing standard AF levels for different age groups, correlating disease stages, and measuring treatment outcomes, replacing existing technologies for effective lipofuscin monitoring in ophthalmology clinics.
Implementation Method 1
Lipofuscin is a complex lipid/protein aggregate formed in the retinal pigment epithelium (RPE) of the eye as nondegradable end products from phagocytosis of shed photoreceptor outer segments. Lipofuscin granules are considered to be toxic to the RPE and thought to contribute to the pathogenesis of age-related macular degeneration (AMD).
Implementation Method 2
Instruments such as optical coherence tomography (OCT) [1,2] and retinal auto-fluorescence (AF) imaging [3,4] are important imaging modalities in both ophthalmic clinics and research, each capable of imaging different aspects of the retina. OCT is a low-coherence interferometry based imaging modality and primarily provides structural imaging of the retina with microscopic depth resolution.
Implementation Method 3
AF signals emitted by lipofuscin travel through different retinal layers and the anterior segments of the eye before reaching an imaging receiver. The fluorescent signals will therefore be affected and attenuated by those layers, which can have different optical properties. Existing retinal AF technologies do not take into consideration the attenuation of fluorescent signals by the media present in their optical path.
Data Source
AI summary
Imaging systems and methods of using the same are provided for monitoring the quantity of fluorescent pigment, for example lipofuscin, in the retinal pigment epithelium (RPE) layer of a retina in vivo. Various imaging modalities can be integrated into a single system and excited by a single broadband light source for the monitoring of the fluorescent pigment. The influence of varying optical properties found in the optical path of the pigment's auto-fluorescence between the RPE and an image receiver can be corrected.