Phase-Sensitive OCT for Anterior Segment Aberration Measurement
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Solution Overview
Problem
Current ophthalmic refractive surgical methods rely on ultrasonic biometry for measuring eye aberrations, which are less precise compared to Optical Coherence Tomography (OCT), and conventional OCT intensity imaging struggles to accurately convert topographic data into actual optical aberrations due to tissue inhomogeneity.
Innovation Solution
Phase-sensitive Optical Coherence Tomography techniques measure optical aberrations in the anterior segment of the eye by calculating the optical phase shift between the anterior surface of the cornea or lens and a reference surface, eliminating the need for a coverslip and enhancing measurement sensitivity to sub-wavelength precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional OCT intensity imaging is used to measure eye aberrations, then the measurement process is simple, but the measurement precision is insufficient due to tissue inhomogeneity preventing accurate conversion of topographic data to optical aberrations
Solution Approach 1:
The patent changes the measurement parameter from intensity imaging to phase-sensitive detection. By measuring optical phase shifts instead of intensity variations, the system achieves sub-wavelength precision (20 picometers) in measuring optical path differences caused by tissue inhomogeneity, directly resolving the limitation of conventional OCT intensity imaging
Solution Approach 2:
The patent replaces the mechanical/physical measurement approach (ultrasonic biometry and conventional OCT intensity imaging) with an optical phase measurement system. The phase-sensitive OCT apparatus uses interferometric detection to measure optical path differences, substituting mechanical measurement methods with optical field-based measurement for superior precision
2Measurement precision
If ultrasonic biometry is used for measuring eye aberrations, then the device complexity is low, but the measurement precision is insufficient compared to OCT
Solution Approach 1:
The patent replaces ultrasonic biometry (acoustic/mechanical measurement) with optical phase-sensitive OCT. The interferometric optical measurement system provides sub-wavelength precision by detecting phase shifts in coherent light as it passes through the anterior segment, achieving measurement precision unattainable by ultrasonic methods
Solution Approach 2:
The patent changes the fundamental measurement parameter from acoustic echo time (ultrasonic) to optical phase shift. This parameter change enables measurement of optical path differences with 20 picometer sensitivity, directly addressing the precision limitation of ultrasonic biometry
3Measurement precision
If a coverslip is used as reference interface in phase-sensitive OCT, then the phase sensitivity is achieved, but the device complexity increases and measurement of actual optical aberrations is hindered
Solution Approach 1:
The patent extracts and removes the coverslip from the measurement system. By eliminating the artificial reference interface (coverslip) and using the corneal or lens surface itself as the reference, the system simplifies the apparatus while maintaining phase sensitivity and enabling direct measurement of actual optical aberrations without artificial interfaces
Solution Approach 2:
The patent implements self-service by using the eye's own optical surfaces (cornea or lens) as the reference interface. The measured surface and reference surface are both natural ocular surfaces, eliminating the need for external artificial references and enabling the system to measure itself
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
This approach provides precise measurement of optical aberrations, enabling more accurate wavefront data and improved refractive correction, with sensitivity down to 20 picometers, surpassing conventional OCT intensity imaging capabilities.
Implementation Method 1
detecting an interference pattern, the interference pattern resulting from a combination of light reflected from the eye and light reflected from a reference arm of the OCT interferometer apparatus
Implementation Method 2
calculating an optical delay between a reference surface in the anterior segment of the eye and a measured surface in the eye, based on the detected interference pattern. The calculating of the optical delay comprises measuring an optical phase shift between the reference surface and the measured surface
Data Source
AI summary
Techniques for measuring optical aberrations of the eye are disclosed. An example method comprises positioning the eye in a measurement location adjacent to a measurement arm of an optical coherence tomography (OCT) interferometer apparatus, so that source light from the measurement arm passes into the anterior segment of the eye and detecting an interference pattern, the interference pattern resulting from a combination of light reflected from the eye and light reflected from a reference arm of the OCT interferometer apparatus. Based on the interference pattern, an optical delay between a reference surface in the anterior segment of the eye and a measured surface in the eye is calculated, the reference surface being the anterior surface of the cornea or the lens, wherein said calculating comprises measuring an optical phase shift between the reference surface and the measured surface, based on the detected interference pattern.