Multifocal Lens Imaging for Accurate Visual Axis Identification
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Solution Overview
Problem
Conventional methods for determining the visual axis of the eye are inaccurate, leading to misalignment of multifocal and bifocal lenses during surgical implantation, which impede their effectiveness.
Innovation Solution
A method using a multifocal optical lens with spatially coinciding optical centers, combined with a fixation light beam and imaging system, to accurately locate the visual axis by aligning multiple images on the retina.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the visual axis location is approximated as halfway between the optical axis and corneal vertex, then the measurement process is simple, but the measurement precision is poor
Solution Approach 1:
The patent replaces mechanical/appearance-based approximation methods with an optical physics-based method. By using a multifocal lens to create multiple retinal images and detecting their spatial coincidence, the system objectively determines the visual axis location through optical principles rather than subjective estimation, thereby improving measurement precision without significantly increasing operational complexity
Solution Approach 2:
The patent introduces a multifocal lens as an intermediary device between the light source and the retina. This lens creates multiple virtual images at different focal planes, allowing the visual axis to be indirectly determined through the spatial relationship between these images and their coincidence point, transforming a difficult direct measurement into an easier indirect measurement process
2Device complexity
If conventional approximation methods are used, then the device complexity is low, but the reliability of lens placement is compromised
Solution Approach 1:
The patent employs a multifocal lens that serves multiple functions: it acts as both a diagnostic tool for determining visual axis location and a therapeutic element for presbyopic correction. The same optical element creates multiple retinal images for measurement while also providing the corrective refractive power needed for vision treatment, thereby improving reliability without proportionally increasing device complexity
Solution Approach 2:
The system uses image detection and spatial analysis to provide feedback about the alignment between the multifocal lens and the patient's visual axis. By monitoring the coincidence of multiple retinal images and comparing their positions, the system can accurately determine the visual axis location and provide real-time information for precise lens placement during surgical procedures
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 precise identification of the visual axis, improving the alignment of corrective lenses and ophthalmic procedures such as LASIK and PRK surgery.
Implementation Method 1
A fixation light beam is generated and directed towards the patient's eye, which forms two or more images near the patient's retina that correspond with the two or more optical powers of the multifocal lens
Implementation Method 2
capturing images of the patient's eye and the optical lens along a direction of the fixation light beam
Data Source
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AI summary
The present disclosure generally relates to methods and apparatus for accurate identification of the visual axis of the eye. In one embodiment, a visual axis identification system includes a fixation light source, a camera, a processing system, and a multifocal lens. The patient focuses their gaze through the multifocal lens and onto a fixation light beam provided by the fixation light source. The passage of the fixation light beam through the multifocal lens creates two or more images on or near to the patient's retina. The multifocal lens and/or the patient's eye are then moved relative to each other while the patient continuously maintains their gaze on the fixation light beam. The patient's visual axis may be located by determining the location of the optical center of the multifocal trial lens relative to the patient's eye when the centers of the multiple images coincide on the retina.