Fixation Target System with Stokes Cell for Astigmatism Compensation
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Solution Overview
Problem
Conventional autorefractors and aberrometers are not completely reliable in fully relaxing the accommodation of a significant percentage of patients' eyes during refraction measurements, leading to erroneous or inaccurate results, which lacks confidence in prescriptions based solely on these measurements.
Innovation Solution
A fixation target system comprising a wavefront aberrometer with a movable stage, a Stokes cell, and a video display, where the fixation target is presented to the eye to cause accommodation, with the Stokes cell compensating for astigmatism and the processor adjusting the target size to ensure consistent visual cues, promoting full relaxation of accommodation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fixation target is used to draw the focus of the eye to its most distant refractive state, then the eye attempts to relax accommodation, but about ten percent of people do not fully relax accommodation, leading to inaccurate refraction measurements
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the size of the fixation target on the video display while moving the second movable stage. The processor electronically changes the target size parameter to create appropriate visual cues that promote full relaxation of accommodation, transforming a static fixation target into a dynamic one that adapts to elicit the desired physiological response.
Solution Approach 2:
The system incorporates feedback by using the video display to show the fixation target whose size changes in response to the movement of the second movable stage. This feedback mechanism creates a visual cue that helps patients understand the fogging process and promotes full accommodation relaxation, thereby improving the reliability of the measurement.
2Measurement precision
If the fixation target is moved away from the eye to fog the eye and stimulate relaxation of accommodation, then refraction measurement accuracy improves, but the visual cues may not be sufficient for all patients to achieve full relaxation
Solution Approach 1:
The patent changes the parameter of target size dynamically during the fogging process. By electronically adjusting the size of the fixation target on the display while moving it away from the eye, the system creates varying visual cues that enhance the fogging effect and make the accommodation relaxation process more intuitive for patients.
Solution Approach 2:
The system transitions from a static fixation target to a dynamic one that changes size during movement. The processor controls the target size parameter in real-time based on the position of the second movable stage, creating a dynamic visual experience that improves patient understanding and facilitates full accommodation relaxation.
3Device complexity
If a simple fixation target is used, then the device complexity is low, but it cannot provide sufficient visual cues for all patients to achieve full accommodation relaxation
Solution Approach 1:
The video display serves multiple functions: it presents the fixation target, provides visual feedback on target size changes, and creates dynamic visual cues during the fogging process. This multi-functionality allows a single component to deliver comprehensive visual information that promotes accommodation relaxation in diverse patient populations.
Solution Approach 2:
The system introduces dynamic parameter changes to the fixation target presentation by electronically adjusting target size during movement. This adds a layer of complexity that enhances the visual cues provided to patients, improving reliability without requiring multiple separate devices or complex mechanical structures.
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
The system effectively increases the percentage of patients achieving fully relaxed accommodation during refraction measurements, enhancing the accuracy and reliability of refractive state measurements, thereby improving the confidence in prescriptions.
Implementation Method 1
a Stokes cell disposed on the first stage in the optical path between the second lens and the third lens
Implementation Method 2
an optical system disposed in an optical path between the fixation target and the eye, wherein the optical system includes: a first lens which is not disposed on the first stage or second stage, a second lens and a third lens, each disposed on the first stage and not disposed on the second stage, a fourth lens disposed on the second stage
Data Source
AI summary
A system includes: a first movable stage which is movable with respect to an eye of a subject; a second movable stage mounted on the first movable stage, wherein the second movable stage is movable with respect to the first movable stage; a fixation target disposed on the second movable stage; and an optical system disposed in an optical path between the fixation target and the eye, wherein the optical system is configured for projecting the fixation target upon the eye to accommodate the eye. The optical system includes a Stokes cell in the optical path between the fixation target and the eye. The optical system non-telecentrically projects the fixation target upon the eye.