Intraocular Lens Power Calculation Using Nucleus-Centric Distances
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Solution Overview
Problem
Current methods for determining intraocular lens (IOL) power are imprecise due to reliance on estimated anterior pseudophakic distance (EAPD) calculations, which are affected by deformities in the lens cortex and variations in natural lens thickness, leading to errors in refractive outcomes.
Innovation Solution
The method involves determining preoperative estimation of postoperative IOL position using new measurements such as Ante-Nucleus Distance (AND), Retro-Nucleus Distance (RND), and natural lens Nucleus Thickness, calculated using linear regression equations to improve the accuracy of EAPD, thereby facilitating a more precise selection of IOL power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional EAPD calculation methods are used, then the process is simple, but the measurement precision of IOL position is poor
Solution Approach 1:
The patent segments the lens measurement process into distinct components: Ante-Nucleus Distance (AND) from cornea to lens nucleus, Retro-Nucleus Distance (RND) from lens nucleus to posterior lens capsule, and Nucleus Thickness (NT). This segmentation allows each parameter to be measured and calculated independently, improving overall measurement precision while maintaining a systematic approach that doesn't overly complicate the process.
Solution Approach 2:
The patent introduces new measurement dimensions by measuring distances to the lens nucleus specifically (AND and RND) rather than just using overall lens thickness. This adds dimensional precision to the measurement system, focusing on the nuclear region which is more stable and less affected by cortical deformities, thereby improving IOL position prediction accuracy.
2Reliability
If traditional ACD-based EAPD estimation is used, then the method is simple, but the reliability of refractive outcome is poor
Solution Approach 1:
The patent changes the parameters used for EAPD estimation from traditional ACD-based measurements to nucleus-centric parameters (AND, RND, NT). By focusing measurements on the lens nucleus which remains relatively stable during cataract progression, the reliability of refractive outcome predictions is improved. The new parameters are less susceptible to variations caused by cortical lens deformities.
Solution Approach 2:
The patent incorporates postoperative APD measurements as feedback to validate and refine the EAPD prediction model. By comparing predicted EAPD values with actual postoperative APD measurements, the system can assess prediction accuracy and potentially adjust parameters, thereby improving the reliability of refractive outcomes through iterative validation.
3Measurement precision
If lens cortex deformities are present, then natural lens thickness varies, but this increases error in EAPD calculation
Solution Approach 1:
The patent extracts the measurement focus from the variable lens cortex to the more stable lens nucleus. By measuring AND (cornea to nucleus) and RND (nucleus to posterior capsule) separately, the method isolates the stable nuclear region from the deformable cortical regions. This extraction of the measurement target from the problematic cortex eliminates the harmful effect of cortical deformities on EAPD calculation precision.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
The present invention discloses systems and methods for determine preoperative estimation of postoperative IOL position (or the EAPD) in accordance with one or both of the following mathematical relationships, which are derived from linear regression: EAPD=S1+S2x AND+S3x NT+S4x AL, EAPD=W1+W2x AND+W3x RND+W4x AL, where S1, S2, S3, and S4 for equation (la) and W1, W2, W3, and W4 for equation (1b) are statistically derived linear regression constant coefficients.