D36 No. 42. ASME IMECE ? A Zonular Curvi-Linear Coordinate System for A Human Eye
James O'Flanagan, MS, FRSA
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??Advancing Ocular Biomechanics with Precision: The Zonular Coordinate System
By: James O'Flanagan, MS, FRSA
Author's Note:
Happy Halloween everybody!
This article serves as a continuation of Deck 36, No. 41: ASME IMECE ? Using Generative AI to Set Up & Run Virtual Experiments, which explored AI-driven innovations in DOE (Design of Experiments) and FEA (Finite Element Analysis). This paper was also accepted by ASME IMECE, for which we are sincerely grateful.??
Here, we focus on a novel biomechanical model, the Zonular Coordinate System (ZCS), developed specifically for simulating the human eye. We propose the integration of Generative AI and FEA as complementary tools to refine and optimize the ZCS for future research. Drawing on my experience in tire analysis, FEA, and ocular geometry from my time at an ophthalmic startup, we will also compare the ZCS to similar systems in other engineering fields.
Article Summary:
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Music by: The Marshall Tucker Band, "Can't You See." (1973).
Link Reference: https://vimeo.com/1021532787
Introduction: The Problem with Traditional Ocular Models
Traditional models used in ocular biomechanics often rely on Cartesian or spherical coordinate systems to simulate the behavior of the human eye. While these systems are mathematically convenient, they significantly oversimplify the geometry of the eye, particularly when it comes to complex, non-linear structures like the zonular fibers. This leads to several key issues:
1. Failure to Capture Non-Linear Geometries
The human eye, particularly its zonular system, exhibits a complex, curved geometry that cannot be accurately represented by Cartesian or spherical coordinates. The zonular fibers, which support the lens and regulate its movement, follow a naturally curved, non-linear path. Traditional models that assume straight-line coordinates or uniform spherical geometry fail to account for these intricacies. As a result:
Link Reference: https://www.merckmanuals.com/professional/multimedia/3dmodel/eye-anterior-and-posterior-chambers
2. Intraocular Pressure (IOP) Miscalculations
One of the most significant factors in ocular health is the regulation of intraocular pressure (IOP), which affects the shape and function of the eye’s lens. Traditional models based on spherical assumptions oversimplify the behavior of IOP, leading to flawed simulations. Inaccurate modeling of IOP has direct consequences for:
3. Challenges in Surgical Planning
Modern ocular surgeries, such as cataract removal, lens implants, and refractive surgeries, require extremely precise simulations to predict how the eye will respond to interventions. Traditional models, however, are limited by their inability to account for the non-symmetric, non-linear nature of the eye. This leads to:
4. Limited Application of Newtonian Mechanics
Newtonian mechanics, which describes how forces result in motion and deformation, relies heavily on an accurate understanding of an object's geometry. In traditional ocular models, the simplified geometry makes it difficult to apply Newton’s laws effectively. Without an accurate coordinate system:
Link Reference: https://www.britannica.com/science/Newtons-laws-of-motion
5. Inadequate Representation of Zonular Fibers
The zonular fibers, which play a key role in maintaining the shape of the lens and controlling its movement during accommodation, are highly complex in structure. They connect the ciliary body to the lens and must be modeled accurately to simulate the forces that maintain focus and eye movement. Traditional models struggle with:
Link Reference: https://www.aao.org/eye-health/anatomy/zonules#:~:text=The%20zonules%20are%20the%20tiny,the%20lens%20for%20near%20vision.
Origin and Development
While traditional models of the human eye have provided valuable insights, they often relied on simplified geometric assumptions that couldn't fully capture the complexity of the eye's structures. The Zonular Coordinate System (ZCS) addresses this by introducing a curvilinear framework that better represents the eye’s intricate geometry, particularly the zonular fibers.
The ZCS draws inspiration from both tire analysis techniques developed at Goodyear and Finite Element Analysis (FEA) element shape functions. These methodologies provide a foundation for accurately modeling non-linear geometries and biomechanical forces. In tire analysis, three key directions are utilized:
By integrating these concepts with FEA techniques, the ZCS offers a more refined tool for simulating the complex mechanics of the human eye.
Please see this link for more information about the development of a curvi-linear coordinate system for a tire similar to the ZCS proposed in this article:
Link Reference: https://www.jstor.org/stable/2312537
My Experience with Tire Geometry, FEA, and Ocular Modeling
During my time in the ophthalmic industry, I drew on my experience in tire analysis and FEA to better understand the complex geometries involved in ocular biomechanics. The Zonular Coordinate System (ZCS) emerged from these cross-disciplinary insights, where I recognized similarities between modeling tire plylines and the curvilinear nature of the eye’s zonular fibers. Both systems require a specialized coordinate system to handle non-linear geometries and accurately simulate forces along curved paths.
There was another Deck 36 Newsletter article talking about our ASME IMECE activities this year. You can read that article here:
The Zonular Coordinate System (ZCS): A Novel Solution
To address these limitations, we developed the Zonular Coordinate System (ZCS), a curvilinear coordinate system designed to mirror the natural curvature of the eye’s zonular fibers. By aligning the coordinate system with the eye’s unique geometry, the ZCS provides more accurate simulations of intraocular forces, lens movement, and zonular fiber behavior. This is critical for applications in surgical planning, especially for procedures like cataract surgeries and glaucoma management.
Euclidean Geometry Underlying the Zonular Coordinate System (ZCS)
At the core of the Zonular Coordinate System (ZCS) lies a foundation of Euclidean (or Cartesian) geometry, which serves as the baseline from which the system transitions into a curvilinear model. In its simplest form, Euclidean geometry provides the linear, flat-coordinate framework that helps define initial axes and vectors for measuring forces and movements. The ZCS then applies transformations to map these linear axes onto the curved paths of the zonular fibers. This transformation is crucial for representing the natural, non-linear structure of the eye while preserving the simplicity and computational efficiency of Euclidean geometry. By beginning with this familiar framework and adapting it to the complex curvature of the eye, the ZCS ensures accurate and efficient modeling of biomechanical forces within a dynamic, curved environment.
Plyline: An Example of A Non-Straight Variable Axis
The plyline, commonly used in tire geometry and mechanical systems, represents a non-straight, variable axis that curves in accordance with the structural properties of the material. In tire modeling, the plyline allows engineers to accurately simulate the curved paths of fibers or materials as they wrap around the tire’s structure, adapting to changes in geometry, pressure, and stress. This flexible axis is key to understanding how forces are distributed across non-linear paths, where straight-line assumptions would fail to capture the true behavior of the system. The adaptability of the plyline to follow the natural curves of materials makes it ideal for use in complex geometrical environments where precision is essential.
Link Reference: https://en.wikipedia.org/wiki/Curvilinear_coordinates
This concept translates directly into ocular biomechanics, where the human eye’s zonular fibers follow similarly complex, curvilinear paths. Traditional coordinate systems based on straight axes or uniform shapes, such as Cartesian grids, cannot represent these curves accurately. By applying the plyline methodology, we can model the eye’s structural complexities more precisely, mirroring the natural curvature of the zonular fibers and allowing for better simulation of forces and movements. This enhanced model is crucial for applications like surgical planning, where precise understanding of these dynamics leads to improved outcomes. The introduction of a non-straight variable axis, like the plyline, marks a significant step forward in accurately capturing the non-linear behaviors found in both mechanical systems and human anatomy.
Link Reference: https://www.youtube.com/watch?v=2V__naEkXVY
Comparison with Plyline-Based Tire Geometry and FEA Coordinate System Transformations
The development of the Zonular Coordinate System (ZCS) draws parallels to techniques used in engineering fields like tire analysis and Finite Element Analysis (FEA). These methods share a common goal: to accurately represent complex, curved geometries and apply forces in a meaningful way. Below, we highlight the key comparisons between ZCS, plyline-based geometry in tire analysis, and coordinate system transformations in FEA.
1. ZCS vs. Plyline-Based Tire Geometry
The ZCS is fundamentally similar to the plyline-based coordinate system used in tire analysis. In tire mechanics, a plyline follows the curved structure of the tire, allowing for more accurate modeling of stress and strain along a non-linear path. This is necessary because tires, much like the human eye, feature complex geometries that cannot be represented by traditional Cartesian coordinates.
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2. ZCS and FEA Coordinate System Transformations
Another important comparison is the use of coordinate system transformations in Finite Element Analysis (FEA). In FEA, transformations are used to convert complex, irregular geometries into a more standardized, solvable form. This process is crucial for reducing computational complexity while maintaining the accuracy of the simulation.
3. Application in Simulation and Real-World Systems
The lessons learned from tire geometry and FEA transformation systems provide valuable insights into the design and refinement of the ZCS:
The Role of Generative AI and FEA in Advancing ZCS
As we look to refine and optimize the ZCS, both Generative AI and Finite Element Analysis (FEA) play crucial roles. Each tool brings unique strengths to the research process, but they are most effective when used together.
Generative AI for Rapid Exploration
Generative AI excels at running virtual experiments across a wide range of potential ZCS configurations. By automating the generation of models and exploring a variety of physiological conditions, AI can rapidly iterate on ZCS designs, providing insights into how different parameters (e.g., fiber tension, intraocular pressure) impact the system’s performance.
FEA for Detailed Analysis and Validation
While AI is useful for broad exploration, Finite Element Analysis (FEA) provides the detailed, physics-based validation needed to ensure the accuracy of the ZCS. FEA simulates the actual mechanical behavior of the eye under various conditions, offering precise calculations of stresses, strains, and forces within the zonular fibers and lens.
Why We Need Both
The combination of Generative AI and FEA provides a balanced approach: AI explores the design space rapidly, while FEA validates the most promising configurations in detail. Together, they enable us to optimize the ZCS more efficiently and accurately.
Methodology: Integrating AI & FEA for ZCS Refinement
To optimize the Zonular Coordinate System (ZCS) for accurate ocular biomechanics modeling, a dual approach combining Generative AI and Finite Element Analysis (FEA) is used. This methodology leverages the strengths of both tools: AI rapidly explores and simulates various ZCS configurations, while FEA provides detailed, physics-based validation. Together, these techniques create an efficient and accurate system for modeling the eye’s complex structures, particularly its zonular fibers.
The following steps outline how AI and FEA are integrated to refine the ZCS, ensuring the system is robust for clinical applications such as surgical planning and glaucoma treatment.
1. Initial Exploration with Generative AI
We will first use Generative AI to run virtual experiments, simulating a variety of ZCS configurations under different physiological conditions (e.g., elevated intraocular pressure, lens dynamics). AI will adjust key parameters (e.g., fiber tension, curvature) to identify optimal configurations for further testing.
2. Detailed Simulation and Validation with FEA
Once the most promising configurations are identified by AI, we will use FEA to perform detailed simulations, calculating the precise stresses and strains within the eye. This step ensures that the ZCS conforms to real-world physics and provides the accuracy needed for clinical applications.
3. The Scientific Method: Applying AI and FEA
The development of the Zonular Coordinate System follows a structured approach based on the scientific method:
Conclusion: Advancing ZCS with Generative AI and FEA
The Zonular Coordinate System (ZCS) offers a significant advancement in the simulation of ocular biomechanics, addressing the limitations of traditional models. By integrating Generative AI for rapid exploration and FEA for detailed validation, we can refine and optimize the ZCS for clinical applications such as lens implants, glaucoma treatment, and surgical planning. This dual approach enables deeper insights into the complex interactions within the eye, leading to better research outcomes and improved medical practice.
References
In order to further ground the Zonular Coordinate System (ZCS) within the context of existing research, the following references provide essential background on both the historical development of ocular biomechanics and the innovations that differentiate the ZCS. The ZCS builds upon foundational work in Finite Element Analysis (FEA), curvilinear coordinate systems, and biomechanical modeling, but offers unique advancements through its integration of Generative AI, non-symmetric geometry modeling, and real-world clinical applications. This section will clarify how these references relate to or differ from the ZCS framework.
Explores curvilinear systems for modeling zonular fibers, focusing on static simulations of biomechanics. While related, Xu et al.’s work does not integrate AI and remains focused on static modeling. The ZCS adds a dynamic, AI-driven component for real-time modeling of complex biomechanical forces.
Provides an overview of FEA in ocular biomechanics, addressing challenges with modeling complex ocular geometries. Unlike this more traditional FEA model, the ZCS incorporates AI to refine and optimize biomechanical modeling, particularly for non-linear and non-symmetric structures like zonular fibers.
Focuses on computational modeling for cataract surgery, using traditional FEA methods for surgical planning. While Sridhar and Vasavada’s models are valuable, the ZCS’s integration of AI and non-symmetric modeling provides a more comprehensive approach for surgical planning and other clinical applications.
Early foundational work on the biomechanics of the eye, focusing on lens accommodation. The ZCS builds on Gullstrand’s foundational concepts by incorporating advanced interdisciplinary methods from tire geometry and FEA shape functions to better model the complex, dynamic behaviors of the eye.
Errata
? Zonular Fibers Complexity – Zonular fibers, which support the eye's lens, follow an intricate, non-linear path, making them particularly challenging to model with traditional coordinate systems like Cartesian grids.
? Tire Analysis Inspiration – The Zonular Coordinate System (ZCS) is inspired by curvilinear analysis used in tire mechanics, where plylines help simulate forces on curved surfaces, much like zonular fibers in the eye.
? Generative AI for ZCS – Generative AI is key in rapidly simulating various ZCS configurations, allowing researchers to test numerous hypotheses about the eye’s biomechanics before applying FEA for detailed validation.
? FEA’s Role in Medical Applications – Finite Element Analysis (FEA) has played a critical role in advancing surgical planning, especially for cataract surgeries and glaucoma treatments, by providing precise force and pressure simulations based on the ZCS model.
Abstract Submitted to ASME
The ASME IMECE is a leading global conference in mechanical engineering, where experts present cutting-edge research. Submissions undergo a rigorous peer-review process, ensuring high-quality work. Our submission for IMECE 2024 focuses on advancements in the Zonular Coordinate System (ZCS), integrating Generative AI and FEA to improve biomechanical simulations of the human eye, with potential applications in surgical planning and glaucoma treatment. Results will be presented at IMECE 2024.
Advancing Ocular Biomechanics with a Curvilinear Zonular Coordinate System & Non-Symmetric Geometry
Introduction
The biomechanics of the human eye present unique challenges due to its complex, non-spherical geometry, particularly in the zonular fibers and lens. Traditional ocular models, relying on spherical or Cartesian coordinate systems, are unable to fully capture the intricacies of the eye’s anatomy, leading to inaccuracies in force distribution, intraocular pressure (IOP) calculations, and surgical planning.
Purpose of Research
This research introduces a novel curvilinear coordinate system designed to more accurately represent the eye’s biomechanical forces, particularly focusing on the zonular fibers and their role in lens accommodation and movement. The aim is to advance the understanding of the eye's internal mechanics to improve surgical interventions, such as cataract surgery, and influence the development of new treatments for ocular conditions like myopia, presbyopia, and glaucoma.
Contributions of This Work
The primary contribution is the development of the Zonular Coordinate System (ZCS), which utilizes Generative AI for rapid exploration of potential ZCS configurations and Finite Element Analysis (FEA) for physics-based validation of the model. This methodology improves the accuracy of biomechanical modeling in ocular diagnostics and treatments, advancing the fields of ophthalmology and biomedical engineering.
Methodology
The study combines high-resolution ocular imaging with advanced biomechanical modeling techniques. Generative AI is used to explore multiple configurations of the ZCS, while FEA is employed to simulate intraocular forces, zonular tension, and lens movement under various physiological conditions. This integration allows for the refinement of the ZCS to optimize both accuracy and efficiency.
Preliminary Results
Preliminary findings show that the ZCS is highly effective in predicting force distributions within the eye, especially in the zonular fibers and lens. The curvilinear coordinate system accurately models lens accommodation and the dynamic behavior of the ciliary body, providing valuable new insights into the mechanics of the eye.
Conclusions
The adoption of the ZCS marks a significant advancement in ocular biomechanics. By more accurately modeling the eye’s complex anatomy, this research can improve clinical applications, especially in surgical planning and treatments for conditions such as glaucoma and cataracts. The ZCS approach has the potential to enhance both diagnostics and therapeutics in ophthalmology, leading to better patient outcomes.
The integration of the Zonular Coordinate System (ZCS) with Generative AI and Finite Element Analysis (FEA) marks a significant advancement in simulating the eye’s complex structures with greater precision. This innovative approach offers promising improvements in clinical applications, including surgical planning and treatments for conditions such as glaucoma.
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