Ophthalmic Microcannula Assembly for Controlled Viscoelastic Injection
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Solution Overview
Problem
Existing ophthalmic devices struggle to precisely deliver small amounts of viscous fluids, such as viscoelastic materials, through small bore needles or microcannulas during delicate surgical procedures, particularly in ophthalmic surgeries like cataract and glaucoma, due to the difficulty in controlling flow and maintaining consistent pressure.
Innovation Solution
The development of an ophthalmic device with a positive displacement mechanism and a composite microcannula design that includes reinforcing elements and a signaling beacon, allowing precise control of viscous fluid delivery and navigation through small tissue spaces, such as Schlemm's Canal, with features like pressure regulation and flexible yet stiff properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a small bore needle or microcannula is used to inject viscous fluid, then the device can navigate through small tissue spaces, but the flow control and pressure consistency deteriorate
Solution Approach 1:
The device employs a positive displacement mechanism with incremental actuation capability that dynamically adjusts fluid delivery. The mechanism includes a plunger with stops at predetermined positions, allowing the operator to advance the plunger in controlled increments to deliver precise volumes of viscous fluid through the small bore needle, thereby maintaining flow control despite the narrow delivery pathway
Solution Approach 2:
The device changes the physical parameter of fluid delivery by using a positive displacement mechanism that converts rotational motion of a threaded rod into linear motion of the plunger. This mechanical transformation allows precise control over the volume and rate of fluid delivery, maintaining consistent pressure and flow rates even through small bore needles with limited flow capacity
2Manufacturing precision
If a positive displacement mechanism is used to control viscous fluid delivery, then flow precision is improved, but device complexity increases
Solution Approach 1:
The positive displacement mechanism is segmented into discrete functional components: a threaded rod for actuation, a plunger with predetermined stops at specific positions along its length, and a syringe barrel. These segmented elements work together to provide incremental fluid delivery control, where each stop represents a predetermined volume milestone, simplifying the control interface while maintaining precision
Solution Approach 2:
The plunger acts as an intermediary element between the actuation mechanism (threaded rod) and the viscous fluid. The plunger translates rotational actuation into linear displacement, and its predetermined stops provide tactile feedback and volume reference points, mediating the complex interaction between operator input and fluid delivery to achieve precise control
3Strength
If reinforcing elements are added to the microcannula, then structural strength is improved, but flexibility deteriorates
Solution Approach 1:
The microcannula employs local quality by placing reinforcing elements (such as braided wires or mesh) only in specific regions where structural support is most needed, such as the proximal shaft portion. The distal tip and intermediate sections maintain thinner wall construction to preserve flexibility for navigation through tortuous tissue paths, achieving optimal balance between strength and adaptability through spatially differentiated structural properties
4Measurement precision
If a signaling beacon is added to the microcannula, then navigation capability is improved, but device complexity increases
Solution Approach 1:
The signaling beacon utilizes optical properties (such as fluorescence, phosphorescence, or reflective characteristics) that cause the distal tip or specific portions of the microcannula to emit or reflect light at characteristic wavelengths. This optical signaling allows precise visualization and tracking of the cannula tip location under appropriate illumination, enhancing navigation capability through biological tissue without requiring complex electronic sensors or actuators
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 and controlled delivery of viscous fluids, minimizing tissue trauma and ensuring accurate placement of surgical tools and materials, particularly in ophthalmic surgeries, by providing incremental and consistent flow rates and maintaining pressure.
Implementation Method 1
Due to the unusual shear thinning or thixotropic properties of such materials, viscoelastics are injectable through a small bore needle or cannula, then recoil to a material providing stiff gel-like properties after injection
Implementation Method 2
Due to the unusual shear thinning or thixotropic properties of such materials, viscoelastics are injectable through a small bore needle or cannula, then recoil to a material providing stiff gel-like properties after injection
Data Source
AI summary
Ophthalmic devices include a housing and a cannula extending from the housing, the cannula having a lumen for fluid flow, a reservoir for holding fluid and an activation assembly. The activation assembly includes a rotatable wheel and a moveable housing ring coupled to the wheel, the coupled rotatable wheel and moveable housing ring configured to move inward together towards an interior of the housing when an inward force is applied to the wheel and to move outward together away from the interior of the housing when an outward force is applied to the coupled wheel and the moveable housing ring. Methods of operating ophthalmic devices are also provided.