Curved Needle for Subretinal Drug Delivery
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Solution Overview
Problem
Macular degeneration poses a significant challenge due to the difficulty in accessing the macula, which is located at the back of the eye and underneath the delicate layer of the retina, making it hard to deliver therapeutic substances effectively in a highly localized fashion.
Innovation Solution
The development of an apparatus that allows for the subretinal administration of therapeutic agents from a suprachoroidal approach, utilizing a flexible cannula and a needle that can be advanced to pierce the choroid without penetrating the retina, enabling direct delivery to the subretinal space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a needle is advanced to pierce the choroid from a suprachoroidal approach, then therapeutic agents can be delivered directly to the subretinal space, but there is a risk of penetrating the retina and causing retinal perforation
Solution Approach 1:
The needle is pre-bent at a specific angle (e.g., 30-45 degrees) relative to its longitudinal axis, creating a curved configuration that allows it to pierce the choroid and enter the subretinal space without continuing in a straight line that would penetrate the retina. The curvature radius and angle are specifically designed to achieve the desired trajectory and stop at the subretinal layer.
Solution Approach 2:
The needle has different properties at different locations: the distal portion is sharp for piercing the choroid, while the proximal portion is blunt to prevent retinal perforation. The needle also has a pre-bent configuration at specific locations to control the penetration trajectory and ensure termination at the subretinal space without advancing further into the retina.
2Ease of operation
If a straight needle is used to access the subretinal space, then the needle can be easily controlled and advanced, but it is difficult to reach the macula at the back of the eye without penetrating the retina
Solution Approach 1:
The needle incorporates a pre-bent curved section that provides the necessary trajectory change to reach the posterior macula region. The curvature radius and angle are optimized to navigate the anatomical path from the injection site to the subretinal space at the macula, enabling precise delivery without requiring complex manual manipulation.
3Force
If a sharp needle is used to pierce the choroid, then penetration is easier and requires less force, but it increases the risk of uncontrolled advancement and retinal perforation
Solution Approach 1:
The needle exhibits spatially varying properties: the distal tip is sharp to minimize penetration force for choroid puncture, while the proximal shaft is blunt to provide tactile feedback and prevent excessive advancement. This gradient in sharpness allows easy choroid penetration while inherently limiting penetration depth to avoid retinal perforation.
Solution Approach 2:
The pre-bent configuration creates a natural stop point where the needle's curvature causes it to exit the choroid and enter the subretinal space, then bend away from the retina. This geometric constraint provides passive safety by preventing continued forward motion that would cause retinal perforation, even if excessive force is applied.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An apparatus includes a body, a cannula (50), and a needle (100). The cannula is flexible and extends distally from the body. The needle is slidably disposed in the cannula. The needle includes a sharp distal tip (102) and a curved portion. The needle is configured to translate relative to the cannula between a proximal position and a distal position. The distal tip is configured to be positioned inside the cannula when the needle is in the proximal position. The distal tip is configured to be positioned outside the cannula when the needle is in the distal position. The needle is resiliently biased to extend along a curve through the curved portion.