Shape-Memory Pupil Expander for Stable Hook-Free Iris Dilation
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Solution Overview
Problem
Existing pupil expanders for cataract surgery often require positioning hooks that can cause iris damage and lack structural integrity, necessitating a stable, shape-maintaining device that can be applied without additional tools.
Innovation Solution
A pupil expander constructed of a shape-memory nitinol frame covered by an elastomer, which unfolds to expand the pupil upon injection, minimizing iris contact and maintaining stability during surgery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If positioning hooks are used to place the pupil expander into position, then the device can be securely positioned on the iris, but the hooks may overstretch and damage the iris
Solution Approach 1:
The patent removes the positioning hooks from the device entirely. The pupil expander is designed to be self-positioning through its elastic memory properties, eliminating the harmful hooks while maintaining reliable positioning capability through the natural elastic recovery of the nitinol frame when engaged with the iris tissue.
Solution Approach 2:
The pupil expander uses its own elastic memory properties to achieve positioning without external hooks. The nitinol frame automatically returns to its pre-formed circular shape after compression, using its inherent elastic energy to engage with and position itself on the iris tissue, making the device self-positioning and eliminating the need for separate positioning instruments.
2Ease of operation
If the pupil expander is made entirely of soft polymers, then the device can be easily applied, but it lacks sufficient structural integrity to maintain a stable pupil size and shape during surgery
Solution Approach 1:
The patent employs a composite structure combining nitinol (a shape memory alloy) with an elastomeric polymer coating. The nitinol frame provides the necessary structural integrity, shape stability, and elastic memory properties, while the elastomer coating ensures biocompatibility and smooth interaction with iris tissue, achieving both ease of application and stable pupil maintenance.
Solution Approach 2:
The nitinol frame undergoes a phase transformation from austenite to martensite during compression, allowing the device to be deformed into a compressed state for injection. After injection, the material transforms back to austenite, recovering its original circular shape and providing the structural stability needed to maintain pupil size and shape during surgery.
3Stability of the object's composition
If the pupil expander is made rigid, then it can maintain stable shape and size during surgery, but it cannot be folded for insertion into a tubular applicator
Solution Approach 1:
The nitinol frame exploits phase transformation between austenite and martensite states to change its mechanical properties. In the martensite state, the material is soft and flexible, allowing the frame to be folded and compressed for injection. After deployment, it transforms to the austenite state, becoming rigid and maintaining its stable circular shape to hold the pupil open during surgery.
Solution Approach 2:
The device transitions from a static rigid structure to a dynamic system that changes its mechanical properties in response to temperature and stress conditions. The nitinol frame dynamically adjusts between flexible and rigid states, enabling both easy insertion when compressed and stable shape maintenance when deployed, without requiring complex folding mechanisms.
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 device ensures stable pupil expansion without iris damage by using a shape-memory frame and elastomer covering, allowing tool-free application and smooth deployment.
Implementation Method 1
a frame formed of material having shape-memory characteristics, the frame being in the form of two arc-shaped sections connected together at one end to form a broken circle
Implementation Method 2
The covering is preferably formed of an elastomer, which has suitable elasticity and a smooth surface, so that application of the device to the iris minimizes friction between the device and the edges of the iris
Data Source
AI summary
A pupil expander is formed from a frame of shape-memory material with a covering made of elastomer. The frame is in the form of two arc-shaped sections connected together at one end to form a broken circle having free distal ends. Each arc-shaped section has an upper frame portion and a lower frame portion connected to each other at the distal ends thereof. The covering is disposed over each arc-shaped section and has a C-shaped cross section so as to form an outwardly facing groove between the upper frame portion and the lower frame portion. The pupil expander is configured to be folded in half with the grooves facing each other and straightened so as to form a cylindrical body for insertion into a tubular applicator and upon release from the applicator, the pupil expander resumes the shape of the broken circle to push the margins of the pupil wider.