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Development of Cutting Edge Instrumentation for Vision Preserving Surgery

Hans Chen, Joanne Low, Quinn Mullineaux, Hanieh Seilsepour

Department of Mechanical and Aerospace Engineering at University of California San Diego

Sponsored by Dr. Bobby Korn, MD PhD

Overview

The sponsored project led by Dr. Korn from the Shiley Eye Institute focuses on advancing instrumentation for vision-preserving surgery, particularly in the realm of Optic Nerve Sheath Fenestration (ONSF). ONSF entails the delicate dissection through orbital fat pads to access the optic nerve, situated at the posterior of the eye. This procedure aims to alleviate pressure buildup caused by excess fluid by creating a small incision in the optic nerve. The project's primary objective is to streamline and simplify the surgical process by developing a specialized surgical device, thereby reducing the need for multiple tools and minimizing procedural complexity and manpower requirements.

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Figure 1: Step-by-step illustration of ONSF [1]

Impact on Society and Safety

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  • Enables completion of more operations annually with only one surgeon needed
  • Refined tool geometry reduces risk of damage to neighboring vital structures and orbital bleeding
  • Incorporation of fiber optic light source improves visibility and procedure ease
  • Overall advancements in ONSF enhance accessibility, safety, and efficiency of the procedure

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Acknowledgements

We would like to thank the following people for their help and expertise:

  • Dr. Bobby Korn & Eman Eman Al-Sharif from the Shiley Eye Institute
  • Prof. Jerry Tustaniwskyj & Prof. David Gillett
  • Ian Richardson & Thomas Chalfant from the MAE Machine Shop

References

[1] Xue, X., Zhou, C., Gao, Y., Ji, X., & Zhang, X. “Optic nerve sheath fenestration for visual impairment in cerebral venous diseases.” Frontiers in Neurology, 2023, https://www.frontiersin.org/articles/10.3389/fneur.2023.1065315/full

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Hardware Performance

Tool Testing Parameters:

  • Tested in cadaver lab to closely mimic in vivo surgery

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Testing Feedback:

  • Only two tools are required to successfully facilitate access to the optic nerve
  • Number of additional nurses required for operation reduced from two down to one
  • Notch is able to successfully isolate optic nerve for surgical procedure

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Figure 8: Tool tested on 3D printed anatomically accurate skull model

Structural Analysis

  • Theoretical max load during operation: 12N
  • Static structural simulation ran in Ansys

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Figure 6: Ansys static load simulation with max load of 12N applied

  • The analysis confirmed that the tool can withstand the maximum force applied during ONSF operation.

Future Improvements

  • Implement an actuator to allow variable fat retraction
  • Add a switch to adjust the brightness for light source
  • Add a scope to help locate the optic nerve
  • Use a snap-fit mechanism
    • Reusable stainless steel handle (item 1)
    • Disposable biocompatible resin head (item 2)
    • Insert item 1 into item 2
    • Perform the ONSF surgery
    • Detach the head (item 2)
    • Sterilize the handle (item 1) for next procedure

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Figure 2: Final tool manufactured from 316L stainless steel

Final Tool Design

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  • Able to retract orbital tissue to gain access to the optic nerve by facilitating retraction of fat between the orbital bone and eyeball
  • Two versions of this tool are designed:
  • Reusable single component tool made out of 316L stainless steel
  • Disposable single component tool made out of biocompatible resin with a circular channel for fiber optic implementation

Key Features and Components

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Tool Handle

  • Made from 316 stainless steel
  • Sterilizable
  • 60 degree bend to optimize visibility and grip angle

Figure 3: CAD model illustrating the final design of the tool, featuring a metal version that is reusable and sterilizable.

Tool Head

  • Curvature mimics eyeball such that tool can fit within small geometry and effectively retract surrounding fat pads
  • Scooped notch in head of tool is designed to easily isolate optic nerve

Fiber Optic Light Source

  • Illuminates area of focus for surgeon to aid in locating optic nerve
  • Fiber optics are autoclave sterilizable
  • Battery and LED light source component are detachable and easily re-attachable to fiber optic component
  • Battery lifetime is much greater than the length of the surgery

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Figure 4: CAD model of final tool head design

Figure 9: Two-component tool with detachable head

Figure 5: Implementation of fiber optic light source

Notch for optic nerve isolation

Figure 7: Showcasing the tool's internal components, including the fiber optic rod, battery, and circuitry for power

Tool Handle

Item 1

Item 2