intraocular robotic surgery: cataract removal and retinal

Intraocular Robotic Surgery:

Cataract Removal and Retinal Vein Cannulation

Matthew J. Gerber, PhD

2020-02-06

Postdoctoral Scholar-Fellow in

Advanced Robotic Eye Surgery (ARES) Laboratory and

Mechatronics and Controls Laboratory, UCLA

2/15/2021 2Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA

Acknowledgments

Mechatronics and Controls Laboratory:

Cheng-wei Chen (PhD)

Yu-Hsiu (Martin) Lee (PhD)

Kenneth Vuong (UG)

Jessica Chen (UG)

Stein Eye Institute:

Andrea Govetto (MD)

Anibal Francone (MD)

Ismaël Chehaibou (MD)

Moritz Pettenkofer (MD)

Mercedes Rodriguez (MD)

Funding Sources

• National Institutes of Health

R21 EY024065-02

R01 EY029689-01, R01 EY030595-01

T32 EY7026-43

• The Hess Foundation, New York, NY

• The Earl and Doris Peterson Fund, Los Angeles, CA

• Research to Prevent Blindness (RPB), New York, NY

• Kairos Venture Gift Campaign, Pasadena, CA

• Department of Mechanical and Aerospace Engineering

Internal Funding

UD: Undergraduate

Current Participants

2/15/2021 3

Intraocular Robotic Interventional Surgical System (IRISS)

• Originally developed for wide range of anterior

and posterior segment surgical procedures

Cataract extraction

Vitreoretinal surgery

• Capabilities include:

Mounts any commercially available tool

o Five DOF and large range of motion

Simultaneous use of two surgical instruments

o Fast exchange between mounted tools

o Two pivot points in close proximity

1. Rahimy, E., et al. "Robot-assisted intraocular surgery: development of the IRISS and feasibility studies in an animal model." Eye 27.8: 972-978, 2013.

2. JT Wilson, et al., “Intraocular robotic interventional surgical system (IRISS): Mechanical design, evaluation, and teleoperated manipulation.” The International J. of Medical Robotics and Computer Assisted Surgery, 14(1):e1841, 2018.

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Teleoperation Procedures and Accomplishments

Procedures:

• Anterior lens capsulorhexis

• Viscoelastic injection

• Hydrodissection

• Lens aspiration

• Retinal vein cannulation

• Vitrectomy

Accomplishments:

• First robotic system to create

a round, curvilinear capsulorhexis

• First (and only) to perform an entire

lens extraction (start to finish)

1. Rahimy, E., et al. "Robot-assisted intraocular surgery: development of the IRISS and feasibility studies in an animal model." Eye 27.8: 972-978, 2013.

2. JT Wilson, et al., “Intraocular robotic interventional surgical system (IRISS): Mechanical design, evaluation, and teleoperated manipulation.” The International J. of Medical Robotics and Computer Assisted Surgery, 14(1):e1841, 2018.

Partially Automated Cataract Extraction

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Partially Automated Cataract Extraction: Background and Motivation

• Cataract Surgery

Cataracts represent a leading cause of blindness worldwide [1]

20 million surgeries performed every year [2]

Common complications:

o Incomplete cataract removal (1.1%) [3]

o Posterior capsule (PC) rupture (1.8–4.4%) [3]

1. Donatella Pascolini and Silvio Paolo Mariotti. “Global estimates of visual impairment: 2010.” British J. of Ophthalmology, 96(5):614–618, 2012.

2. National Eye Institute. “Facts About Cataract.” Last accessed: 11/16/2017.

3. P. Desai, D.C. Minassian, and A. Reidy, “National cataract surgery survey 1997–8: a report of the results of the clinical outcomes.” British J. of Ophthalmology, 83(12):1336–1340, 1999.

4. https://www.myalcon.com/professional/cataract-surgery/cataract-equipment/lensx-laser-system

LenSx Femtosecond Laser System [4]

2/15/2021 7

System Architecture and Setup: The IRISS

CAD Model of System

System Modifications [1,2]

• Single arm mechanism, single tool: I/A handpiece

• Integration of optical coherence tomography (OCT) probe

1. C.W. Chen, et al., “IRISS: Semi‐automated OCT‐guided cataract removal.” Medical Robotics & Computer Assisted Surgery (2018).

2. C.W. Chen, et al., “Semiautomated OCT-Guided Robotic Surgery for Porcine Lens Removal,” Cataract & Refractive Surgery (2019).

System Architecture

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Optical Coherence Tomography (OCT)

OCT Overview

• Noninvasive optical imaging technique

• Light equivalent to ultrasound

• OCT data consists of structural information of target sample

Laser light backscattered from sample material

• Provides depth information (cameras do not)

Human Eye

Source: reviewofophthalmology.com

OCT-Generated Images (B-scans)

~250 µm

~24 mm

OCT Scanning RangeOCT System

ThorLabs Telesto-II 1060 nm SD-OCT with LSM04 lens

• Embedded 2D camera and motorized Z-axis (±30 mm)

• 3D volume scans in the range of 10 x 10 x 9.4 mm

Radial resolution: 25 µm (𝑿𝑂 and 𝒀𝑂)

Axial (depth) resolution: 9.4 µm (𝒁𝑂)

• Acquisition rates:

Volume scan: 40 s (0.025 Hz)

B-scan: 0.1 s (10 Hz)

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Prototype Setup

Pig Eye

Model

OCT

I/A Handpiece

The IRISS

GUI

Control

Software

Phaco

System

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Registration and Alignment

• Coordinate transformation between the robot and the OCT frame determined

• Corneal incision detected and modeled

• Tool-insertion trajectory generated

Anatomical

Modeling

Trajectory

Generation

Lens

Extraction

Progress

Assessment

Robot-to-Eye

Alignment

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Eye Anatomy

Segmentation and Modeling of Anatomical Structures

Cornea

Lens material

Iris

Iris

(inverted)

Posterior capsule

Posterior

Capsule

Iris

Cornea

OCT Volume Scans

Reconstructed Anatomical Model

1

2

3

Lens

Anatomical

Modeling

Trajectory

Generation

Lens

Extraction

Progress

Assessment

Robot-to-Eye

Alignment

1

2

3

4

4

4

3

2

1

5

2/15/2021 12

Tool-tip Trajectory Generation

Safety

Margins

Cornea

Iris

Posterior

Capsule

Side View Top View

Anatomical

Modeling

Trajectory

Generation

Lens

Extraction

Progress

Assessment

Robot-to-Eye

Alignment

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Automated Lens Extraction: Trajectory Following

• Automated lens extraction assessed by surgeon in real-time

• Override commands provided, if necessary

• “Point and click” allows for surgeon to aspirate specific targets

Anatomical

Modeling

Trajectory

Generation

Lens

Extraction

Progress

Assessment

Robot-to-Eye

Alignment

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Lens Extraction: Selective Targeting

Anatomical

Modeling

Trajectory

Generation

Lens

Extraction

Progress

Assessment

Robot-to-Eye

Alignment

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OCT-Based Intraoperative Evaluation

2 min 4 min Completed

Anatomical

Modeling

Trajectory

Generation

Lens

Extraction

Progress

Assessment

Robot-to-Eye

Alignment

• Trajectory paused every two minutes for surgeon assessment via OCT volume scan

If material remains, trajectory continued

If only small particles remain, surgeon can specifically target them

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System Evaluation: Animal Model Trials

Post-op

Complete Lens Extraction

Post-op

Incomplete Lens Extraction

• Performed lens extraction on 30 ex-vivo pig eyes

Averaged completion time: 4:37 ± 0:42 s

No posterior capsule rupture

Complete lens extraction in 25 trials

Small (≤ 1 mm3) pieces remained in 5 trials

Postoperative Evaluation Metrics

Partially Automated Retinal Vein Cannulation

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Surgical Motivation: Retinal Vein Occlusion (RVO)

Definition

• Occlusion (e.g., blood clot) of a retinal vein

Consequences

• Vitreous hemorrhage (blood on retina)

• Glaucoma (optic nerve damage)

• Macular edema (retinal swelling)

Frequency

• Second most common cause of vision loss due to retinal vascular disease [1]

• Prevalence rate of 0.5–2.0% in the U.S. [1]

Treatment Options

• Steroids and laser ablation may help treat symptoms

• There is no cure — removing the occlusion is currently infeasible

1. M. Laouri, et al. "The burden of disease of retinal vein occlusion: review of the literature," Eye (2011).

3. Modified from: https://www.allaboutvision.com/conditions/eye-occlusions.htm

4. S.S. Hayreh, et al. "Fundus changes in branch retinal vein occlusion," Retina (2015).

Optic Disc

Retinal Vein

Occlusion

Vitreous

Hemorrhage

Fovea

Macula

[3]

Microscope View of Retina with Vitreous Hemorrhage

[2]

Occlusion

Retinal Vein Occlusion

Lumen

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Background: Retinal Vein Cannulation (RVC)

Retinal Vein Cannulation

• A potential cure for retinal vein occlusion

Procedure

• Vein cannulated with micropipette

• Anticoagulant infused through vein at site of obstruction

Anticoagulant is expensive ($6,400 per 100 mg vial) [1]

Retinal Vein

(Ø120–200 µm) [2]

Occlusion

Micropipette

RETINA CROSS SECTION

Anticoagulant

1. D. Kleindorfer, et al. "Cost of Alteplase has more than doubled over the past decade," Stroke (2017).

2. Y. Ouyang, et al. “Retinal vessel diameter measurements by SD-OCT,” Clinical and Experimental Ophthalmology (2015).

2/15/2021 20

Problem Statement

Objective:

To develop a method to guarantee vein access and successful infusion during RVC.

Main Physiological Challenges:

1. Accurate positioning of micropipette to access vein

Lateral (XY) positioning and depth (Z) positioning

Retinal vein diameter: ~120–200 µm [1]

Human hand tremor: ~200–350 µm [2]

2. Uncertainty of micropipette depth due to limited resolution of depth perception

Only indirect cues of tool depth (e.g., shadows and color changes)

3. Substantial cognitive load on surgeon due to complexity and stress of sensing,

guidance, and decision making

Safely guide micropipette, avoid collateral damage, accurately access vein,

maintain fixed pivot point, choose when to infuse…

Solution: Use robotic system with OCT feedback and automated procedures.

1. Y. Ouyang, et al. “Retinal vessel diameter measurements by SD-OCT,” Clinical and Experimental Ophthalmology (2015).

2. C.N. Riviere, et al. “Characteristics of hand motion of eye surgeons,” Engineering in Medicine and Biology (1997).

Desired

Cannulation Site

~24 mmPivot Point

(Surgical Incision)

Cross-section of Human Eye

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System Architecture and Setup: Micropipette

CAD Model of System

Glass Micropipette (B100-58-80, Clunbury Scientific LLC)

Micropipette Holder

Alignment

Mechanism

~60 mm

1

1

Vitrectomy Machine

(Alcon ACCURUS)

Glass Micropipette (Ø80 µm)

• Embedded in stainless steel tube (Ø1.50 µm)

• Tygon tubing connects viscous fluid control (VFC) line of

vitrectomy machine; controllable infusion pressure (0–80 psi)

2/15/2021 22

Custom Retinal Vein Phantom

Fabrication Process

• Simple (7 steps), fast (20 minutes plus cure time), customizable vein diameters (Ø120–200 µm)

1. Y. Wang, et al. “Pilot study of OCT measurement of retinal blood flow in retinal and optic nerve diseases,” Investigative Ophthalmology & Visual Science (2011).

Al Mold Cleaned Wire Inserted Substrate Added Wire Removed Phantom Removed Vein Filled

Embedded

Wire

Substrate

(Silicone)

Mold for Fabrication of Phantoms

Mold

• Reusable, three at a time

CURED

OCT Appearance

In Vivo

Human [1]

Developed

Phantom

Re

tina

Vein

SIDE VIEWS

Complete Phantom

Dimensions

• Circular cross section, Ø120–200 µm

2/15/2021 23

Technical Approach Overview

𝑂𝒑𝐶

{OCT}

𝒑𝑅𝐶𝑀{IRISS}

~60° 𝒑𝑖

𝒑𝑆𝐼

(3) Vein Cannulation

𝑂𝒑𝐶

{OCT}

{IRISS}

(2) Vein Targeting

𝑂𝒑𝐶

{IRISS}

{OCT}

𝑂𝒑𝐶

𝒑𝑖

{IRISS}

{OCT}

𝒑𝑅𝐶𝑀=𝒑𝑆𝐼

(1) Vein Approach

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Camera View

1. Vein Approach: Modeling of Retinal Vein Phantom

1. Camera view displayed for selection of cannulation site, 𝑂𝒑𝐶2. Localized B-scans processed to determine vein centers

3. Model of vein constructed and used for duration of procedure

640 px ≈ 13.6 mm

48

0 p

x≈ 1

0.2

mm

1.5

mm 3.0 mm

Example B-Scan Region of

Interest

Region of

Interest

Modeled Vein {OCT}

x [mm]y [mm]

z [

mm

]

𝑂𝒑𝐶

Retinal Vein Phantom

2/15/2021 25

x [mm]

y [mm]

z [

mm

]

Planned Trajectory

{IRISS}

Virtual

Sclera60°

𝒑𝑖

𝒑𝑆𝐼

𝐼𝒑𝐶

𝒑𝑅𝐶𝑀

1. Vein Approach: Trajectory Generation

Error Contribution to Calculate 𝜆

Registration Stage Sum

Mean 190.0 5.4 195.4

Std. 77.1 4.1 81.2

Max. 340.6 15.8 356.4

* All values in units of µm

𝜆 ≥𝑟𝑒

cos 30°≈ 411.5 µm

𝑟𝑒 = 356.4 µm

𝑂𝒑𝐶

𝒑𝑖 𝜆

~300 µm

𝑟𝑒 30°

𝒑𝑅𝐶𝑀 = 𝒑𝑆𝐼

60°

{OCT}

x

z

𝑂𝒑𝐶

𝒑𝑖𝜆

~300 µm

• Insertion trajectory planned from vein model

1. XYZ stage motion such that 𝒑𝑅𝐶𝑀 = 𝒑𝑆𝐼

2. Joint angles 𝜃1 , 𝜃2, and 𝑑3

• Accounting for accumulated error with definition of 𝒑𝑖

2/15/2021 26

1. Vein Approach: Implementation


mp4

2/15/2021 27

1. Vein Approach: Implementation


WMV

2/15/2021 28


𝑂𝒑𝐶

{OCT}


~60° 𝒑𝑖

𝒑𝑆𝐼


𝑂𝒑𝐶

{OCT}

{IRISS}

(2) Vein Targeting

𝑂𝒑𝐶

{IRISS}

{OCT}

𝑂𝒑𝐶

𝒑𝑖

{IRISS}

{OCT}


(1) Vein Approach

2/15/2021 29

2. Vein Targeting: Centerline Detection

Example B-Scan (out of 400)

x [px]

Custom B-Scan

Tool Top

(Steel)

Glass

Micropipette

Edge Detection

• Tool centerline detection from single volume scan

Top View (𝜃2) Side View (𝜃1)

Detected

Centerline

Detected

Tool Tip

2/15/2021 30

2. Vein Targeting: Implementation

• Error is cancelled by actuating first two robotic joints, 𝜃1 and 𝜃2• Upon completion, tool “points at” cannulation site to within 20 µm (micropipette Ø80 µm cf. vein Ø120 µm)

2/15/2021 31


𝑂𝒑𝐶

{OCT}


~60° 𝒑𝑖

𝒑𝑆𝐼


𝑂𝒑𝐶

{OCT}

{IRISS}

(2) Vein Targeting

𝑂𝒑𝐶

{IRISS}

{OCT}

𝑂𝒑𝐶

𝒑𝑖

{IRISS}

{OCT}


(1) Vein Approach

2/15/2021 32

3. Vein Cannulation: Augmented OCT Feedback

• Surgeon decides:

In/out motion to control tool depth (1 DOF)

When to infuse

• Initial tip overlay from OCT volume scan (9.4–25 µm)

Subsequent overlays via encoder feedback (10 µm)

Surgeon can account for vein compression/movement

Tool tip visualized when hidden inside retina

OCT Feedback during Cannulation (10 Hz)

Depth Resolution: 9.4 µm

B-scan Plane

Camera View

Example of Successful Cannulation

2/15/2021 33

3. Vein Cannulation: Implementation


mp4

2/15/2021 34



WMV

2/15/2021 35



mp4

2/15/2021 36



WMV

2/15/2021 37

• n = 30 trials on Ø120, Ø160, and Ø200 µm vein phantoms

• 100% successful infusion in all trials (successful cannulation)

• Total trial time: 10:01 (minimum: 7:25; maximum: 15:23)

• Surgical complications: 3

Experimental Results

Sub-retinal bleb formation (Tool too deep)

Ø120 µm

Reflux (Tool too shallow)

Ø160 µmØ120 µm

Reflux (Tool too shallow)

• Main challenge is successfully piercing the vein due to resiliency of silicone phantom

Deficiency of retinal vein phantom—not the developed system

Reflux Sub-Retinal Bleb n

Ø120 µm 1 1 10

Ø160 µm 1 0 10

Ø200 µm 0 0 10

1. Gijbels, et al. "In-Human Robot-Assisted Retinal Vein Cannulation, A World First." Annals of Biomedical Engineering (2018).

2. M. de Smet, et al. "Release of experimental retinal vein occlusions by direct intraluminal injection of ocriplasmin." British Journal of Ophthalmology (2016).

3. Y. Sungwook, et al. "Manipulator design and operation of a six-degree-of-freedom handheld tremor-canceling microsurgical instrument," IEEE Transactions on Mechatronics (2015).

2/15/2021 38

Additional Retinal Microsurgery: Sub-retinal Injection

• n = 3 trials; 100% successful bleb formation

mp4

2/15/2021 39

Additional Retinal Microsurgery: Sub-retinal Injection

• n = 3 trials; 100% successful bleb formation

WMV

2/15/2021 40

Conclusions and Future Work

Cataract Extraction:

• Developed several automated steps of robotic lens extraction

Anatomical modeling

Lens-extraction trajectory generation

Tool-tip trajectory tracking

• Evaluated the system by performing lens extraction on 30 ex-vivo pig eyes

• Future Work:

Visualize lens equator, stabilize anatomy, and pursue fully automated lens extraction

Retinal Vein Cannulation:

• Accurate vein targeting (≤ 20 µm) despite large (~300–400 µm) robotic uncertainties

• High-resolution knowledge of tool depth (9.4–25 µm) via augmented OCT feedback (10 Hz) during cannulation

• Simplification of vein access to a single-DOF and single-decision problem for the surgeon

• Future Work:

Automated, localized tracking of vein (to account for vein deformation and/or patient movement)

Advance to more realistic eye phantoms: Ex vivo and in vivo pig eyes


Contact

Matthew J. Gerber, PhD

Postdoctoral Scholar-Fellow

Lab Phone: (310) 206-4449

[email protected]

Advanced Robotic Eye Surgery (ARES) Laboratory

uclahealth.org/eye/center-for-advanced-robotic-eye-surgery

Stein Eye Institute, Department of Ophthalmology, UCLA

A-231 Jules Stein Eye Institute

Los Angeles, CA 90095

Mechatronics and Controls Laboratory

http://www.maclab.seas.ucla.edu/

Department of Mechanical and Aerospace Engineering, UCLA

1540 Boelter Hall

Los Angeles, CA 90095

Thank you for your attention.

intraocular robotic surgery: cataract removal and retinal

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