intraocular robotic surgery: cataract removal and retinal
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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.
2/15/2021 4
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
2/15/2021 6
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
2/15/2021 8
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
2/15/2021 10
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
2/15/2021 11
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
2/15/2021 13
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
2/15/2021 14
Lens Extraction: Selective Targeting
Anatomical
Modeling
Trajectory
Generation
Lens
Extraction
Progress
Assessment
Robot-to-Eye
Alignment
2/15/2021 15
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
2/15/2021 16
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
2/15/2021 18
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
2/15/2021 19
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
2/15/2021 21
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
2/15/2021 24
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
2/15/2021 26Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
mp4
2/15/2021 27
1. Vein Approach: Implementation
2/15/2021 27Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
WMV
2/15/2021 28
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
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
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
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
2/15/2021 33Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
mp4
2/15/2021 34
3. Vein Cannulation: Implementation
2/15/2021 34Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
WMV
2/15/2021 35
3. Vein Cannulation: Implementation
2/15/2021 35Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
mp4
2/15/2021 36
3. Vein Cannulation: Implementation
2/15/2021 36Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
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
2/15/2021 41Mechatronics and Controls Laboratory, Mechanical and Aerospace Engineering Department, UCLA
Contact
Matthew J. Gerber, PhD
Postdoctoral Scholar-Fellow
Lab Phone: (310) 206-4449
gerber211@ucla.edu
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.
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