ORIGINAL STUDY
`
`K-RIM (Corneal Rim) Angle Surgery Training Model
`Anish Arora,* Samir Nazarali, BHSc,† Lauren Sawatzky, MD,‡
`Malcolm Gooi, MD,§ Matt Schlenker, MD, FRCSC,∥
`Ike K. Ahmed, MD, FRCSC,∥ and Patrick Gooi, MD, FRCSC§
`
`Purpose: To develop an angle surgery training model for training an
`array of microincisional glaucoma surgery (MIGS) procedures.
`Methods: We describe a method for preparing an angle surgery
`training model using human cadaveric corneoscleral rims. The
`model provides realistic tactile tissue simulation and excellent angle
`visualization requiring bimanual technique. Corneoscleral rims may
`be used multiple times and are prepared at low cost, allowing for a
`high volume of practice surgeries.
`Results: This model allows for practice in bimanual surgical training
`using the gonioscopy lens for visualize alongside surgical tools. The
`in vivo surgical conditions and limited tactile feedback are recreated
`using human cadaveric eyes which nonhuman models fail to pro-
`vide. Our model is prepared at low cost, with relative ease and also
`provides appropriate positioning of Schlemm canal and for high
`volume of practice as the canal can be used in 90-degree segments.
`Conclusions: Few angle surgery training models currently exist and
`none provide these necessary features. The model presented here
`aims to meet the growing demand for adequate training models
`required for technically advanced MIGS techniques.
`Key Words: glaucoma, training model, minimally invasive glau-
`coma surgery, bimanual technique, corneoscleral rims
`(J Glaucoma 2019;28:146–149)
`
`G laucoma surgery is rapidly advancing as many new
`
`microincisional glaucoma surgery (MIGS) devices are
`being developed including the FDA approved iStent Tra-
`becular Micro-bypass stent (Glaukos Corporation), Tra-
`bectome (NeoMedix Corporation),1 Cypass Micro-stent
`(Novartis), and the Xen Gel Stent (Allergan). Investiga-
`tional devices include the Hydrus Micro-stent (Ivantis), and
`MicroShunt implant (InnFocus).2 Other novel trabecular
`bypass procedures include ab interno trabeculotomy using a
`
`Received for publication July 13, 2018; accepted September 22, 2018.
`From the *Faculty of Medicine and Dentistry, University of Alberta
`Medical School, University of Alberta, Edmonton; §Division of
`Ophthalmology, Cumming School of Medicine, University of Cal-
`gary, Calgary, AB; ‡Department of Ophthalmology & Visual Sci-
`ences, Faculty of Medicine, University of British Columbia, Van-
`couver, BC; †Faculty of Medicine, University of Ottawa Medical
`School, University of Ottawa, Ottawa; and ∥Department of Oph-
`thalmology & Visual Sciences, University of Toronto, Toronto, ON,
`Canada.
`Disclosure: P.G. is a Consultant for Alcon, Allergan, Glaukos. The
`remaining authors declare no conflict of interest.
`Reprints: Patrick Gooi, MD, FRCSC, Suite 315—5340 1st Street SW,
`Calgary, AB, Canada T2H0C8 (e-mail: patrick.gooi@gmail.com).
`Supplemental Digital Content is available for this article. Direct URL
`citations appear in the printed text and are provided in the HTML
`and PDF versions of this article on the journal’s website, www.
`glaucomajournal.com.
`Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
`DOI: 10.1097/IJG.0000000000001131
`
`Kahook Dual Blade, a catheter, or a 5-0 polypropylene
`suture. Most of these techniques fall under the category of
`ab interno angle surgery and are bimanual ab interno
`procedures—one hand holds the gonio prism lens (such as a
`Swan Jacobs lens) while the other holds the device or
`inserter suspended in the anterior chamber. Compared with
`traditional incisional glaucoma surgery, MIGS techniques
`hope to offer a safe risk profile while maintaining acceptable
`efficacy.3,4 However, the difference in approach from tra-
`ditional filtering surgery combined with the large variety of
`emerging techniques makes surgical training and education
`difficult.5 Furthermore, the steep learning curve may lead to
`an increased risk of complication during the initial use of the
`device in patients. A realistic angle surgery training model is
`needed to facilitate education of current surgeons and
`glaucoma specialists in these new techniques, and to train
`our surgeons of the future. Current categories of training
`models include virtual-reality, cadaveric, animal, and inan-
`imate with an abundance of literature on virtual-reality
`training models.5
`Ab interno trabecular bypass MIGS involves a differ-
`ent skill set compared with traditional glaucoma surgery in
`that intraoperative gonioscopy is required. A fair degree of
`bimanual coordination is necessary and visualization is key.
`If the lens is held at a suboptimal angle in relation to the
`microscope the view will be inadequate, and excess pressure
`by the gonio prism lens creates corneal striae which can
`further impede the view. Angle surgery also requires much
`higher magnification compared with phacoemulsification
`and excellent depth perception. Proper identification of
`Schlemm canal and the delicate nature of the tissue provides
`additional challenges. Because of the characteristics of the
`tissue within the iridocorneal angle region, most of the
`MIGS techniques have minimal tactile feedback especially
`upon engaging the trabecular meshwork. Instead, the sur-
`gical procedures must be almost entirely guided by visual
`feedback.
`The ideal angle surgery model would use have realistic
`tissue characteristics, employ bimanual technique, be effi-
`cient to set up, and applicable to a multitude of MIGS
`procedures. Some wetlabs for training in iStents have used
`donor corneal rims which are inverted to expose Schlemm
`canal for iStent insertion. The model is relatively simple to
`prepare and utilizes human cadaveric tissue,
`teaching
`trainees the variety in appearance of angles structures and
`tactile characteristics of Schlemm canal. However,
`this
`model lacks bimanual training aspect as a gonio lens is not
`required. Furthermore, as the rim is inverted, Schlemm
`canal
`is presented in a convex configuration which is
`opposite to the positioning from the surgeon’s point of view
`in the operating room.
`The challenge with using human cadaver eyes is that
`corneal edema sets in soon after harvesting, impeding the
`
`J Glaucoma  Volume 28, Number 2, February 2019
`146 | www.glaucomajournal.com
`Copyright r 2018 Wolters Kluwer Health, Inc. All rights reserved.
`
`Petitioner - New World Medical
`Ex. 1034, p. 1 of 4
`New World Medical, Inc. v. MicroSurgical Tech., Inc., IPR2020-01573
`
`

`

`J Glaucoma  Volume 28, Number 2, February 2019
`
`K-RIM (Corneal Rim) Angle Surgery Training Model
`
`view during gonioscopy. Hypertonic gels can be injected
`into the anterior chamber to improve clarity, though this is
`not always successful. Porcine eyes can be used with excel-
`lent corneal clarity yet lack a single continuous Schlemm
`canal instead having segmental canal-like structures termed
`the angular aqueous plexus.6–8 The porcine trabecular
`meshwork is thicker compared with human eyes yielding
`in tactile feedback in vivo.8 Nonetheless,
`differences
`impressive models including porcine eyes with quantitative
`canalography, bovine, and sheep eyes training models have
`been developed due to ease of access and similarity of
`human eyes as substitutes.9–12
`We describe a novel bimanual angle surgery training
`model using human cadaveric corneoscleral rims that provides
`excellent visualization of angle structures, and tactile feedback/
`bimanual approach similar to the real-life experience. The
`model is relatively simple to set up and the required materials
`are accessible to any surgeon with access to an eye bank.
`
`than medical lubricant. A gonio lens (disposable or non-
`disposable) is then held with the bottom immersed in med-
`ical lubricant with one hand, and then the other hand is free
`to implant the trabecular bypass device (iStent or Hydrus)
`or manipulate the trabecular meshwork (perform a trabe-
`culotomy using a Kahook Dual Blade or a gonioscopy
`assisted transluminal trabeculotomy). Video supplementa-
`tion showing preparation of the training model as well
`as iStent
`insertion can be found in the Supplemental
`Digital Content (http://links.lww.com/IJG/A223). The opti-
`cal media between the surgeon and the angle only includes
`medical lubricant and gonio lens. After surgery has been
`performed in one quadrant the rim can be rotated 90 degrees
`in situ, which allows for 4 separate training sessions are one
`rim. The surgical simulation was compared with perform
`MIGS using an artificial eye SimulEYE KDB model
`(SimulEye, California). The surgeons’ feedback was qual-
`itatively assessed with a questionnaire.
`
`METHODS
`Corneoscleral rims from human cadaveric eyes not
`suitable for transplantation or already used for corneal pro-
`cedures such as DSEK are acquired from the eye bank and set
`up as follows (and illustrated in Fig. 1): The rims are trephi-
`nated with a 9 mm diameter trephine centered on the corneal
`rim. A Styrofoam base is placed on a 30-degree angled surface
`using a binder. The rim is placed on the base and the borders
`are secured with pins placed adjacent to the rim but not
`penetrating the rim. To provide realistic training, we ensure
`that Schlemm canal is not buckled during this process. Pins
`are arranged in a semicircular concave pattern open to the
`surgeon, allowing access for surgical instruments. The pins
`generate a concave semicircular perimeter in the Styrofoam
`that seals the tissue against the Styrofoam floor to contain the
`medical lubricant (Fig. 2).
`Medical lubricant (Muko gel) is used to fill the inside of
`the anterior chamber and the area contained within the
`semicircular barrier. Ophthalmic Viscosurgical Devices
`(OVDs) are also an option though usually more expensive
`
`RESULTS
`We have successively completed various angle surgeries
`with the presented training model and find the surgical conditions
`to simulate real life. These angle surgeries include Trabecular
`Microbypass (iStent, Glaukos, California), and needle and dual-
`blade goniotomy (Kahook Dual Blade, New World Medical,
`California), and segmental gonioscopy-assisted transluminal tra-
`beculotomy. The angled positioning of the rim and use of
`medical lubricant provides an excellent viewing field. The model
`uses bimanual approach for effective and realistic utilization of
`the gonio prism lens alongside surgical devices. Tissue used in the
`model is ideal because it recreates the subtle tactile feedback that
`nonhuman models fail to provide and requires gonio prism lens
`visualization, mimicking in vivo conditions. Furthermore, the
`corneoscleral rim provides the realistic curvature of Schlemm
`canal. The ability to rotate the corneoscleral rim also allows for 4
`separate training sessions for increased training efficiency. The
`model is prepared with relative ease and low cost.
`MIGS angle surgery was also successfully performed
`with the artificial eye (SimulEYE KDB, California).
`
`FIGURE 1. K-RIM model with iStent insertion. A, Two pins are placed opposing each other on the scleral portion of the cadaveric tissue
`with enough space to allow insertion of surgical tools and goniolens. B, Gonioscopy view using goniolens to visualize the trabecular
`meshwork (brown line) superficial to Schlemm Canal. C, Gonioscopy view with surgeon in progress of inserting iStent into the trabecular
`meshwork. D, Gonioscopy view after insertion of iStent into the trabecular meshwork. Figure 1 can be viewed in color online at www.
`glaucomajournal.com.
`
`www.glaucomajournal.com | 147
`Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
`Copyright r 2018 Wolters Kluwer Health, Inc. All rights reserved.
`
`Petitioner - New World Medical
`Ex. 1034, p. 2 of 4
`New World Medical, Inc. v. MicroSurgical Tech., Inc., IPR2020-01573
`
`

`

`Arora et al
`
`J Glaucoma  Volume 28, Number 2, February 2019
`
`FIGURE 2. Schematic of K-RIM model set-up. Five pins are arranged in a semicircular perimeter along the nasal aspect. Pins are inserted
`perpendicular to the tissue into the perimeter of the corneoscleral rim to ensure tissue is secured to the Styrofoam base.
`
`Qualitative data from the surgeons comparing the K-RIM
`model to the artificial eye is in Table 1.
`
`DISCUSSION
`The technically demanding nature of MIGS and steep
`learning curve requires advancements in the quality of cur-
`rently available angle surgery training models. Accurate
`tissue simulation is critical for developing skills necessary to
`perform these surgeries. The corneoscleral rim provides an
`effective and accurate simulation for angle surgery training.
`The tissue characteristics of the model replicates tactile
`feedback provided under surgical conditions and will pro-
`vide a way for surgeons to gain proficiency in utilizing
`intraoperative gonioscopy. Further benefits to our model
`are ease of preparation and excellent visualization of angle
`anatomy with additional advantage of allowing training via
`bimanual technique. Low-cost rims may be used multiple
`times providing an efficient cost-effective model for prac-
`ticing angle surgery in high volume with excellent clarity
`allowing exercise of various angle surgeries.
`One group has previously described an angle surgery
`model
`for trabectome that
`involves trephinating whole
`cadaver eyes and gluing on rigid gas permeable (RGP)
`contact lenses.13 The approach merits the bimanual techni-
`que requiring a gonio lens and a clear optical interface to
`visualize angle structures, and similarly uses cadaver eyes
`
`which offer the most realistic tactile feedback.14 The dis-
`advantages are time required to glue RGP lens on the globe
`and securing a supply of RGP lenses.
`that have been
`Other MIGS simulation models
`reported in literature include virtual reality, inanimate, and
`animals. Interestingly, virtual reality models are among
`the most extensively studied albeit the lack of tactile feed-
`back and questionable validity of nonphysical conditions.
`A proposed method of evaluation had assessed 118 eligible
`studies for validity of training models.5 Interestingly, none
`of the trials fit their model of validity; a thought echoed in
`other studies.5,10,14 Attempts have been made to enhance
`current training models including the recent porcine eye
`quantitative canalography and EyeSi models.9,15 Develop-
`ing a standardized quantifiable evidence-based medicine
`validity assessment tool for training models is highly favored
`and an innovative avenue of further investigation. Multiple
`noncadaveric model variations stress tactile feedback sim-
`ilarities, angle visualization, and resource availability as
`potential advantages, but only human eye preparations can
`truly mimic in vivo conditions with high accuracy.
`There are limitations with our model. Because of the
`open sky technique with the OVD lens, one does not expe-
`rience corneal striae, which happens in vivo from excessive
`pressure from the gonioprism. It is important to mentally
`remind trainees to use as little pressure on the gonioprism
`as possible when using this model. Furthermore, as all
`
`TABLE 1. Qualitative Survey Response by Surgeons Comparing K-RIM and SimulEYE KDB Training Models
`K-RIM
`
`Ease of preparation
`Angle visualization
`Bimanual ergonomics
`Surgical ergonomics
`Tissue feedback
`Cost
`
`Good
`Excellent
`Good
`Fair
`Excellent
`Potentially very cost effective if tissue is readily available
`
`SimulEYE KDB
`
`Excellent
`Good
`Excellent
`Excellent
`Good
`Moderate cost
`
`Measures include ease of preparation, angle visualization, bimanual ergonomics, surgical ergonomics, tissue feedback, and cost.
`
`148 | www.glaucomajournal.com
`Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
`Copyright r 2018 Wolters Kluwer Health, Inc. All rights reserved.
`
`Petitioner - New World Medical
`Ex. 1034, p. 3 of 4
`New World Medical, Inc. v. MicroSurgical Tech., Inc., IPR2020-01573
`
`

`

`J Glaucoma  Volume 28, Number 2, February 2019
`
`K-RIM (Corneal Rim) Angle Surgery Training Model
`
`instruments access the angle via the open-sky and not
`through true incision, our model does not replicate aspects
`of surgical egonomics such as oar-locking the instruments in
`the wounds or the management of wound burping issues. In
`comparison, the artificial eye evaluated has a closed system
`with a cornea that produces striae with excessive gonioprism
`pressure and is thus more useful as a training aid for
`intraoperative gonioscopy. Furthermore, the trainee makes
`incisions in the artificial eye model that better replicate the
`subtleties of surgical ergonomics such as instrument oar-
`locking.
`The emergence of a large variety of developing MIGS
`techniques and investigational devices has created the
`challenge of providing surgeons with realistic training
`models. The novel bimanual angle surgery training model
`presented here uses human cadaveric corneoscleral rims
`providing excellent visualization of angle structures and
`realistic surgical conditions. Despite a growing need for
`adequate angle surgery training models, there are few cur-
`rently available which are sufficient for training in MIGS
`techniques. There is a need for a standardized quantifiable
`evidence-based medicine validity assessment tool for train-
`ing models, and this will be an important area of future
`research.
`
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`www.glaucomajournal.com | 149
`Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
`Copyright r 2018 Wolters Kluwer Health, Inc. All rights reserved.
`
`Petitioner - New World Medical
`Ex. 1034, p. 4 of 4
`New World Medical, Inc. v. MicroSurgical Tech., Inc., IPR2020-01573
`
`