A simulator for Goldmann Applanation Tonometry: a novel approach to training

doi:10.21203/rs.3.rs-2503331/v1

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A simulator for Goldmann Applanation Tonometry: a novel approach to training

https://doi.org/10.21203/rs.3.rs-2503331/v1

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BACKGROUND: Goldmann Applanation Tonometry (GAT) is the gold standard technique for measuring intraocular pressure (IOP) and an essential skill required early in clinical ophthalmic practice. Medical students, residents, and ophthalmic technicians often practice on real-life patients or courageous volunteers, increasing the chance of possible cross infections, corneal abrasions, and incorrect IOP measurements. The Goldmann Applanation Tonometry Simulator (GatSim) is a novel online application aimed to act as an adjunct to standard GAT training.

METHODS: A website was created using HTML and JavaScript ES6, tested on Google Chrome version 104, and hosted on GitHub. The user interface was designed to provide experiential learning via opportunities to practice the technical components of GAT including tonometer and mires positioning, real-time feedback, and new patient selection. The simulation was tested by our research team to ensure that it appropriately mimicked GAT in the user interface.

RESULTS: We developed a web application which simulates GAT. The latest version can be found at gatsim.com. Beginner operators can now gain initial experience on our model before seeing patients, a safety measure which may mitigate potential adverse events and improve overall outcomes.

CONCLUSIONS: GatSim is the world’s first online Goldmann Applanation Tonometry simulator. Its utility is impactful, allowing students to learn the mechanics of GAT via an easy-to-use online application while also demonstrating the power of simulation in education. We hope such technology can help develop GAT trainee skill sets, minimize potential complications in the performance of GAT, and provide inspiration for future developments of online simulators.

Intraocular pressure

glaucoma

Goldmann applanation tonometry

tonometer

simulator

ophthalmology

software

JavaScript

simulation

medical education

Tonometry is a procedure to measure the pressure of fluid inside the ocular globe, termed intraocular pressure (IOP). The calculation of this measurement is based on the Imbert-Fick Principle, which can be expressed as

.(1-3) Deviations in IOP can indicate pathologies, including glaucoma, choroidal detachment, and uveitis.(4) Thus, measuring IOP is an essential component for monitoring eye health.(4) In the 1950s, scientist Hans Goldmann developed Goldmann Applanation Tonometry (GAT), the present-day gold standard technique for the measurement of IOP.(5) In addition to GAT, several tools have been developed to measure IOP, such as the Tonopen, ocular blood flow tonograph (OBF), non-contact tonometer (NCT), and transpalpebral tonometer (TCT). While some of these techniques have unique advantages, GAT remains the most accurate IOP measurement technique across ophthalmology practices and demonstrates superior interobserver reliability.(6) One disadvantage of GAT is the high level of skill required for operation.(7) Automated devices such as the Ocular Response Analyzer (ORA), often used by ophthalmic technicians or nurses for measuring IOP during virtual visits, have shown more effortless operability.(8) Unskilled operators can cause harm to patients through the performance of GAT by potentially causing a corneal abrasion, increasing the risk for cross-infection, or reporting incorrect IOP measurements.(9) In response to GAT, these other modalities have been developed, but none have surpassed its precision.(6) Given the user skill requirement, appropriate training is essential. Present-day training involves a courageous volunteer or patient and can involve risk. Physical models of artificial globes for GAT training have been described; however, they require materials that may be inaccessible and costly, and they do not replicate the human anatomy exactly.(9-10) To advance training in the current age, we developed GatSim, an online application which mimics the steps of GAT through an online interface. We believe the GatSim application will provide an initial training opportunity to new students of GAT and ultimately result in a more efficient, safer, and enjoyable learning experience for all parties involved, including students, teachers, and patients.

Sketches of the proposed user interface were iteratively designed using presentation slides software. Then, a web app was created that implemented the proposed design. The design of an online webapp was chosen as it is easily accessible. The webapp used HTML5, CSS, and JavaScript ES6 and was iteratively tested on multiple web browsers including Google Chrome version 104. Throughout the process, code was tracked and saved in a repository in GitHub (Microsoft Corporation, Redmond, WA, USA). The “GitHub pages” on GitHub was used to host the website at the domain https://gatsim.com.

Description of user interface

GatSim version 004 displays four graphical user interfaces (GUI). A high-definition image of a model patient in the bottom left panel (Figure 1C), a corresponding zoomed-in image on the top left panel (Figure 1A), a display of mires in the top right panel (Figure 1B), and a control console in the bottom right panel (Figure 1D). The computer mouse or keyboard controls (up, down, left, and right arrows) can be used to move the digital tonometer (bottom left panel) in the X and Y planes, simulating the mechanics of a tonometer attached to a slit lamp in real life. Right and left mouse click buttons or the keyboard controls “w” and “s” are used to zoom in and out, representing movement in the Z plane. Initially, the mires will appear faint. As the user zoom’s in further, the mires become more transparent and eventually turn blue colored to represent the “ghost” mires observed once the tonometer tip is near the cornea. At the appropriate zoom level, green mires lines appear. The controls “spacebar” and “shift” simulate the force adjustment knob by increasing and decreasing the applanating force. Similar to reality, in the simulator, the positioning of the mouse on the pupil provides the appropriate symmetrical visualization of the mires lines.

The simulation also reveals mistakes. For example, once on the cornea, with the green mires visible, any additional movement displays the text “corneal abrasion! Don’t move while on the cornea” under the console in the bottom right GUI. To avoid this warning, the user should zoom out with the mouse and move accordingly before zooming back onto the cornea. Upon correct alignment of the mires, the text “Mires aligned!” displays under the console (See Additional file 1). Table 1 provides a summary of features found in GatSim.

Table 1. Summary of features

	Finding or Recommendation	Reference
1.	Mouse or keyboard-directed movement of the simulated tonometer The simulator models slit lamp movement in all 3 directional planes (x, y, and z). The user can control movement in the panel seen in Figure 1C. A magnified view of the image in Figure 1C is displayed in Figure 1A. - Horizontal movement (x-axis) controls: move the mouse left or right or press the left and right arrow keys on the keyboard - Vertical movement (y-axis) controls: move the mouse up or down or press the up and down arrow keys on the keyboard - Zoom in or out (z-axis controls): right or left click hold on the mouse or “w” and “s” on the keyboard, respectively	Figure 1A, C Supplemental File 1
2.	Display of tonometer aperture view and mires lines The simulator models the circular view of the tonometer aperture and mires lines. As the user zooms in on the patient panel (Figure 1C), blue “ghost” mires followed by green mires appear.	Figures 1A, B, C
3.	Movement of mires When zoomed appropriately with the mires visualized, the mires lines move with realistic dimensionality as the user moves the simulated tonometer tip. The force adjustment knob is simulated by holding the keys “spacebar or “shift” to increase or decrease pressure reading, respectively.	Figure 1B, C
4.	Text display console, control panel, and photo selection Console: At a specific zoom level (when green mires are present), movement of the simulated tonometer tip will elicit a text display warning under “Console.” Furthermore, a correct alignment of the mires indicating the accurate IOP^a measurement will display “Mires aligned!” Control panel: the display of keyboard controls for the simulator, coordinates (X, Y, Z) of mouse position, pressure reading, and drop-down photo selection option for a new patient encounter	Figure 1D

Key features of our simulator

^aIOP: Intraocular pressure

Motivation for simulators

Online simulators are a good alternative learning platform because they can be easily accessed, maintained easily and efficiently, and provide a comprehensive and immersive learning experience without the need for expensive equipment.

Simulators have shown efficacy in the training of several ophthalmologic techniques. The Retinoscopy Simulator, Cataract Master, and Strabismus Simulator are examples of popular interactive online simulations for ophthalmology training.(11–13) More sophisticated simulators with external components also exist and have shown utility. For example, the Eyesi surgical virtual reality simulator has demonstrated effectiveness in reducing complication rates in cataract surgery.(14)

GAT is the standard modality for measuring IOP. Elevated IOP levels are a primary risk factor in glaucoma, and management entails monitoring and reducing pressures to prevent irreversible blindness.(15) Studies have shown that GAT IOP measurements are biased toward even numbers due to characteristic even numbered tick marks on the force adjustment knob.(16) An application such as GatSim is an ideal model for implementing gamification, which could deter such biases. For instance, issuing tasks for the user to conduct, such as reporting specific IOP measurements. The gamified simulation could be modeled to have correct values consisting of mainly odd numbers, thus helping to improve future biases such as even-numbered tick mark reporting. The potential for additional applications in gamification also exists.

Furthermore, new trainees may be more likely to cause potential patient risks. This may include corneal abrasions, cross infections, more uncomfortable exams, lack of confidence during the procedure, inability to align the mires lines correctly, and incorrect IOP measurements.

A recent study in England testing optometrists’ ability to measure IOP using GAT demonstrated a 21.9% failure rate on the first attempt. This may indicate a lack of core competencies in this group of optometrists, especially if they are interested in glaucoma care management.(17) The GatSim application allows anyone to practice the basic mechanics of GAT freely online. This can help familiarize practitioners with the overall idea, correct steps, and slit lamp mechanics involved in utilizing GAT. We hope that with practice, users will develop a form of muscle memory to carry out the correct steps and mechanics and thus aid in real-life GAT usage.

A worldwide 2020 survey reported that 265 out of 321 physicians believe that the e-learning experience acquired during the COVID-19 pandemic will be used in the future of ophthalmology training.(18) This further supports the initiative of online simulators as adjunctive training to traditional approaches. GatSim is a novel addition to the free e-learning repository for ophthalmology training.

Future updates and modifications to GatSim should aim to develop a more realistic GAT simulator to train students more effectively. The computer mouse is a fitting device for simulating slit lamp kinematics. The current design allows mouse movement functions in the X and Y planes. The incorporation of Z plane directionality (in place of the current zoom in and out controls “w” or right mouse click, and “s” or mouse left click, respectively) to forward and backward movement of the mouse will improve slit lamp representation. Another feature of slit lamp mechanics includes fine control movement with the joystick. We recommend that this also be implemented in future versions. An additional GUI can be introduced, displaying an animated image of the applanation tonometer and model patient’s face directed at an approximately 5 - 15-degree angle to mimic a practitioner's real-life side viewing experience. The GUI containing the applanation tonometer could then move in real-time, in conjunction with the mouse’s movements.

The greater context

The intended uses of this software include conducting future studies to investigate effectiveness of GatSim as an initial training modality for GAT, providing an open-source project for others to learn from and develop further, advancing the field of simulation-based medical education, and presenting an opportunity for trainees to develop their GAT skills in a free, accessible, and safe manner.

In addition to GatSim and standard training protocols of specific institutions, Moorfield Eye Hospital’s Standard Operating Procedure (SOP) is another valuable source of information. The SOP contains the procedural steps of GAT with corresponding rationale.(10)

Future directions may include continued application updates for enhanced user-control interaction and studies comparing GAT technique skills between GatSim and standard-trained students. A telemedicine-based application is another possible avenue where GatSim’s user interface can be integrated with digital medical equipment for remote delivery of eye care services such as slit lamp examination and GAT.

GatSim is a novel development, and there is currently no existing software or application for comparison. Still, potential limitations exist. While the mouse is an apparatus for mimicking the slit lamp’s kinematics, it may not wholly be able to do so. For instance, the slit lamp’s vertical motion is conducted through the rotation of the joystick. No analogous component can represent the joystick on a standard computer mouse. Theoretically, a joystick could be developed and configured in place of the mouse to offer a complete simulation of slit lamp movement controls.

GatSim is an online application that is free to use at gatsim.com. The simulator mimics the mechanics and functions of GAT on the slit lamp through the computer keyboard and mouse controls. The goal of GatSim is to provide a free-to-use simulation-based training tool for the initial preparation of GAT, an important ophthalmic clinical skill. We hope this application can improve training efficiency and mitigate potential adverse events.

GAT Goldmann applanation tonometry

IOP Intraocular pressure

OBF Ocular blood flow tonograph

NCT Non-contact tonometer

TCT Transpalpebral tonometer

ORA Ocular Response Analyzer

GUI Graphical user interface

SOP Standard Operating Procedure

Ethics approval and consent to participate

No human or other animal data were included in this study.

Consent for publication

Not applicable.

Availability of data and materials

The software developed as part of this manuscript is intended to be open source and is publicly available on GitHub at https://github.com/ryerrabelli/TonometrySimulation. It will be permanently deposited in an online public repository on manuscript publication.

Project name: GatSim: A simulation to teach Goldmann Applanation Tonometry

Project homepage: http://gatsim.com (latest version) or https://ryerrabelli.github.io/TonometrySimulation/src/v004

Operating system(s): Platform independent. Tested on systems including Chrome 104 on macOS 12.4, Safari on macOS 12.4, and Chrome on Windows

Programming language: JavaScript ES6, JQuery, HTML5, CSS

Other requirements: N/A

License: GNU General Public License Version 3 (29 June 2007)

Any restriction to use by non-academics: none

Competing interests

The authors have no competing interests to declare.

Funding

The authors declare that no funds, grants, or other support were received specifically for the preparation of this manuscript.

Authors’ contributions

AH conceived the initial idea and worked on the design of the software. RSY wrote the source code and developed the user interface functionality. ASA provided help in conceiving the idea. AH, RSY, ASA, ADS, and JB contributed to writing and editing the final manuscript. All authors read and approved the final manuscript.

Acknowledgments

Not applicable.

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Ferris JD, Donachie PH, Johnston RL, Barnes B, Olaitan M, Sparrow JM. Royal College of Ophthalmologists’ National Ophthalmology Database study of cataract surgery: report 6. The impact of EyeSi virtual reality training on complications rates of cataract surgery performed by first and second year trainees. Br J Ophthalmol. 2020 Mar 1;104(3):324–9.
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No competing interests reported.

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A simulator for Goldmann Applanation Tonometry: a novel approach to training

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Abstract

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Background And Introduction

Methods And Implementation

Description of user interface

Results And Discussion

Motivation for simulators

The greater context

Conclusion

Abbreviations

Declarations

Ethics approval and consent to participate

Consent for publication

Availability of data and materials

Competing interests

Funding

Authors’ contributions

Acknowledgments

References

Additional Declarations

Supplementary Files

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