Discussion

The efficacy of preclinical surgical exposure and simulation for ophthalmology trainees has been widely investigated,3 and of this, wet lab training plays a central role. Although there are increasingly more options for computerised simulations to teach surgical techniques for cataract and vitreoretinal procedures,4 instruction on cadaveric tissues remains a mainstay for teaching various corneal, strabismus and complex anterior segment procedures, as well as the tenets of globe rupture repair. Moreover, given the expense of virtual simulation and the wide availability of various cadaveric tissues (human or animal) by comparison, this modality often represents the sole form of preclinical surgical training in many low-resource settings.

Consequently, there is an obvious need for conditions in the surgical wet lab that closely mimic those in the OR, allowing trainees to cultivate good practices that will translate to clinical practice, speeding skill acquisition and minimising complication rate in the process. Chief among these is the device used to fixate the practice material. Stability, affordability and accurate simulation of facial contours are crucial elements of an effective eye mount in the ophthalmology wet lab, but there currently exists no widely distributed system that incorporates all three of these key characteristics.

Here, we designed and constructed a low-cost, high-fidelity eye mount for surgical training that is open source for wide distribution and usage. TEMPO provided capable of stable, reliable fixation of cadaveric eyes throughout surgical practice sessions—something that the authors have not experienced with other systems, which routinely require ongoing adjustment and refixation over the session. Its suction-based design enables easy achievement and modulation of physiologic/supraphysiologic IOP levels, as desired, by adjustment of the attached syringe. This avoids the pitfalls of non-suction methods, such as the pins/elastics commonly employed with foam mannequin (trial) heads, which frustrate the trainee with frequent loss of globe turgidity and attendant chamber collapse with surgical penetration of the eye. Further, the flat base and reassuring mass of TEMPO provide a solid platform to suture against, unlike the foam heads, which are light and have the tendency to roll, providing very little stability to the learning surgeon.

Integral to the optimal function of a surgical mount is the mimicry of the contours of a patient’s face. Practice without such leads to a tendency for trainees to be comfortable with actions under ‘ideal’ circumstances, but unprepared to perform the same motions over/around facial structures in the OR. This is a major limitation of the flat Mastel-Mandell eye mount. It provides good suction to keep cadaveric eyes in position for surgical manipulation, but lacks the facial contours required for trainees to learn how to effectively place their hands when learning to suture on a real patient, and certainly cannot emulate the various anatomical challenges such as a deep brow or a long nose that frequently confront ophthalmic surgeons. Despite its other drawbacks, the simple foam head has strength in this area, with anatomically correct facial contours. The low-cost Spring action Apparatus for Fixation of Eyeball device designed by Ramakrishnan et al2 is a similar suction design, but one for which the authors developed a ‘mask’ housing that can be superimposed on the mount to approximate facial contours. However, it is obvious from their photographs that this is a non-anatomical design, and there appears to be no solid mechanism of fixation between the shroud and the mount. Indeed, the authors comment that their preference is for handheld usage of the shroudless mount, attesting to these very limitations. TEMPO provides facial anatomy that is not only realistic and accurate, but also modifiable.

Although the Ramakrishnan et al’s design looks promising in many respects, it lacks in availability: it does not appear to be commercially produced, and there are no blueprints available off which one could reproduce their design. Consequently, we were unable to obtain a copy of their device for testing and comparison to TEMPO. Comparatively, our mount can be reproduced and customised by anyone with access to a computer and small 3D printer. Their steel ‘mask’, by contrast, looks to be a single-design piece, and making any alterations to its contours would require a ground-up redesign each time. It should also be added that different ethnicities and age groups have various head sizes and diverse facial contours, and these features can be easily incorporated into TEMPO by adjusting the digital 3D design. For instance, a particularly shallow or deep orbit (common surgical situations) is readily achieved.

Cleanliness and sanitation are a major consideration in the surgical wet lab, given that the cadaveric materials employed are inherently biohazardous in nature, and this is another department in which the existing mount options fall short. The Mastel-Mandell incorporates no means whereby to detach the suction system for effective disinfection/replacement, which can potentially lead to accumulation of cadaveric material within the tubing itself. The authors have experienced that foam heads quickly accumulate cadaveric residue, and have no mechanism for cleaning, effectively making them single-use-disposable. By contrast, TEMPO is conceived to be modular, readily cleaned (as an all-polymer design), and extensively reusable—parts can even be printed as subunits if one were to break/require replacement. Also, unlike the other suction mounts, ours is readily adapted to accommodate non-cadaveric eyes, which increases flexibility and eliminates the issue of biohazard waste altogether. A summary of the characteristics of TEMPO compared with existing mount systems is presented in table 1.

Although we feel the TEMPO mount largely addresses the shortcomings of present mount systems, this project still presented unique technical challenges. 3D printing is becoming increasingly ubiquitous, but it should not be overlooked that our design relies on the availability of such facilities and the attendant technical expertise, which may limit its utility in extremely resource-constrained settings. Prototyping TEMPO involved numerous design revisions and multiple prints to refine; although the mount, as provided, is turnkey ready-to-print, we realistically expect that centres looking to customise our design will have to undergo a similar process.

There are also other limits that we intend to improve over subsequent phases. As the eye is attached to a fixed base with vacuum created by the syringe, it cannot replicate the passive extraocular movements experienced during surgery. We plan to update the design with a ball and socket mount that can simulate this movement in future iterations and release this update online. Although we selected PLA based on its availability as one of the most common 3-D printing filaments as well as its biodegradable nature, it is somewhat porous, limiting the duration for which a suitable vacuum can be maintained. In addition, theoretically minute amounts of biowaste could potentially still permeate the pores of the PLA material, though our mount shows no signs of discolouration or contamination after multiple uses. We plan to continue work on improving and testing different fixation designs, such as a compressive belt surrounding the eye as well as different filament materials in the future, releasing each of these online to allow for ongoing refinement of the design.

As part of this publication, we are releasing TEMPO as a free and open-source file (https://www.ophthalmologyexplorer.com/innovations/project-one-7f9kx). The accessible nature of the file allows anyone in the world to download and 3D print the product for testing. They can also alter the downloaded computer-aided design file to fit their needs or make adjustments to existing components. As 3D printing becomes more ubiquitous, we hope wet lab training equipment can be customised to fit resource-limited training settings. Therefore, not only will TEMPO refine some of the challenges of previous eye mounts, but also maximise affordability of resources for learning.