Goat's eye integrated with a human cataractous lens: A training model for phacoemulsification

In Vitro and Ex Vivo Models for Assessing Drug Permeation across the Cornea

Drug permeation across the cornea remains a major challenge due to its unique and complex anatomy and physiology. Static barriers such as the different layers of the cornea, as well as dynamic aspects such as the constant renewal of the tear film and the presence of the mucin layer together with efflux pumps, all present unique challenges for effective ophthalmic drug delivery. To overcome some of the current ophthalmic drug limitations, the identification and testing of novel drug formulations such as liposomes, nanoemulsions, and nanoparticles began to be considered and widely explored. In the early stages of corneal drug development reliable in vitro and ex vivo alternatives, are required, to be in line with the principles of the 3Rs (Replacement, Reduction, and Refinement), with such methods being in addition faster and more ethical alternatives to in vivo studies. The ocular field remains limited to a handful of predictive models for ophthalmic drug permeation. In vitro cell culture models are increasingly used when it comes to transcorneal permeation studies. Ex vivo models using excised animal tissue such as porcine eyes are the model of choice to study corneal permeation and promising advancements have been reported over the years. Interspecies characteristics must be considered in detail when using such models. This review updates the current knowledge about in vitro and ex vivo corneal permeability models and evaluates their advantages and limitations.

Bentonite-in hypromellose-poloxamer sol-gel for corneal application of trimetazidine: Study of rheology and ocular anti inflammatory potential

Bentonite is reported to be used for extending ocular drug delivery safely in a controlled manner. Bentonite combined hydroxypropyl methylcellulose (HPMC)-poloxamer based sol-to-gel formulation has been developed for the prophylactic ocular anti-inflammatory effect of trimetazidine after corneal application. HPMC-poloxamer sol formulation was prepared incorporating trimetazidine to bentonite at 1: 2*10^-5 to 1:5*10^-6 ratios using cold method, and investigations were carried out in carrageenan-induced rabbit eye model. Pseudoplastic shear thinning behavior without any yield value and high viscosity at low shear rate were the positive attribute of the tolerability of the sol formulation after ocular instillation. Presence of bentonite nanoplatelets revealed more sustained in vitro release (~79-97 %) and corneal permeation (~79-83 %) over a period of 6 h in comparison to its absence. Prominent acute inflammation has been produced in the carrageenan-induced untreated eye, whereas the absence of ocular inflammation has been noticed in the previously sol-treated eye even after carrageenan injection. HPMC-poloxamer-based formulation exhibited stronger binding affinity (5.13 kcal/mol) in the presence of bentonite rather than its absence (3.99 kcal/mol), resulting in a stable and sustained effect. HPMC-poloxamer in-situ gel of trimetazidine containing bentonite could be utilized for sustained ocular delivery and the control of ophthalmic inflammation prophylactically.

Formalin-assisted training eyes for ophthalmic wet lab practice

The foundation of an ophthalmologists’ microsurgical career begins in the wet lab. Training on donor cadaveric, animal like goat or pig eyes provide the most realistic surgical environment, however, the availability of a donor’s eyes for practice is limited. This scarcity is further escalated in this current coronavirus disease 2019 pandemic where eye donations have decreased. Even among those eyes which find their way into the wet lab, quite a few would have collapsed significantly making training difficult. Therefore, we looked at ways to salvage these collapsed globes. We describe a novel way of salvaging the collapsed eyeballs by injecting formalin in slow boluses into the vitreous cavity. The longer maintenance of the globe integrity without necessitating repeated injections facilitates better quality of surgical training and optimal utilization of these eyes.

Reworking protocols of ophthalmic resident surgical training in the COVID-19 era - Experiences of a tertiary care institute in northern India

Purpose:

Coronavirus Disease 2019 (COVID-19) pandemic has negatively impacted medical professionals in all fields of medicine and surgery in their academic, clinical and surgical training. The impact of surgical training has been described as ‘severe’ by most ophthalmology residents worldwide due to their duties in COVID-19 wards, disruption of outpatient and camp services.

Methods:

Ophthalmic surgery demands utmost accuracy and meticulousness. Fine motor proficiencies, stereoscopic skills and hand–eye coordination required can only be achieved by practice. So, a multileveled structured wet-lab teaching schedule was prepared for the residents and implemented to bridge this gap between theory and practice at our tertiary care institute. A semester-wise training schedule was made with the proper distribution of wet-lab and simulator training. Surgeries like phacoemulsification, scleral buckling, pars plana lensectomy and vitrectomy, trabeculectomy and intravitreal injections were practised by the residents on the goat eyes. Simulator training was provided for phacoemulsification and vitrectomy to increase the hand–eye coordination of the residents.

Results:

Residents noticed improvement in their surgical skills and ambidexterity post wet-lab and simulator training . It also increased their confidence and provided essential surgical skills required to be used in the operation theater later.

Conclusion:

It is imperative that wet-lab training be included in the residency training programme in this COVID-19 era.

Animal and cadaver human eyes for residents' surgical training in ophthalmology

In ophthalmology residency programs surgical training plays a vital role in creating confident and skillful surgeons. As almost all ophthalmic surgery needs microscope training, creating a well-taught environment for hand-eye coordination, ocular tissue handling, and anticipation of complications is essential. Wet lab training with animal or cadaver human eyes offers diverse possibilities. We conducted a thorough literature search on various databases to identify the existing literature on wet labs. The results revealed constructive efforts for training novice surgeons in all surgical ophthalmology subspecialties. Wet lab models were initially used only to practice cataract surgery; however, now various complex ocular procedures can be practiced. Ocular surface, corneal, iris, lenticular, scleral, vitreoretinal, extraocular, eyelid, and other adnexal surgeries were reproduced and mastered in many ways. Importantly, with repeated surgical practice, residents gained an increasing level of confidence with enhanced surgical accuracy. In addition, we propose a few novel techniques of various other procedures.

Essentials of setting up a wet lab for ophthalmic surgical training in COVID-19 pandemic

Wet labs are an extremely important training tool, especially in times of a global COVID-19 pandemic, where surgical training can be minimal. They help the trainee learn and practice in a risk-free environment, without an imminent of a complication or failure, also allowing them the chance to execute the steps of a surgery repeatedly. We summarize all the key ingredients required from setting up a wet lab to improve the surgical skill of the trainees. The review also discusses various eyeball fixating devices, preparation of the eye for various types of ocular surgeries, and the role of simulation-based training in today's scenario.

Oculoplastic surgical simulation using goat sockets

Purpose: To describe a reproducible and easily available goat socket model for training of various oculoplastic operations, and to evaluate trainees' perception of this training model in terms of their learning progress and satisfaction.Methods: Goat sockets including orbital rim and eye with eyelids were harvested in form of a split-head model. Ophthalmology residents underwent individual surgical training using the goat socket model, supervised by an oculoplastic attending. Participants completed a questionnaire in form of a 5-point Likert Scale to evaluate their learning progress and satisfaction.Outcome Measures: Types of oculoplastic operations performed using the goat socket models, and participants' rating of their learning progress and satisfaction were reported.Results: A wide range of oculoplastic operations including both eyelid and orbital operations could be simulated because of similarities of the goat eye model to the human eye anatomy. Fifteen ophthalmic trainees participated in surgical training using the goat eye model. All (100%) participants agreed that surgical simulation using the goat socket model increased their skills in surgical instrumentation and carrying out surgical steps, and their confidence in operating on patients. Most (87%) agreed the model resembled reasonably well compared to surgeries in human, and 93% would recommend training with the model to fellow resident ophthalmologists before operating on human patients.Conclusions: Oculoplastic surgical training using goat sockets is simple, readily available, and inexpensive. Trainee users showed promising feedback and positive learning progress using the goat socket model.

Quantitative shadowgraphy of aerosol and droplet creation during oscillatory motion of the microkeratome amid COVID-19 and other infectious diseases

High-speed shadowgraphy showed droplets generated during flap cut with microkeratome. However, aerosolization of these droplets was unlikely because these droplets would settle on surface before aerosolization.

Purpose:

To quantify the atomization of liquid over the cornea during flap creation using microkeratome using high-speed shadowgraphy.

Setting:

Laboratory investigational study.

Design:

Laboratory study.

Method:

In an experimental setup, flap creation was performed on enucleated goat's eyes (n = 8) mounted on a stand using One Use-Plus SBK Moria microkeratome (Moria SA) to assess the spread of aerosols and droplets using high-speed shadowgraphy. Two conditions were computed. A constant airflow assumed uniform air velocity throughout the room. A decaying jet assumed that local air velocity at the site of measurements was smaller than the exit velocity from the air duct.

Results:

With the advancement of the microkeratome across the wet corneal surface, the atomization of a balanced salt solution was recorded on shadowgraphy. The minimum droplet size was ∼90 μm. The maximum distance traversed was ∼1.8 m and ∼1.3 m assuming a constant airflow (setting of refractive surgery theater) and decaying jet condition (setting of an operating theater with air-handling unit), respectively.

Conclusions:

The microkeratome-assisted LASIK flap creation does seem to cause spread of droplets. The droplet diameters and velocities did not permit the formation of aerosols. Therefore, the risk of transmission of the virus to the surgeon and surgical personnel due to the microkeratome procedure seems to be low.

A systematic review of simulation-based training tools for technical and non-technical skills in ophthalmology

To evaluate all simulation models for ophthalmology technical and non-technical skills training and the strength of evidence to support their validity and effectiveness. A systematic search was performed using PubMed and Embase for studies published from inception to 01/07/2019. Studies were analysed according to the training modality: virtual reality; wet-lab; dry-lab models; e-learning. The educational impact of studies was evaluated using Messick's validity framework and McGaghie's model of translational outcomes for evaluating effectiveness. One hundred and thirty-one studies were included in this review, with 93 different simulators described. Fifty-three studies were based on virtual reality tools; 47 on wet-lab models; 26 on dry-lab models; 5 on e-learning. Only two studies provided evidence for all five sources of validity assessment. Models with the strongest validity evidence were the Eyesi Surgical, Eyesi Direct Ophthalmoscope and Eye Surgical Skills Assessment Test. Effectiveness ratings for simulator models were mostly limited to level 2 (contained effects) with the exception of the Sophocle vitreoretinal surgery simulator, which was shown at level 3 (downstream effects), and the Eyesi at level 5 (target effects) for cataract surgery. A wide range of models have been described but only the Eyesi has undergone comprehensive investigation. The main weakness is in the poor quality of study design, with a predominance of descriptive reports showing limited validity evidence and few studies investigating the effects of simulation training on patient outcomes. More robust research is needed to enable effective implementation of simulation tools into current training curriculums.

Optimal refinement of residents' surgical skills by training on induced goat's eye corneoscleral perforation

Surgical skill enhancement for the residents under training can be performed through various efforts. Here in this report, the authors describe a technique of corneoscleral perforation repair on goat's eye, as the tissue resemblance and the reality of experience while performing crucial steps are similar to human eyes. Beginning from tissue handling, optimal suture placement was taught with an intention to impart quality techniques of traumatic globe injury repair. Therefore, rather than training on expensive artificial eye model, training budding surgeons on goat's eye gives much more realistic tissue handling experiences in the presence of constant challenges almost similar to human eyes.