A Discrete Event Simulation model to evaluate the treatment pathways of patients with Cataract in the United Kingdom

Background The number of people affected by cataract in the United Kingdom (UK) is growing rapidly due to ageing population. As the only way to treat cataract is through surgery, there is a high demand for this type of surgery and figures indicate that it is the most performed type of surgery in the UK. The National Health Service (NHS), which provides free of charge care in the UK, is under huge financial pressure due to budget austerity in the last decade. As the number of people affected by the disease is expected to grow significantly in coming years, the aim of this study is to evaluate whether the introduction of new processes and medical technologies will enable cataract services to cope with the demand within the NHS funding constraints. Methods We developed a Discrete Event Simulation model representing the cataract services pathways at Leicester Royal Infirmary Hospital. The model was inputted with data from national and local sources as well as from a surgery demand forecasting model developed in the study. The model was verified and validated with the participation of the cataract services clinical and management teams. Results Four scenarios involving increased number of surgeries per half-day surgery theatre slot were simulated. Results indicate that the total number of surgeries per year could be increased by 40% at no extra cost. However, the rate of improvement decreases for increased number of surgeries per half-day surgery theatre slot due to a higher number of cancelled surgeries. Productivity is expected to improve as the total number of doctors and nurses hours will increase by 5 and 12% respectively. However, non-human resources such as pre-surgery rooms and post-surgery recovery chairs are under-utilized across all scenarios. Conclusions Using new processes and medical technologies for cataract surgery is a promising way to deal with the expected higher demand especially as this could be achieved with limited impact on costs. Non-human resources capacity need to be evenly levelled across the surgery pathway to improve their utilisation. The performance of cataract services could be improved by better communication with and proactive management of patients.Peer reviewedFinal Published versio

High Fidelity Haptic Rendering for Deformable Objects Undergoing Topology Changes

International audienceThe relevance of haptic feedback for minimally invasive surgery has been demonstrated at numerous counts. However, the proposed methods often prove inadequate to handle correct contact computation during the complex interactions or topological changes that can be found in surgical interventions. In this paper, we introduce an approach that allows for accurate computation of contact forces even in the presence of topological changes due to the simulation of soft tissue cutting. We illustrate this approach with a simulation of cataract surgery, a typical example of microsurgery

Estimation of the mechanical properties of the eye through the study of its vibrational modes

Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz - 10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye.Comment: Published in PLoS ONE as Open Access Research Article. 17 pages, 5 color figure

Astigmatism and Pseudoaccommodation in Pseudophakic Eyes

noAdvanced IOLs with circumferential zones of different power provide pseudoaccommodation. We investigated the potential for power variation with meridian, namely astigmatism, to provide pseudo-accommodation. With appropriate power and axis orientations, acceptable pseudo-accommodation can be achieved

Application of discrete-event simulation to health services research: analysis of needs and demand for elective

Les tècniques computacionals de simulació han permès la introducció de metodologies de modelització per analitzar sistemes complexes a través d'experimentació virtual, i així avaluar l'impacte d'intervencions sobre els serveis sanitaris. La simulació d'esdeveniments discrets és una tècnica ben coneguda en la investigació operativa que s'ha desenvolupat principalment en l'àmbit de la investigació militar i els sistemes de producció industrial. En l'àmbit mèdic, els models de Markov i els arbres de decisió han estat utilitzats de manera extensa a pesar de les seves limitacions per a reproduir els problemes sanitaris acuradament. La simulació d'esdeveniments discrets està guanyant popularitat degut a la seva flexibilitat per a representar sistemes reals tenint en compte les característiques dels pacients i l'escassedat de recursos present en la provisió de serveis sanitaris. Aquesta tècnica s'ha utilitzat per a analitzar problemes relacionats amb la gestió de recursos sanitaris, però les seves possibilitats per a analitzar problemes més amplis relacionats amb la dinàmica de les poblacions s'han explorat poc. Tradicionalment, les necessitats i la demanda de serveis sanitaris s'han analitzat per separat. En l'aplicació que es presenta es va analitzar la resposta del sistema sanitari tant a la població amb necessitat de cirurgia com als pacients inclosos en llistes d'espera.En aquest sentit, la principal contribució d'aquesta tesi és l'aplicació de la simulació d'esdeveniments discrets a la recerca en serveis sanitaris des d'un punt de vista epidemiològic. A més, el model és complexe a nivell estadístic degut a la diversitat de fonts d'informació i de característiques de les dades que defineixen la informació principal d'entrada; les lleis del sistema modelat van requerir una metodologia ad hoc específica per a recollir i processar aquesta informació per tal de generar les dades d'entrada que necessitava el model de simulació. Per tant, una part important d'aquest treball s'ha dedicat a desenvolupar aquesta metodologia d'anàlisi de les dades d'entrada.Es va construir un model de simulació d'esdeveniments discrets per a analitzar les necessitats i la demanda de cirurgia de cataractes en el sector públic de Catalunya. El model reprodueix el procés de la cirurgia de cataractes, des de la incidència de necessitat de cirurgia, passant per la demanda, la inclusió en una llista d'espera i la cirurgia finalment. Es descriu detalladament la metodologia per a analitzar les dades d'entrada del model. Els paràmetres del model es van estimar utilitzant diferents fonts d'informació, tant bases de dades administratives com de recerca.Es descriu detalladament la implementació del model en el software SIMUL8 i com es pot enllaçar amb Excel per a fer el model més amigable per a usuaris no experts en simulació. Es van realitzar diverses anàlisis de sensibilitat per a avaluar l'impacte de la variabilitat de les estimacions dels paràmetres d'entrada (validació), l'impacte de diferents estratègies de gestió de la llista d'espera segons diferents escenaris de temps mitjà d'espera, i per a avaluar la transferibilitat de la metodologia. Per a avaluar la transferibilitat es va aplicar la metodologia per a calcular els paràmetres d'entrada a diferents àmbits (altres Comunitats Autònomes d'Espanya). Els resultats del model es van utilitzar per a analitzar variacions geogràfiques en l'impacte d'introduir un sistema de priorització de llistes d'espera. A més, es va combinar la informació de les Comunitats Autònomes per a utilitzar el model per a avaluar el volum de necessitat de cirurgia de cataractes a Espanya segons diferents criteris d'indicació de cirurgia. La transferibilitat de la metodologia a d'altres cirurgies electives es va avaluar adaptant el model per a analitzar necessitats i demanda de cirurgia de pròtesi de genoll a Espanya.L'estudi de les necessitats i la demanda de serveis sanitaris és rellevant en la mesura que s'observa un volum important de necessitats no ateses. La diferència entre la necessitat i la provisió de serveis pot ser massa gran per poder-la resoldre, però la utilització de models que avaluïn l'impacte de modificacions en la quantitat de recursos utilitzats o l'impacte de polítiques sanitàries en la gestió de la necessitat i la demanda de serveis és útil en la presa de decisions sanitàries.Computer simulation techniques have allowed the introduction of modeling methodologies that analyze complex systems through virtual experimentation to assess the potential impact of interventions on health services. Discreteevent simulation is a well-known technique in operations research, and has mainly been developed in the context of military research and manufacturing systems. In the medical setting, Markov models and decision trees have been extensively used despite their limitations in reproducing healthcare problems accurately. Discrete-event simulation is gaining popularity because of its flexibility in representing real systems by taking into account patient characteristics and the scarcity of resources present in health services provision. This technique has been used to analyze problems related to healthcare resource management, but its possibilities to analyze larger problems related to population dynamics have been hardly explored. Traditionally, needs and demand for health services have been analyzed separately. In the present application, the response of the health system to both the population with need for surgery and to the patients included on a waiting list was analyzed.In this sense, the main contribution of this thesis is the application of discrete-event simulation to health services research from an epidemiologic point of view. Moreover, the model was statistically complex because the variety of sources and characteristics of data defining the main inputs and rules of the modeled system asked for a specific ad hoc methodology to collect and process them to generate the inputs that the simulation model needs. Therefore a relevant part of this work has been devoted to develop such input data analysis methodology.A discrete-event simulation model was built for needs and demand for cataract surgery in the Catalan public sector.The model reproduced the process of cataract surgery, from incidence of need for surgery, through demand, inclusion on a waiting list and surgery. The input data analysis methodology was described in detail. The model's parameters were estimated from several sources, including administrative and research databases.The implementation of the model in the software SIMUL8 and its link to Excel to make the model user-friendly for nonexpert users were described in detail. Several sensitivity analyses were performed to assess the impact of the variability of the input estimations (validation), the impact of different waiting list management strategies according to different scenarios of mean waiting time, and to assess the transferability of the methodology. Transferability was evaluated by applying the methodology for calculating the input values to different settings (other regions of Spain).Then, results of the model were used to analyze geographical variations of the impact of introducing a waiting list prioritization system. Moreover, information of the different regions was combined to use the model to assess the volume of need for cataract surgery in Spain according to different indication criteria for surgery. Transferability of the methodology to other elective surgeries was assessed by adapting the model to analyze needs and demand for knee replacement in Spain.Study of needs and demand for health services is important since substantial unmet needs are observed. The gap between needs and services provision may be too great to be resolved, but models that assess the impact of changes on the amount of resources used or the impact of health policies on the management of need and demand are useful in healthcare decision-making

New Technologies in Eye Surgery — A Challenge for Clinical, Therapeutic, and Eye Surgeons

Eye surgery is always progresses as the same way that the science advances. New emerging technologies such as bio-printing in 3D, developments and mathematical modeling in prototyping lab- on- a chip, visual implants, new biopolymers started to use in eye enucleation, detection of eye biomarkers at the cellular level, bio-sensors and new diagnostic tests should be considered to improve the quality of life of patients after surgery. This chapter provides a review of new and emerging technologies which are already working on global research centers. Emerging and converging technologies are terms used interchangeably to indicate the emergence and convergence of new technologies with demonstrated potential as disruptive technologies. Among them are: nanotechnology, biotechnology, information technology and communication, cognitive science, robotics, and artificial intelligence that have been launched as innovative products that promise to improve the quality of life and vision of patients with ocular compromised or low vision impairment. Some acronyms for these are: NBIC: Nanotechnology, Biotechnology, Information technology and Cognitive science. GNR: Genetics, Nanotechnology and Robotics. GRIN: Genetic, Robotic, Information, and Nanotechnology. BANG: Bits, Atoms, Neurons and Genes. Otherwise, to training ophthalmologist on news techniques, sophisticated simulation machines has been developing around the world

Biomechanics of Eye Globe and Methods of Its Study

Knowledge of biomechanical properties of eye globe is necessary both for correct selection of candidates for refractive surgery and right choice of operative intervention parameters. No less important, it is for corneal ectatic disease diagnostics and monitoring. Also it gives inestimable contribution for interpretation of intraocular pressure (IOP) indices especially in cases with irregular eye shape or after past corneal surgical procedures. Moreover, it allows studying injury mechanism by glaucoma process on optic nerve head fibers. Above it, scleral biomechanical properties research is necessary for the investigation of pathophysiologic factors of myopia manifestation and progression. This chapter is devoted to review of existed to date methods of study of eye fibrous tunic biomechanical properties. It describes mathematical, experimental, and clinical models provided evaluation of unsearchable by direct measurement parameters. It also observes effective technics of impact on both sclera and cornea with the aim of correction of its biomechanical condition