CMS (2007) 4:59–83 DOI 10.1007/s10287-006-0008-x ORIGINAL PAPER Combined discrete-event simulation and ant colony optimisation approach for selecting optimal screening policies for diabetic retinopathy Sally C. Brailsford · Walter J. Gutjahr · Marion S. Rauner · Wolfgang Zeppelzauer Published online: 15 August 2006 © Springer-Verlag 2006 Abstract In this paper we present the first application to a healthcare prob- lem of discrete-event simulation (DES) embedded in an ant colony optimisation (ACO) model. We are concerned with choosing optimal screening policies for retinopathy, a sight-threatening complication of diabetes. The early signs of retinopathy can be detected by screening before the patient is aware of symp- toms, and blindness prevented by laser treatment. In this paper we describe the methodology used to combine the purpose-written DES model with the ACO algorithm. We simulate the effects of different screening strategies on a population of diabetic patients, and compare them in terms of two objective functions: Min C/E, cost-effectiveness (minimum incremental cost per year of sight saved, compared with a no-screening baseline) and Max E, maximum effectiveness (years of sight saved). We describe how ACO is used to optimise these two objectives, and discuss the issues involved in optimising stochastic variables. We present results for a range of different assumptions and scenarios about the format of screening programmes, using realistic data, and make policy recommendations on the basis of our findings. Keywords Screening for diabetic retinopathy · Discrete event simulation · Ant colony optimisation · Cost-effectiveness analysis · Decision-support system S. C. Brailsford (B ) School of Management, University of Southampton, Southampton S017 1BJ, UK e-mail: s.c.brailsford@soton.ac.uk W. J. Gutjahr Department of Statistics and Decision Support Systems, University of Vienna, Universitaetsstraße 5/9, 1010 Vienna, Austria e-mail: walter.gutjahr@univie.ac.at M. S. Rauner · W. Zeppelzauer University of Vienna, School of Business and Economics, Bruenner Str. 72, 1210 Vienna, Austria e-mail: marion.rauner@univie.ac.at