Economic evaluation in the form of reports of cost-effectiveness of the treatment and prevention of disease has only recently found widespread application in the visual sciences. While economic evaluation takes a number of forms: cost-minimization analysis, cost-benefit analysis, and cost-effectiveness analysis--it is the latter that is seen most often in the evaluation of vision-related health programs. Cost-effectiveness analysis is in particular seen most commonly in its very particular form of cost-utility analysis. Decision analysis is the analytic method most commonly used to perform cost-effectiveness analysis. In decision analysis, the expected cost and effectiveness of a health program are estimated in a rigorous fashion. In this report, we take the reader through the process of decision analysis including building the tree; populating the model with parameters for risk, cost and benefit; estimating expected cost and benefit; and deterministic and probabilistic sensitivity analysis. Examples employed include prominent studies of the cost-effectiveness of photodynamic therapy for treatment of neovascular macular degeneration and the treatment ocular hypertension to prevent glaucoma.