As in many published economic evaluation studies of screening programs and diagnostic tests in other areas of medicine, in this cost-effectiveness analysis only the costs and effects were considered that occurred up to the clinical end point diagnosis. For a more comprehensive evaluation of orthoptic vision screening, further studies should analyze the costs and effectiveness of treatment and the disability caused by visual deficits.
5 The definition of visual deficits could be linked to meaningful reductions of health-related quality of life for that purpose. The generic term amblyopia, which summarizes visual deficits of very distinct pathophysiologic origins, could be omitted in this perspective, as in this study. To make different studies comparable, dedicated software modules could be used to standardize results. The spreadsheet software developed for this study could be refined and used as a reference procedure for this purpose.
In this cost-effectiveness analysis, the alternative course of action with which orthoptic screening was compared was no orthoptic screening, which was associated with no costs and no effects until the chosen end point. In current practice, some of the cases detected by the screening program might have been detected by other means (and at other costs) at a later time had there been no orthoptic screening in kindergarten. To include this in an empiric study would require a far more extensive study design covering several years of individual follow-up. However, the chosen study design is very likely to yield a conservative estimate of the cost-effectiveness of orthoptic screening compared with study designs with a longer follow-up. Most other means of vision assessment tend to be less sensitive, less specific, and more costly than orthoptic screening, which would cause incremental CERs of orthoptic screening to be more favorable than the CER found in this study. In a recent evaluation of various methods of vision assessment performed by pediatricians in Germany,
18 the most favorable values found for sensitivity, specificity, and the proportion of inconclusive results were 54%, 78%, and 3%, respectively. By feeding these parameter values into the decision-analytic model introduced earlier,
27 the following can be shown: If all children in this study received pediatric vision assessment instead of orthoptic screening, the additional costs of orthoptic screening per additional case detected (incremental CER) compared with pediatric vision assessment would be less than the 924 Euro found in this study as soon as pediatric vision assessment cost more than only 4 Euro per child, assuming a prevalence of 2.5% as an example. This is mainly due to the low specificity of pediatric vision assessment causing many costly false-positive results. Thus, extending the empiric analysis to a time frame that includes a longer period of follow-up would be likely to yield an even more favorable incremental CER than found in this study.
In conclusion, this study provided data on the cost-effectiveness and its determinants of orthoptic vision screening in kindergarten. This information may be used by third-party payers such as health insurance or public health services when deciding about organizing and financing preschool vision-screening programs. Although we did not analyze the cost-effectiveness of treatment in this study, decision makers should take into account that treatment after early detection through screening potentially avoids a visual deficit that may last for almost a lifetime.