Cost-effectiveness in the Treatment of Glaucoma
Lowering intraocular pressure (IOP) is the standard treatment of glaucoma. Its effectiveness in halting glaucomatous progression in primary open angle glaucoma (POAG),1–3 ocular hypertension (OHT),4 and normal tension glaucoma (NTG)5,6 was confirmed by various randomized control trials (RTCs), whether by medication, laser treatment, or surgery. Management of primary angle closure glaucoma (PACG) is similar once the anterior chamber predisposition is reverted.7 Prevalence of glaucoma is expected to rise with the aging population, hence the cost of treating glaucoma. The cost is already creating substantial burden to public health worldwide. A cost-of-illness study—a type of health economical study that measures all the costs of a particular disease—showed that the US spent more than US$2.5 billion annually for glaucoma, of which US$1.9 billion was spent on direct costs and US$0.6 billion as indirect costs.8 Most cost-analysis studies concentrated on direct costs—medical consultations, diagnostic, follow-up investigations, and treatments. Since glaucoma is a disease of the elderly, the impact on productivity loss is relatively lower. Other indirect costs comprise time cost of care-givers, productivity loss from care-givers, and the societal costs of providing support to poorly sighted individuals. However, these are usually difficult to accurately quantify.
The cost of treating glaucoma increases with the severity of the disease. The annual cost of care per patient per year rose sharply from US$623 for early glaucoma to US$2,511 for advanced disease.9 Similarly, the estimated average annual maintenance cost of late-stage glaucoma in Europe was €803.10 For end-stage glaucoma, as much as 28 % of the total cost of care could be contributed to visual rehabilitation.11 The total financial burden attributed to glaucoma was calculated to be US$2.9 billion per annum in the US if productivity cost was also considered.12 Furthermore, the average healthcare cost per person in their first year of blindness was US$20,677 in the US.13 This is important because glaucoma is a leading cause of blindness globally, accounting for 12.3 % of the 37 million people with bilateral visual loss around the world in 2002.14 The World Health Organization (WHO) projected that the number of affected individuals would escalate to 80 million by 2020, 11.2 million of whom would suffer bilateral blindness attributable to the disease.15
Public healthcare systems have limited resources and could not provide exhaustive clinically beneficial interventions. In order to better allocate scarce health resources, calculating the cost for treatment of glaucoma is important. In health economic evaluation, all costs related to detection, management, and outcomes of treatment of the disease should be taken into account,16 since the ‘cost’ could represent an alternative benefit. There are several types of cost-analysis in healthcare. Cost minimization analysis is useful when the outcomes are expected to be the same across different options. In a cost-benefit analysis, both costs and benefits of the procedure under review are valued in monetary terms: the evaluation is thus based on the difference in inputs and outcomes in dollars. Another form of costbenefit analysis is cost-consequence analysis, which acknowledges the presence of different types of benefit that cannot be measured by a single unit. Cost-effectiveness analysis compares various resource implications of different healthcare interventions, and expresses the outcomes in common natural units. For instance, dollar per mmHg for IOP control. In cost-utility analysis, weight is given to the patient’s subjective level of wellbeing in different states of health. A quality-adjusted life year (QALY) is usually used in cost-utility analysis. This allows comparison of healthcare interventions across disease spectrums and healthcare specialties.
To estimate the therapeutic effect on chronic diseases like glaucoma, long-term data are required because monies are spent in advance and health benefits occur in the future. A RCT can only demonstrate the clinical efficacy of an intervention and might not truly reflect the management in a practical setting because they were guided by strict protocols and have a limited follow-up period. Therefore, mathematical models are utilized to aid analysis and provide an advantage in that it allows combined analysis of data from different sources in a meaningful way (e.g. systematic reviews and meta-analyses). Also, different influential factors could be varied in order to investigate a range of management scenarios.