The Economic Burden of Dry Eye Disease
The public health and economic burdens of dry eye disease can be characterized in a number of ways. The public health burden is typically protrayed by the prevalence of the condition, with details for specific subpopulations of interest. The economic burden is primarily described in terms of its impact on workplace productivity,1-3 medical care spending (either covered by a third party or out-of-pocket),1,4-7 and impact on health-related quality of life.2,8
In addition to understanding the economic consequences of dry eye disease, policy makers and those who develop and implement treatment guidelines must understand the tradeoffs to be made when using resources to treat or otherwise reduce the impact of the condition; this is referred to as the relative cost efficiency of the treatments.6,7
Public Health Burden
The most recent study of the economics of dry eye disease, conducted by Yu and colleagues, summarized and synthesized earlier work on the public health burden.1 The cited work included the Dry Eye Workshop in 2007 that indicated that the prevalence of dry eye disease could be as little as 3.5% and as much as 33.7%.1 The prevalence depended on the age considered and the diagnostic criteria used. The fact that the range spans an order of magnitude between the highest and lowest estimates contributes to the difficulty of establishing a precise estimate of the economic burden of dry eye disease.
Yu and colleagues’ analysis is not only the most recent, but also one of the highest quality studies of the economic burden of dry eye disease, despite the fact that their work relied on a decision-analytic model that was used to synthesize much of the earlier work.1 A decision-analytic model is a mathematical model used to represent the epidemiology, treatment recommendations and economics of the incidence and treatment of a disease. Models like these are frequently used to project the costs or assess the cost efficiency (discussed below) of treatment alternatives. While it can never represent the course of disease and decisions made during treatment with absolute certainty, this type of model is an accepted part of the literature.
Models like this frequently rely on assumptions about adherence to treatment recommendations. Yu and colleagues cited three sets of treatment guidelines from which they projected costs of care.
Although there is no universal definition of what model validation requires, a well-validated model will provide results that closely resemble reality for existing treatments or screening or the natural history of a condition. A validated model can then be used to project the effects of new treatments or to model potential long-term effects of existing treatments. For validation, Yu and colleagues compared the results of their model with published results that used a managed care database and found similar costs.1
In describing their model, Yu and colleagues assumed little change in treatment over a 1-year period, given little longitudinal data on dry eye disease.1 The reality of the small amount of data on longitudinal treatment patterns makes an estimate of the long-term effects of dry eye nearly impossible. For reference, 1 year is not very long in comparison with studies of diabetes or heart disease that often are projected for a lifetime.
When building and presenting a model, the analysts must note which costs and effects are included. Yu and colleagues reported results from both the societal and payor perspectives, where the term “perspective” indicates whose costs and whose benefits matter.1 The societal perspective attempts to describe all relevant costs and benefits. The payor perspective is much more narrow and likely more relevant to the decision maker. An analysis from the payor perspective addresses the question of how much money will be saved with a new treatment regimen compared with the status quo or how much more money must be spent to buy better health outcomes.
Yu and colleagues used an online survey to gather data on characteristics of dry eye disease, health care utilization and workplace productivity.1 The workplace productivity loss was measured in terms of both absenteeism (missed work) and presenteeism (a lack of productivity while at work).1 The cost of treatment was assessed for ocular lubricants (using the price per drop assuming a certain drop size and using reports of adherence rates), for cyclosporine (also including adherence rates), punctal plugs, nutritional supplements and visiting a health care professional.1
In the study, health-related quality of life is manifested primarily through reduced workplace productivity loss (on the assumption that individuals want to feel productive).1 Quality-of-life improvement was not measured directly. The combination of using the most up-to-date data on prevalence and treatment and the use of novel data on health care utilization and workplace productivity make the Yu study the highest quality to date.
The study results suggest that annual direct costs (i.e., medical care treatment costs) were $678 for patients with mild dry eye symptoms, $771 for patients with moderate dry eye symptoms, and $1,267 for patients with severe dry eye symptoms.1 Given the estimated prevalence of the condition, total annual direct costs of dry eye disease were estimated at $3.8 billion.1 This figure is not minor, but it is relatively small portion of the multi-trillion-dollar healthcare spending in the United States.
The detailed figures on direct medical care costs indicate that for patients not using cyclosporine and punctal plugs, office visits account for a large fraction of medical care expenses. For those with severe dry eye, office visits account for the majority of direct medical care costs for all groups that do not use cyclosporineeven outweighing the cost of punctal plugs.1
Medical care costs associated with dry eye disease are small relative to the costs of lost productivity (often referred to as indirect costs). Those with mild, moderate and severe dry eye symptoms experience $12,686, $12,569 and $18,168 of annual productivity loss, respectively.1 Even for mild and moderate cases, this is nearly the same as losing a full-time equivalent minimum-wage worker. These figures are an order of magnitude larger than the medical care costs and make up a substantial portion of the estimated $55.4 billion total impact on the United States economy.1
Friedman also argued for the importance of considering quality of life measures.2 A lack of concordance between objective measures of symptoms and self-reported measures of quality of life has been noted.8 Since perceived quality of life motivates behavior, Friedman notes that the availability of some measure of quality of life is important for clinicians managing the condition for patients.2 The quality-of-life measures have demonstrated that there is a decreased ability to perform activities of daily living and that the impact on health utility (the metric for calculating quality-adjusted life-years) is similar to that of mild psoriasis and moderate to severe angina.2,3
Cost Efficiency of Treatments
Cost efficiency can be characterized using a number of criteria. The simplest comparison to assess economic efficiency is the result of a cost-benefit analysis. In such an analysis, the dollar value of the benefits of a treatment is compared with the dollar value of the costs of the treatment. If the dollar value of the benefits is bigger, the treatment may make sense. However, placing a dollar value on the effects of treating dry eye is not trivial. We either have to be able to measure precisely how much productivity improves when the conditions are treated or the dollar value of symptom relief in terms of quality-of-life improvement.
In other cases, investigators use a cost-utility analysis in which they compare the costs to the quality-adjusted life-years (QALYs) gained. While there is no universal agreement on how to measure quality of life, there is at least a generally agreed on standard for how much it is worth to spend to gain QALYs.
Other cost-effectiveness analyses use outcomes other than QALYs. These analyses are simpler because the outcome measurement is more straightforward, but there is less agreement as to how much it is worth to spend to increase the number of “responders” to treatment.
Finally, we may try to characterize a set of outcomes to compare with the costs. The challenge of interpreting a cost-consequence analysis is that the costs must be compared against multiple criteria; no single criterion will be appropriate in all circumstances. In addition, the values for each criterion, let alone the combination of all of them, are rarely obvious.
Given the relatively low direct costs of treating dry eye disease, with its important impact on health utility, studies have found treating the condition to be cost effective (i.e., less expensive to gain QALYs than an accepted threshold).6,7 Investigators modeling Refresh Tears and Systane found that Systane was both more effective and more expensive but that the increased cost was worth spending for the effect gained.6 Systane cost only $5,837 extra to gain the equivalent of a year with maximum quality of life (1 QALY).6 This unit price is less than what is considered reasonable, $50,000 per QALY. Similarly, Brown and colleagues found that topical cyclosporine 0.05% costs nearly $35,000 per QALY gaineda considerably more expensive unit price, but less than the $50,000 per QALY unit price commonly cited as a threshold.7
Other Eye Conditions
Although there are a relatively small number of studies of the economics of dry eye, comparisons can be made with more-frequently studied conditions including cataract,9 glaucoma10 and age-related macular degeneration.11 A review of cataract studies focused on the cost effectiveness of first eye surgery in both Western and non-Western countries and found these procedures to be universally relatively cost effective.9 A review of glaucoma studies reported on the costs of treating glaucoma in the United States, Canada and Europe, finding that while the estimated magnitude of the costs is highly variable, advanced glaucoma is associated with higher costs.10 For age-related macular degeneration, Foster and colleagues evaluated the quality of 24 economic studies that met strict eligibility criteria and found the quality of the literature to be suboptimal.11
Thus, even for eye conditions with a larger number of associated studies, the results are not always ideal for setting policy or recommending treatment guidelines with a consideration of the economics of the condition.
Evaluating specific types of utilization is an area of research that is in its infancy. More studies using claims data will need to be undertaken, and even then the reason for the physician visits may not be entirely clear.5,12
In some databases, while there are unique identifiers for providers, the specialty of the provider is not always obvious, and the coding for the visit may reflect multiple diagnoses. In addition, dry eye has multiple causes. Sjögren’s syndrome, as an example, is also associated with other symptoms that may be associated with utilization, and separating the costs attributable to dry eye from the costs attributable to other symptoms may be difficult.13-15 n
- Yu J, Asche CV, Fairchild CJ. The economic burden of dry eye disease in the United States: a decision tree analysis. Cornea. 2011;30(4):379-387.
- Friedman NJ. Impact of dry eye disease and treatment on quality of life. Curr Opin Ophthalmol. 2010;21(4):310-316.
- Pflugfelder SC. Prevalence, burden, and pharmacoeconomics of dry eye disease. Am J Manag Care. 2008;14(3 Suppl):S102-S106.
- Enzenauer RW, Kao A, Williams T, et al. Relative costs of various preserved artificial tear solutions for the treatment of dry eye conditions. Eye Contact Lens. 2003;29(4):238-240.
- Fiscella RG, Lee JT, Walt JG, et al. Utilization characteristics of topical cycolsporine and punctal plugs in a managed care database. Am J Manag Care. 2008;14(3Suppl):S107-S112.
- Wlodarczyk J, Fairchild C. United States cost-effectiveness study of two dry eye ophthalmic lubricants. Ophthalmic Epidemiol. 2009;16(1):22-30.
- Brown MM, Brown GC, Brown HC, et al. Value-based medicine, comparative effectiveness, and cost-effectiveness analysis of topical cyclosporine for the treatment of dry eye syndrome. Arch Ophthalmol. 2009;127(2):146-152.
- Mizuno Y, Yamada M, Miyake Y; Dry Eye Survey Group of the National Hospital Organization of Japan. Association between clinical diagnostic tests and health-related quality of life surveys in patients with dry eye syndrome. Jpn J Ophthalmol. 2010;54(4): 259-265.
- Agarwal A, Kumar DA. Cost-effectiveness of cataract surgery. Curr Opin Ophthalmol. 2011;22:15-18.
- Fiscella RG, Lee J, Davis EJ, et al. Cost of illness of glaucoma: a critical and systematic review. Pharmacoeconomics. 2009;27(3):189-198.
- Foster WJ, Tufail W, Issa AM. The quality of pharmacoeconomic evaluations of age-related macular degeneration therapeutics: a systematic review and quantitative appraisal of the evidence. Br J Ophthalmol. 2010 Sept;94(9):1118-1126.
- Chiang TH, Walt JG, McMahon JP Jr, et al. Real-world utilization patterns of cyclosporine ophthalmic emulsion 0.05% within managed care. Can J Clin Pharmacol. 2007;14(2):e240-e245.
- Callaghan R, Prabu A, Allan RB, et al. UK Sjögren's Interest Group. Direct healthcare costs and predictors of costs in patients with primary Sjogren's syndrome. Rheumatology (Oxford). 2007;46(1):105-111.
- Segal B, Bowman SJ, Fox PC, et al. Primary Sjögren's Syndrome: health experiences and predictors of health quality among patients in the United States. Health Qual Life Outcomes. 2009 May;7:46.
- Bowman SJ, St Pierre Y, Sutcliffe N, et al. Estimating indirect costs in primary Sjögren's syndrome. J Rheumatol. 2010;37(5):1010-1015.