66 M.C.C. Lim and K.D. Frick

proportion of uncorrected refractive error; an economic rationale for governments to provide these is more likely to be justifiable.3,4

Myopia is often given minor priority in public health research, yet the societal costs of myopia can be considerable. In a broad view, costs include not only the costs of optical correction, but also morbidity resulting from eye diseases associated with myopia such as glaucoma, cataract, maculopathy and retinal detachment. As a first step, conducting a study that looks at only costs of the disease and treatment without considering alternatives is relatively simple to do. Studies that examine only costs of treating the disease can be either cost-of-illness or burden-of-disease studies. The former is concerned with costs from time of incidence, while the latter is concerned with the costs of treating prevalent cases regardless of time of incidence. These studies help to quantify the overall burden of a disease and allow comparisons with burdens of other diseases of the costs of the disease. Ultimately, economists prefer evaluations looking at both costs and benefits. With sufficient information, a full economic evaluation would look at costs and benefits of multiple alternatives.

The Economic Cost of Myopia: A Burden-of-Disease Study

At the simplest level, one could look into calculating the worldwide cost of correcting myopia, a burden-of-disease evaluation. Initially, the prevalence of myopia, or the number of myopes, must be estimated. The proportion of myopes paying for correction and unit price data are also needed to estimate the economic cost of myopia.

Annual cost of myopia = Number of paying myopes

×average amount spent per myope

=Population

×myopia prevalence

×proportion of myopes having correction

×proportion of myopes paying for correction

×average amount spent per myope.

(The reader should note that this is the “observed” burden. The “maximum” burden would include treatment of all myopes.)

67 The Economics of Myopia

Data needed include:

i.Prevalence of myopia

ii.Proportion of myopes with correction/paying for correction

iii.Amount paid for myopic correction

i.Prevalence of myopia

The data for this comes from the numerous epidemiological studies carried out around the world that have already been covered in detail in Chapter 1.1. However, data for many countries are still lacking. We will estimate the myopia prevalence in these countries based on data from neighboring countries or countries with similar socioeconomic characteristics.

China

China is country with the largest population in the world; it is important to use accurate figures for myopia prevalence. Numerous studies have been published recently. A population-based study of an urban cohort in Guangzhou, China, showed a prevalence of myopia of 32.3% in subjects aged 50 years and above.5 Urban 15-year-old school children had a myopia prevalence rate of 73%.6 Further, a study showed that 62.3% of 15-year-old Chinese school children in a rural area were myopic.7 Another study of rural school children in Southern China found that 37% of 13-year-olds were myopic, this figure rising to 54% of 17-year-olds, were myopic.8 The Beijing eye study showed that 22.9% of the population aged 40 to 90 years of age in a mixed urban and rural cohort were myopic.9 Table 1 shows an estimation of the number of myopes in China. For adults aged 44 years and above, data from the Beijing Eye Study9 was used because the mixed urban and rural cohort was more representative for the whole of the country than other purely urban or rural cohorts.

India

India is the country with the second largest population in the world. However, there are relatively few studies on myopia prevalence, which was estimated to be 7% in an urban cohort in 5- to15-year-olds10 and 4.1% of 7- to 15-year-olds in a rural cohort.11 In South India, it was 27% for those above 39-years of age.12 The estimates used are shown in Table 2.

Europe

The estimated prevalence of myopia in subjects 40 years and above in Western Europe is estimated at 26.6%, similar to that in the USA.13 From this we can assume that the myopia prevalence in those under 40 years of age is similar to that in our calculations, and the prevalence for the whole of Europe is assumed to be similar. The figure of 27% was used in our model and this is reasonable as it is similar to the figure we computed from more data, for the United States (see later). Assumptions such as these are necessary due to lack of data.

Singapore

There are several studies detailing the prevalence of myopia in Singapore and these are shown in Table 3.