A pilot cost-benefit analysis of a children's spectacle reimbursement scheme: Evidence for Including children's spectacles in Mongolia's Social Health Insurance.

BACKGROUND AND AIM: Globally, 12.8 million children have vision impairment due to uncorrected refractive error (URE). In Mongolia, one in five children needs but do not have access to spectacles. This pilot cost-benefit analysis aims to estimate the net benefits of a children's spectacles reimbursement scheme in Mongolia.
METHODS: A willingness-to-pay (WTP) survey using the contingent valuation method was administered to rural and urban Mongolia respondents. The survey assessed WTP in additional annual taxes for any child with refractive error to be provided government-subsidised spectacles. Net benefits were then calculated based on mean WTP (i.e. benefit) and cost of spectacles.
RESULTS: The survey recruited 50 respondents (mean age 40.2 ± 9.86 years; 78.0% women; 100% response rate) from rural and urban Mongolia. Mean WTP was US$24.00 ± 5.15 (95% CI US$22.55 to 25.35). The average cost of a pair of spectacles in Mongolia is US$15.00. Subtracting the average cost of spectacles from mean WTP yielded a mean positive net benefit of US$9.00.
CONCLUSION: A spectacle reimbursement scheme is potentially a cost-effective intervention to address childhood vision impairment due to URE in Mongolia. These preliminary findings support the proposal of the inclusion of children's spectacles into existing Social Health Insurance. A much larger random sample could be employed in future research to increase the precision and generalisability of findings.

Introduction

Uncorrected refractive error (URE) accounts for 61% of the total global burden of vision impairment (VI) [1], and affects 12.8 million children worldwide [2]. Despite the existence of evidence-based and cost-effective strategies, limited affordability and access to high-quality refractive services remain the major barriers to better spectacles coverage in low- and middle-income countries [3-5]. Delivery of spectacles is shown to improve cognitive development, educational achievement, work productivity, and psychosocial well-being [6-10]. The annual global economic loss caused by VI due to URE is estimated to be US$202 billion [11].

Mongolia, the least densely populated nation on earth (2 people/km2), is a landlocked country in North-Central Asia [12]. The Mongolian government provides citizens universal access to health care services covered under Social Health Insurance (SHI) [13], and children receive free at point of use health and dental care [14,15]. However, SHI does not cover spectacles, despite their inclusion on the World Health Organisation (WHO) Priority Assistive Product List [16]. According to the Mongolian Resolution for the National Non-communicable Disease Programme, more than 90% of Mongolian children with VI due to URE do not have spectacles [17]. Given the urgency to address the burden of URE among children, there is a natural interest in a children’s spectacle reimbursement scheme for Mongolia.

Ready-made spectacles are offered with lenses of the same spherical prescription in both eyes, while custom spectacles can be offered with combination of prescriptions to correct any magnitude of refractive errors (RE). Studies suggest that low cost, ready-made spectacles are effective at correcting RE, without compromising spectacle wear while reducing costs and solving logistical challenges of school-based refractive service programmes [18,19]. The number of children who can benefit from a pair of ready-made spectacles is high in China [20], India [18], and Cambodia [21], which ranges from 70–83%. Based on a global dataset obtained from a screening programme supported by an international eye non-governmental organisation (NGO), 51.4% of Mongolian children were deemed clinically suitable for ready-made spectacles (OneSight, 2021).

To inform policymakers of the potential benefits of such a scheme, a cost-benefit analysis (CBA) is preferable over other health economic analyses because CBA reports outcomes in monetary terms, which are easily presented to decision-makers [22]. Langabeer et al.’s CBA on telemedicine demonstrates potential annual savings of US$928,000 in Houston, United States, when compared to traditional emergency medical services [23]. A willingness-to-pay (WTP) survey is one way in which preferences can be elicited for use in CBA that can hypothetically estimate an intervention’s benefits [24]. It assesses how much a target population is willing to pay for an intervention. WTP has been used to estimate the potential value of a proposed spectacle delivery scheme in rural Cambodia [25].

The Mongolian SHI is largely funded by the state central budget through general taxation. Should the proposed child’s spectacle reimbursement scheme be adopted by the government, the SHI would cover the reimbursement cost of eye examination and children’s spectacles [26]. However, the actual framework for the reimbursement scheme is yet to be structured. The exploration of such a framework will be in our future scale-up study.

Despite a growing number of economic evaluation studies on URE programmes, few studies are on children. This pilot CBA is designed to assist eye health NGO Orbis International to provide initial findings to the Mongolian policymakers of the potential benefits of a proposed child’s spectacle reimbursement scheme.

Materials and methods

This pilot study was approved by the Faculty of Medicine, Health and Life Sciences Research Ethics Committee, Queen’s University Belfast (reference number MLHS 20_73). The study protocol was reviewed by the local gatekeeper, Mongolian Ophthalmologist’s Society, and assured its adherence to the Mongolia’s ethics regulations (reference number MOS_04). Verbal consent was obtained from each respondent upon agreeing to participate in the survey.

Design and setting

A WTP survey of rural and urban Mongolia was used to estimate the benefits of providing spectacles to any children with RE. Those estimated benefits were used in the CBA.

Sampling

This study used a trained local Mongolian-speaking enumerator to recruit 50 taxpayers, who were parents of children participating in a school-based vision screening programme conducted by Orbis International and OneSight (both are eye health NGOs). According to the central limit theorem for sample size of more than 30 [27], the sampling distribution was assumed to be normal. Upon discussions with the local researchers, we increased the sample size to 50 parents as a contingency to a high non-response rate. Parents from the Orbis contact list were randomly selected where samples were clustered into rural and urban schools. Criterion sampling was employed to recruit (i) 12 parents of children who do not need spectacles living in rural settings and 13 from urban settings, (ii) 12 parents of children who were provided with spectacles living in rural settings and 13 from urban settings.

Willingness-to-pay survey

A triple-bounded-dichotomous-choice experiment (TBDC) was used to facilitate value elicitation by leading respondents logically through consideration of their WTP [28]. The market cost of a pair of spectacles in Mongolia was used to determine realistic starting bids. The average cost of a pair of ready-made spectacles of US$5.00 (MNT15,000) and the cost of custom spectacles of US$25.00 (MNT75,000) were used to inform bids [29]. After discussions with local eye care personnel as to their impressions of what might be reasonable, three starting bids were established: a low bid—US$12.50, medium bid—US$17.50, and high bid—US$22.50. The subsequent bids were dependent on the acceptance (Yes) or rejection (No) of the former bid. In the case of respondents offering no maximum limit, the maximum WTP amount of US$30.00 was taken. To reduce anchoring bias, the starting bid used to initiate the survey was randomly selected [30] (Fig 1).

Fig 1

Schematic representation of triple-bounded-dichotomous-choice experiment.

*Respondents were asked how much would they be willing to pay in additional taxes per year for any child who needs spectacles to have access to it.

Costs of spectacles

Three costs for spectacles were used to calculate the scheme’s net benefits: US$5.00 for ready-made spectacles, US$25.00 for custom spectacles, and US$15.00 for spectacles with an equal probability of being either. Based on a dataset obtained from an outreach vision screening programme initiated by an international eye NGO, one in two Mongolian children who had refractive error can be corrected effectively from a pair of inexpensive, ready-made spectacles. Therefore, the costs of ready-made spectacles and custom spectacles were used to construct the cost of a mixed offering to reflect the need for a combination of both spectacles types to address the refractive needs of the children.

Data collection

Due to COVID-19 safety considerations, data were collected via telephone survey. To ensure data quality and consistency, the trained enumerator used a standard script when conducting the survey. Demographic details such as sex, age, and educational level were collected. Subsequently, three closed-ended questions were asked: (a) “Are you willing to pay [an amount] in additional taxes per year for any child who needs spectacles to have access to it?”, followed by (b) “What if the amount is [an amount either higher/lower depending on previous response], would you be willing to pay?”, followed by (c) “And lastly, what if the amount is [an amount either higher/lower depending on previous response], would you be willing to pay?”.

Fig 2 shows a questions route using the medium starting bid, US$17.50, as an example. We referred the approach adopted by Islam et al. in eliciting the final WTP [29]. If the respondent was willing to pay US$17.50 (responded Yes), a higher bid was offered at the second question–US$22.50; if the respondent was not willing to pay US$17.50 (responded No), a lower bid was offered at the second question–US$12.50. The second and third question applied the same approach to arrive at the final WTP.

Fig 2

Survey questions route, using starting bid of US$17.50 as an example.

Considering that children required annual prescription changes, the survey questions were structured to ask taxpayers how much additional annual taxes they would be willing to offer to cover the reimbursement. The WTP estimation was assumed to be conservative because if the spectacles can last more than a year, the amount paid by the taxpayers would be exceeding the costs.

Data management and statistical analysis

Statistical Package for the Social Sciences V25 (SPSS Inc., Chicago, IL) was used for data management and analysis. Data were cleaned and checked for consistency. Because we met the criterion of central limit theorem, parametric methods were adopted for its greater statistical power and ability to use 95% confidence intervals (CI) [31].

The study’s primary outcome was the net benefits of a children’s spectacle reimbursement scheme. The benefit in our study was determined using respondents’ annual WTP for children’s spectacles [32]. We assumed that the elements of benefit might include the aspect of additional lifetime income that can be attributed to the higher trajectory in earnings when the child is corrected with spectacles as URE has shown to have reduced the future income or increase children’s educational inequalities [33]. The cost in our study was assumed to be that of ready-made spectacles, custom spectacles and a mix of these two types of spectacles in equal proportions. Net benefit was calculated by subtracting the cost of a pair of spectacles from the mean taxpayer’s WTP. A positive net benefit means the benefit outweighs the cost, while a negative net benefit means that cost outweighs the benefit. Descriptive analysis was performed to obtain the mean WTP with standard deviation (SD) along with 95% CI. The differences in demographic characteristics among respondents in rural and urban Mongolia were tested using Chi-square test for categorical variables, and t-test for continuous variables, with a significance level of 5%.

The association of mean WTP with predictor variables, including geographic setting, age, sex, educational level, and children’s RE status (those with a child or children prescribed spectacles due to RE versus those with children not needing spectacles), were assessed using t-test and ANOVA.

Results

Participants’ demographic profiles

All persons contacted (mean age 40.2 ± 9.86 years; 78.0% female) agreed to participate in the survey (n = 50, response rate = 100%). There was no statistical difference between respondents’ mean age (p = 0.411), sex (p = 0.172), and educational levels (p = 1.00) in rural and urban settings. Among all respondents, more than two-thirds (84.0%) were below age 50 years, and over 90.0% completed either secondary or tertiary level education (Table 1).

Table 1

Demographic characteristics of survey respondents.

	RuralN (%)	UrbanN (%)	TotalN (%)	P-value comparing rural and urban respondents
Sex    Female    Male	22 (88.0%)3 (12.0%)	17 (68.0%)8 (32.0%)	39 (78.0%)11 (22.0%)	0.172*
Age (years)    20–35    36–50    ≥ 51Mean Age ± SD (years)	12 (48.0%)10 (40.0%)3 (12.0%)39.0 ± 10.2	11 (46.0%)9 (36.0%)5 (20.0%)41.3 ± 9.60	23 (46.0%)19 (38.0%)8 (16.0%)40.2 ± 9.86	0.862**0.411***
Educational level    Illiterate    Primary    Secondary    Tertiary	1 (4.00%)2 (8.00%)11 (44.0%)11 (44.0%)	-1 (4.00%)12 (48.0%)12 (48.0%)	1 (2.00%)3 (6.00%)23 (46.0%)23 (46.0%)	1.00**
Total	25 (100%)	25 (100%)	50 (100%)

* Yates Continuity Correction test was selected as a 2x2 table was assessed.

** Fisher’s Exact Test was selected as expected cell values <5.

*** t-test.

Cost-benefit analysis

The mean amount respondents were willing to pay in additional annual taxes for any child with RE to get a pair of free spectacles was US$24.00 ± 5.15 (95% CI US$22.55 to 25.35). Table 2 shows the calculation of net benefits. The calculations for ready-made spectacle revealed a positive net benefit of US$19.00. For custom spectacles, calculations found a negative net benefit of US$1.00. An analysis of the cost of mixed provision of spectacles found a positive net benefit of US$9.00, with benefits 1.6 times outweighing the cost.

Table 2

Net benefits calculation.

	Ready-made spectacles	Custom spectacles	Mixedspectacles
Cost (US$)	5.00	25.00	15.00
Benefits* (US$)	24.00	24.00	24.00
Net Benefits (US$)	+19.00	-1.00	+9.00
Benefits-to-Cost ratio	4.8: 1.0	0.96: 1.0	1.6: 1.0

* As estimated by mean willingness-to-pay.

Factors associated with willingness-to-pay

Respondents of children with RE (US$22.50 ± 5.34) offered significantly less than those having children without RE (US$25.63 ± 4.50, p = 0.031). There was no significant difference between WTP of rural compared to urban respondents (p = 0.685), nor did WTP differ by age (p = 0.423), sex (p = 0.166) or educational level (p = 0.273) (Table 3).

Table 3

Potential predictors of mean willingness-to-pay (WTP).

	Mean willingness-to-pay (WTP)US$ ± SD	P-value comparing groups
Setting    Rural    Urban	24.30 ± 5.2823.70 ± 5.11	0.685*
Sex    Female    Male	23.46 ± 5.4325.91 ± 3.58	0.166*
Age (years)    20–35    36–50    ≥ 51	24.67 ± 5.1324.08 ± 4.5821.88 ± 6.51	0.423**
Educational level    Illiterate    Primary    Secondary    Tertiary	15.00***23.33 ± 7.6423.59 ± 5.5324.89 ± 4.30	0.273**
Children withrefractive errors    No    Yes	25.63 ± 4.5022.50 ± 5.34	0.031*

* t-test.

** ANOVA.

*** Only one participant.

Discussion

We found a positive net benefit of US$9.00 in this CBA of a children’s reimbursement scheme with equal probability of uptake of custom spectacles as opposed to ready-made spectacles. The mean WTP is independent of respondents’ demographic characteristics, except children’s RE status. Perhaps unexpectedly, parents of children without RE had significantly higher WTP in additional annual taxes for any child with RE to get spectacles than did parents of affected children might be influenced by variable such as income level that we did not include in the study.

The mean WTP in urban (US$23.70) and rural (US$24.30) settings in Mongolia are both higher than those found in a recent study assessing parental WTP for children’s spectacles in Cambodia (US$18.60 and US$13.90 in the capital and rural settings, respectively) [34]. The observation of Cambodian respondents in offering lower WTP can be explained by the following reasons. Firstly, the proposed scheme in Mongolia was to include spectacle provision through the Social Health Insurance which will not incur any payment at the service point, while in Cambodia, the proposed cross-subsidisation scheme will require parents to pay a nominal amount. Secondly, the difference may be due to a higher gross domestic product per capita in Mongolia than Cambodia (US$4,339 versus US$1,643) [35,36]. Lastly, our study uses additional annual taxes as the payment vehicle, while in Cambodia, the payment was through out-of-pocket expenses.

Several studies demonstrate that exposure to “health shocks”, such as the loss of vision associated with URE, can increase WTP [29,37]. In Cambodia, parents of children with refractive error were willing to pay a significantly higher amount (US$17.50 or more) than parents who were unaware of their children’s RE status [34]. Interestingly, in our study, respondents having children with RE had a lower WTP than respondents of children without. It may relate to unobserved heterogeneity related to income, for example, those with RE having lower income in our sample. This should be examined in further research with a larger sample and where details of income are collected.

Were only ready-made spectacles offered our study suggests a positive net benefit (US$19.00) while were only custom spectacles offered our study suggests a slightly negative net benefit (US$1.00). This suggests the benefits outweigh the costs of providing inexpensive ready-made spectacles but not custom spectacles. Concerning this, one proposed strategy would be for parents to “top-up” the government-subsidised spectacles when the cost of spectacles exceeds the subsidised amount. For example, if the government subsidises US$10.00 for any type of spectacles, parents will have to pay for the additional costs. This is especially referring to custom spectacles where the cost is often higher than the ready-made spectacles. A feasible structure of the reimbursement framework will be explored in our future research.

WTP has been widely used in the eye care sector to aid in service delivery planning, such as scheme for the cross-subsidisation of cataract surgery or spectacles [29,34,38]. We used WTP to estimate the potential benefits to inform a CBA, a novel approach in evaluating interventions related to children’s URE. Due to limited resources and high demand for children’s refractive services in Mongolia, policymakers must be informed of the value added by the intervention. This pilot CBA and future scale-up analysis should serve as a reference for the Mongolian government in making an informed policy decision.

The purpose of including children’s spectacles into Social Health Insurance is to allow children who had URE access to spectacles without facing financial hardship, thus reducing the burden of VI due to URE. While we found no studies exploring the barriers to the provision of spectacles in Mongolia, based on the available literature, we assume that the following factors were associated with the significant burden. Firstly, Mongolia has a limited workforce that can deliver paediatric eye examination and spectacles dispensing [39]. Mountainous and upland steppe and semi-desert geography territories of Mongolia make children who live in rural unable to access eye health services and to procure spectacles in cities [40]. Lastly, approximately one-third of the Mongolian population was living below the poverty line [41], where the cost of spectacles might be a financial burden for them. To inform policymakers and advocate a reimbursement scheme for children’s spectacles, we recommend exploration of these barriers should be included in the scale-up study.

Strengths of the current study include our having used a number of approaches recommended to increase the validity of the contingent valuation estimates: (i) using telephone interviews instead of surveys posted by mail; (ii) using WTP rather than willingness-to-accept; (iii) pretesting the survey before actual interviews; (iv) phrasing the WTP questions in a hypothetical scenario by indicating additional taxes that respondents would have to pay to subsidise free spectacles; and (v) collecting respondents’ demographic characteristics [42].

Limitations of the study must also be acknowledged. The relatively small sample size may explain the lack of a significant association between WTP and most demographic factors. Secondly, hypothetical WTP surveys using contingent valuation may be prone to overestimation of the actual WTP amount [43]. Further, it has been suggested that a visual aid should be used when possible in WTP studies, so that biases due to miscomprehension can be avoided when participants are asked to make decisions about unfamiliar subjects [24]. We originally planned to present visual aids demonstrating to respondents the impact of spectacle wear. However, COVID-19 precautions made face-to-face interviews and the use of such aids impossible. In addition, employing the costs of ready-made spectacles and custom spectacles to construct the cost of a mixed offering may have also confounded the results, but we felt it was necessary to reflect the local refractive needs. Finally, despite including respondents whose children participated in the vision screening programme in rural and urban schools (Orbis International’s contact list), we did not include in our sample individuals not involved in the screening programme. This might cause selection bias and thus affecting the generalisability of the findings.

For recommendations, we suggest employing a random sampling method and sample size power calculation in future upscaling study. An open-ended final WTP question should also be included to obtain a more accurate estimation of the mean WTP and to address issues that might arise with censoring the maximum value at US$30. We only included variables such as parent’s age, sex, educational level, resident location, and children’s RE status in testing factors associated with WTP. The status of parent’s income could be a key indicator that should be included, as demonstrated by other studies which found to be significantly correlated with the final WTP [34,44,45].

Despite its limitations, our analysis is one of the few examining the cost-benefit of national programmes providing spectacles for children. Our preliminary findings suggest that there is potential to include children’s spectacles into the existing Social Health Insurance. However, further research with larger sample size is needed to confirm this.

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Reviewer #1: The cost-benefits analysis (CBA) of implementing the proposed cost reimbursement scheme for child’s spectacle sounds great. However, the paper should talk about the hypothetical WTP cost for spectacles and the saving it will make for the individual, society or government provided that there is a multi-tier spectacle scheme system in place, where capable pay higher charges for the same spectacle as they stated willing to pay while poor pay small amount. The detail of the scheme is important to discuss stating how this works for both families and government.

Having just WTP findings cannot hypothetically estimate the benefits of the proposed spectacle reimbursement scheme. How much money family/government save can be stated by WTP results, but it does not the give the monetary value of benefits (impacts of having the scheme)? CBA is not only about knowing the cost but also measuring the benefit by that cost. The later part is not covered in the paper. My question is why do authors need to say CBA? Why not just say a WTP study and report the findings and discuss the potential benefits?

If this is about the scheme to be launched by the government, it would be the compulsory service launched by the government in a public health system, which make richer pay high cost for the same product and poor pay less. If the parents would be willing to pay high amount of money for the spectacles, they would rather choose custom-made and high-quality spectacles that they can afford. Why would they need such scheme? The simple approach would be that the government can give the rebate if the annual income is low. Why to pay tax for the service or product which they may not require?

Yet one another question, if authors found parents are willing to pay high, why 90% of children do not have spectacles for URE in Mongolia (reference 17) as stated in the introduction. Literatures also suggest that the ready-made spectacles are useful and beneficial to small number of populations. Majority would need custom-made spectacles. The use and importance of ready-made spectacles are mainly for the resource poor settings where the refraction services and custom-made options are not available, inaccessible or unaffordable. Is this the situation in Mongolia?

To highlight the benefits and implication/ significance of the scheme, the paper should explain about the proposed child’s spectacles reimbursement scheme? Who is proposing this scheme and what are the details of this scheme should be explained in the introduction?

The sample size is too low to look at the association with the factors mentioned in the paper. I recommend referring this as a pilot study and not describing as a cost benefit analysis as the endpoint beneficiary group is not clear based on the inclusion of study participants (taxpayers only). As reported in strength of the current study in discussion - If additional taxes would have to be paid to subsidise free spectacles, why would these participants do so? They will/can purchase the spectacles straightforward rather than through the proposed scheme.

Design and setting section in methods state that WTP survey was used to estimate the benefits of providing spectacles to any children with RE. But the results only talk about cost of the product and WTP.

Sampling – target participants are taxpayers. Do you mean there are also people who do not pay tax because of low-income threshold? What is the income threshold level to whom this scheme is beneficial? If the problem is with those who cannot afford (who are not participants in the study), how this scheme would work is not clear?

How was sample size of 50 participants determined? It is very low for any epidemiological or population-based study. This number is ideal for a pilot study before a main or large sample study. Why not say this a pilot study (state in title and objective)? What do you mean to sampling distribution was assumed to be normal?

What is the basis for determining these bids figure $12.50, $17.50 or $22.50? It seems these were chosen to fit in the middle range of ready-made and custom-made spectacles. What proportions were ready to pay $12.50? What percentage were ready to pay $30? Why high- end of this bid is $30? It seems there are still high numbers of participants who would have been reporting that they are willing to pay high. Why not a last question was introduced to report the maximum amount they are willing to pay? It also sounds illogical to base on unpublished study.

Results/Discussion: The results are reported according to the methods mentioned. However, it should address the comments and questions raised above on the study methodology.

There is a positive net benefit of $9 to whom? Government or parents? How is this beneficial to those who are willing to pay higher price than average custom-made spectacles cost? Yes, the beneficiary group would be the lower income threshold families, who are not part of the study? It would have been clear if family income was collected, and income was analysed as a factor to relate the association.

Reviewer #2: Thank you for the opportunity to review this wonderful manuscript. This is well-constructed research with excellent writing. This study provides interesting new information to readers of PLOSONE and also to policymakers in Mongolia. I agree with authors on the strengths and acknowledge limitations of this study. Some specific comments noted below:

1. I am curious to see how the response will be if we explain the benefit of spectacles wear prior to questions about WTP since not everyone understands the importance of glasses.

2. Any other explanation on why parents of children have refractive error WTP is less than parents of children have no refractive error. Is this possible that those parents who have children with refractive error have better idea about the cost of glasses?

3. About the potential predictors of WTP, can parent’s income be one of the confounding factor?

4. "90% of Mongolian children with VI due to URE do not have spectacles". That number is significant, and the study focuses mainly on the cost-benefit of glasses. Is there anything else lead to this number, can it be accessibility of eye care services or something else? I think if we can address and recommend in future study that would be great resource for policymakers.

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Reviewer #1: Yes: Prakash Paudel

Reviewer #2: Yes: Anh Vinh Bui

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9 Feb 2022

Responses to Academic Editor:

1. The authors should pay particular attention to Reviewer 1 comments, clarifying the study design and reflect on whether the commentary overreaches the actual scope of the work. Response: We thank you for your suggestion. We addressed the above-mentioned concerns in our revised manuscript.

2. Please also give further detail on the level of unmet visual need in Mongolia, and refractive services that are possible. This impacts on the question of the validity of ready-made spectacles as a means to meet demand in Mongolia.

Response: Published literature on the burden of unmet visual needs in Mongolia is limited. A study [1] showed that the prevalence of myopia among children in Mongolia was 5.8%, and according to the Resolution adopted by the Mongolian government on non-communicable diseases, 90% of children with refractive error did not own a pair of spectacles.[1] The burden of visual needs is exacerbated by the limited workforce for refractive services as there is limited optometry capacity in the country.[2] To address this challenge, ORBIS collaborated with the National Centre for Maternal and Child Health in Mongolia launched a 4-year programme (Model of Excellence in Modern Ophthalmology in Mongolia) to build local capacity by training ophthalmologists in urban and rural hospitals to perform refraction and dispense spectacles for children. We included the above information in the Introduction and Discussion.

3. Finally, please given further information on determination of sample size.

Response: The sample size was built upon the assumption that 30 or more participants will meet the principle of the central limit theorem, and therefore parametric test could be performed.[3] According to the central limit theorem, sampling distribution is considered normal with a minimum sample size of 30, in which sample mean will be closely gathered around the population mean. In Methods, we included a sentence like this - “According to the central limit theorem for sample size of more than 30, the sampling distribution was assumed to be normal. Upon discussions with the local researchers, we increase the sample size to 50 parents to avoid a high non-response rate.”

4. Thank you for stating the following in the Competing Interests/Financial Disclosure * (delete as necessary) section:

"I have read the journal's policy and the authors of this manuscript have the following competing interests: Professor Congdon declares that he is the Director of Research for Orbis International, Dr Chuluunkhuu declares that she is the Country Director for Orbis Mongolia, and Tai Stephan declares that she is the Global Programme Manager for Orbis International". We note that you received funding from a commercial source: Orbis International. Please provide an amended Competing Interests Statement that explicitly states this commercial funder, along with any other relevant declarations relating to employment, consultancy, patents, products in development, marketed products, etc.

Response: Thank you for highlighting this error. We have amended the submission.

5. We note that you have referenced (ie. Bewick et al. [5]) which has currently not yet been accepted for publication. Please remove this from your References and amend this to state in the body of your manuscript: (ie “Bewick et al. [Unpublished]”)

Response: Thank you for highlighting this. However, we did not cite Bewick et al.’s unpublished paper in our manuscript.

-------------------------------------------------------------------------------------------------------------------------------

Responses to Reviewers:

Reviewer #1:

Question 1:

The cost-benefits analysis (CBA) of implementing the proposed cost reimbursement scheme for child’s spectacle sounds great. However, the paper should talk about the hypothetical WTP cost for spectacles and the saving it will make for the individual, society or government provided that there is a multi-tier spectacle scheme system in place, where capable pay higher charges for the same spectacle as they stated willing to pay while poor pay small amount. The detail of the scheme is important to discuss stating how this works for both families and government.

Response: We thank the reviewer for the opportunity to clarify the perspective of the study as being that of the public payer and by extension the taxpayer.

Question 2:

Having just WTP findings cannot hypothetically estimate the benefits of the proposed spectacle reimbursement scheme. How much money family/government save can be stated by WTP results, but it does not the give the monetary value of benefits (impacts of having the scheme)? CBA is not only about knowing the cost but also measuring the benefit by that cost. The later part is not covered in the paper. My question is why do authors need to say CBA? Why not just say a WTP study and report the findings and discuss the potential benefits?

Response: We thank the reviewer for identifying a lack of clarity in our previous draft. As stated above the perspective of the study is that of the public payer and by extension the taxpayer over whose funds the payer has control. We accept that a range of benefits will flow from the scheme – benefits that extend beyond the improvements to visual acuity enjoyed directly by the individual whose refractive error is corrected and those which derive from this to include, for example, aspects of equity/solidarity. We have estimated the benefits to the taxpayer of the scheme using the study participant’s as representatives of the taxpayer. While we acknowledge this may give rise to risk of strategic bias – these are individuals whose children stand to benefit from the scheme - this must be counterbalanced by the risk of hypothetical bias associated with asking members of the public at large. We contend that the stated WTP provides an estimate of the present value of the discounted stream of benefits associated with the scheme expressed in monetary terms as perceived by taxpayers and as such can be compared with the schemes costs within a CBA. We have not sought to decompose or itemize the benefits but rather left this for the respondent to define in their own terms. We hope this clarifies this and have added additional text to the manuscript to provide further clarity and discuss the limitations of our approach.

Question 3:

If this is about the scheme to be launched by the government, it would be the compulsory service launched by the government in a public health system, which make richer pay high cost for the same product and poor pay less. If the parents would be willing to pay high amount of money for the spectacles, they would rather choose custom-made and high-quality spectacles that they can afford. Why would they need such scheme? The simple approach would be that the government can give the rebate if the annual income is low. Why to pay tax for the service or product which they may not require?

Response: The reviewer identifies an interesting alternative to the scheme (i.e. cross-subsidisation) posited to participants and valued by them. As it is a distinct scheme, we recommend that the potential of such scheme to be researched further.

Question 4:

Yet one another question, if authors found parents are willing to pay high, why 90% of children do not have spectacles for URE in Mongolia (reference 17) as stated in the introduction.

Response: We thank the reviewer for his/her question which again points to the need for greater clarity. That parents are willing to pay for their own child is not what we sought to value. Rather we sought to value how much taxpayers would be willing to pay for any child in need to have access to spectacles.

We presumed factors such as ignorance of refractive error and limited access to optometry services could all contribute to the estimate that 90% of children do not have access to spectacles.

Question 5:

Literatures also suggest that the ready-made spectacles are useful and beneficial to small number of populations. Majority would need custom-made spectacles. The use and importance of ready-made spectacles are mainly for the resource poor settings where the refraction services and custom-made options are not available, inaccessible or unaffordable. Is this the situation in Mongolia?

Response: Thank you for highlighting this, and indeed Mongolia has minimal capacity in providing optometry services. We included ready-made spectacles in the analysis to highlight its effectiveness in resource-limited settings. According to the International Agency for the Prevention of Blindness (IAPB) country human resource database, there is no optometrist workforce in Mongolia.[2] The already low number of ophthalmologists in public hospitals were also deployed to deliver refractive services and spectacles dispensing for the children - another reason to the high burden of uncorrected refractive error in Mongolia.

Question 6:

To highlight the benefits and implication/ significance of the scheme, the paper should explain about the proposed child’s spectacles reimbursement scheme? Who is proposing this scheme and what are the details of this scheme should be explained in the introduction?

Response: Thank you for highlighting this. As indicated above, our study focuses on cost-benefit analysis. The outcome of the findings can be used as an initial approach to propose to the government whether such a scheme is worth investing in reducing the burden of childhood vision impairment due to uncorrected refractive error in Mongolia. The designation of the reimbursement scheme will be our future work. We therefore added a description in the Introduction – “The Mongolian SHI is largely funded by the state central budget through general taxation. Should the proposed child’s spectacle reimbursement scheme be adopted by the government, the SHI would cover the reimbursement cost of eye examination and children’s spectacles. However, the actual framework for the reimbursement scheme is yet to be structured. The exploration of such a framework will be in our future scale-up study.”

Question 7:

The sample size is too low to look at the association with the factors mentioned in the paper. I recommend referring this as a pilot study and not describing as a cost benefit analysis as the endpoint beneficiary group is not clear based on the inclusion of study participants (taxpayers only).

Response: We thank the reviewer for this suggestion. On reflection we are inclined to agree with the reviewer and have highlighted in our limitations section that the results of this small study should be treated with caution and that a larger study should be undertaken to investigate further our findings.

Question 8:

As reported in strength of the current study in discussion - If additional taxes would have to be paid to subsidise free spectacles, why would these participants do so? They will/can purchase the spectacles straightforward rather than through the proposed scheme.

Response: We thank the reviewer for this question which we think arises from a misconception as to the role of the participant. Parents are being asked to value a scheme that benefits all children in need rather than just their own child. As noted, that is, the parent provides values as a taxpayer rather than a parent per se.

Question 9:

Design and setting section in methods state that WTP survey was used to estimate the benefits of providing spectacles to any children with RE. But the results only talk about cost of the product and WTP.

Response: We hope the comments provided already provide greater clarity on the approach adopted.

Question 10:

Sampling – target participants are taxpayers. Do you mean there are also people who do not pay tax because of low-income threshold? What is the income threshold level to whom this scheme is beneficial? If the problem is with those who cannot afford (who are not participants in the study), how this scheme would work is not clear?

Response: Hopefully our previous responses have clarified matters for the reviewer. To restate we sought to value the scheme from the public funder and by extension taxpayer’s perspective. As such a focus on the values of taxpayers seems entirely appropriate.

Question 11:

How was sample size of 50 participants determined? It is very low for any epidemiological or population-based study. This number is ideal for a pilot study before a main or large sample study. Why not say this a pilot study (state in title and objective)? What do you mean to sampling distribution was assumed to be normal?

Response: Thank you for raising this. We have addressed the question about sample size determination and sampling distribution in response to the academic editor’s comment above (kindly refer to Question 3). We acknowledge that 50 is a conservative number and therefore have amended in our title and objective that this is a pilot cost-benefit analysis. We edited the title, “A Pilot Cost-Benefit Analysis of a Children’s Spectacle Reimbursement Scheme: Evidence for Including Children’s Spectacles in Mongolia’s Social Health Insurance”; In the Introduction, “This pilot CBA is designed to assist eye health non-governmental organisation (NGO) Orbis International to provide initial findings to the Mongolian policymakers of the potential benefits of a proposed child’s spectacle reimbursement scheme.”

Question 12:

What is the basis for determining these bids figure $12.50, $17.50 or $22.50? It seems these were chosen to fit in the middle range of ready-made and custom-made spectacles. What proportions were ready to pay $12.50? What percentage were ready to pay $30? Why high- end of this bid is $30? It seems there are still high numbers of participants who would have been reporting that they are willing to pay high. Why not a last question was introduced to report the maximum amount they are willing to pay? It also sounds illogical to base on unpublished study.

Response: The bids were selected based on the cost of the spectacles and discussions with local eye care personnel as to their impressions of what might be reasonable. We agree a final open ended question would have been useful and would seek to incorporate that in further work.

The table below shows the proportion of final WTP by the surveyed respondents.

Final Willingness-to-pay

US$12.50

n US$15.00

n US$17.50

n US$20.00

n US$22.50

N US$25.00

n US$27.50

n US$30.00

n Total n

Starting Bid US$12.5 1 4 1 2 8 0 0 0 16

US$17.5 0 1 1 1 0 4 11 0 18

US$22.5 0 1 0 1 1 2 1 10 16

Total (%) 1 (2.0%) 6 (12%) 2 (4.0%) 4 (8.0%) 9 (18%) 6 (12%) 12 (24%) 10 (20%) 50 (100%)

Question 13:

Results/Discussion: The results are reported according to the methods mentioned. However, it should address the comments and questions raised above on the study methodology.

Response: Please see above our responses to the feedback.

Question 14:

There is a positive net benefit of $9 to whom? Government or parents? How is this beneficial to those who are willing to pay higher price than average custom-made spectacles cost? Yes, the beneficiary group would be the lower income threshold families, who are not part of the study? It would have been clear if family income was collected, and income was analysed as a factor to relate the association.

Response: From a public payer’s perspective – hopefully this is now clearer.

We agree that family income would be useful to help ascertain the face validity of the values generated, however, we did not include this as one of the demographic variables. We have therefore included this as a weakness in the Discussion.

-------------------------------------------------------------------------------------------------------------------------------

Reviewer #2:

Thank you for the opportunity to review this wonderful manuscript. This is well-constructed research with excellent writing. This study provides interesting new information to readers of PLOSONE and also to policymakers in Mongolia. I agree with authors on the strengths and acknowledge limitations of this study. Some specific comments noted below:

Question 1:

I am curious to see how the response will be if we explain the benefit of spectacles wear prior to questions about WTP since not everyone understands the importance of glasses.

Response: Thank you for the comment. We agreed that not all participants understand the benefit of spectacle wear, especially those without an uncorrected refractive error. However, we did not brief the participants about the benefit of spectacles wear prior to the WTP questions because rather than seek to itemise and describe the benefits which could intentionally influence the respondent, we chose to allow them to base responses on their own perceptions of benefits.

Question 2:

Any other explanation on why parents of children have refractive error WTP is less than parents of children have no refractive error. Is this possible that those parents who have children with refractive error have better idea about the cost of glasses?

Response: Thank you for the question. We explained in the Discussion - “Interestingly, in our study, respondents having children with refractive error had a lower WTP than respondents of children without. This may be because these parents’ have a different appreciation as to the benefit derived by children from the use of spectacles but we can only speculate as to what may underlie this result. It may relate to unobserved heterogeneity related to income, for example, those with RE having lower income in our sample. This should be examined in further research with a larger sample and where details of income are collected.”

Question 3:

About the potential predictors of WTP, can parent’s income be one of the confounding factor?

Response: Thank you for highlighting this. We agree that parent’s income is potentially a confounding factor that we were unable to address. We have therefore acknowledged this as one of the limitations in the Discussion and recommended to include this in the future study - “We only included variables such as parent’s age, sex, educational level, resident location, and children’s RE status in testing factors associated with WTP. The status of parent’s income could be a key indicator that should be included, as demonstrated by other studies which found to be significantly correlated with the final WTP.”

Question 4:

"90% of Mongolian children with VI due to URE do not have spectacles". That number is significant, and the study focuses mainly on the cost-benefit of glasses. Is there anything else lead to this number, can it be accessibility of eye care services or something else? I think if we can address and recommend in future study that would be great resource for policymakers.

Response: Thank you for the suggestion. We added a sentence in the Discussion – “The purpose of including children’s spectacles into Social Health Insurance is to allow children who had URE can access spectacles without facing financial hardship, thus reducing the burden of VI due to URE. While we found no studies exploring the barriers to the provision of spectacles in Mongolia, based on the available literature, we assume that the following factors were associated with the significant burden. Firstly, Mongolia has a limited workforce that can deliver paediatric eye examination and spectacles dispensing. Mountainous and upland steppe and semi-desert geography territories of Mongolia make children who live in rural unable to access eye health services and to procure spectacles in cities. Lastly, approximately one-third of the Mongolian population was living below the poverty line, where the cost of spectacles might be a financial burden for them. To inform policymakers and advocate a reimbursement scheme for children’s spectacles, we recommend exploration of those barriers should be included in the scale-up study.”

References

1. Mongolia Government. Mongolia National Program for Non-Communicable Diseases - The Government Resolution No.34 “Adoption of the National Programme". 289 Mongolia; 2017.

2. Number of Eye Care Personnel in Mongolia. [cited 5 Nov 2021]. Available: https://www.iapb.org/learn/vision-atlas/magnitude-and-projections/countries/mongolia

3. Kwak SG, Kim JH. Central limit theorem: the cornerstone of modern statistics. Korean J Anesth. 2017;70: 144–156.

Submitted filename: Response to Reviewers 20220117.docx

Click here for additional data file.

12 Apr 2022

Submitted filename: WTP Mongolia Reviewer comments.docx

Click here for additional data file.

3 May 2022

Reviewer #1:

It is good to read the revised manuscript with acknowledgement of the limitations on the generalisability of the results due to small sample size and no income threshold data to relate the validity of the findings. As indicated (with $19 benefit for RMS), the results suggest relatively high WTP of Mongolians despite 90% RE children (relating half suitable for ready-made) being possibly uncorrected. In addition to this, those with RE are more likely to pay less than those without, is certainly question of investigation. As concluded, the full-scale study with greater sample size and proper selection of participants, will hopefully contribute to purposing the structure of reimbursement for spectacle.

1. Unlike this study (spectacle reimbursement scheme), previous WTP studies contribute/suggest for “spectacle cost-subsidisation scheme”. You may discuss the difference and highlight the SMI features and focus. Importantly, is this meant for RMS, custom-made or both? The question and response are dependent to the specific product and accordingly relate the scheme. Ideally, WTP question is to base on the focus or the need; for ready-made or custom-made. If relevant and useful, add to highlight.

Response: Thank you for suggesting this. We added this into our Discussions: “The observation of Cambodian respondents in offering lower WTP can be explained by the following reasons. Firstly, the proposed scheme in Mongolia was to include spectacle provision through the Social Health Insurance which will not incur any payment at the service points, while in Cambodia, the proposed cross-subsidisation scheme will require parents to pay a nominal amount. Secondly, the difference may be due to a higher gross domestic product per capita in Mongolia than Cambodia (US$4,339 versus US$1,643).[35,36] Lastly, our study uses additional annual taxes as the payment vehicle, while in Cambodia, the payment was through out-of-pocket expenses.”

We recognised the limitation of not specifying which types of spectacles (ready-made or custom-made) that the tax payer would be willing to pay. However, we chose to use mix spectacles (US$15) as the spectacle cost because i) one in two Mongolian children who had refractive error can be corrected effectively from a pair of inexpensive, ready-made spectacles, and ii) to reflect the practical situation where there will be need to have a combination of both ready-made and custom-made spectacles to cover the refractive needs of the children. “Based on a dataset obtained from an outreach vision screening programme initiated by an international eye NGO, one in two Mongolian children who had refractive error can be corrected effectively from a pair of inexpensive, ready-made spectacles. Therefore, the costs of ready-made spectacles and custom spectacles were used to construct the cost of a mixed offering to reflect the need for a combination of both spectacle types to address the refractive needs of the children.” We included this content in the Methods section.

We also highlighted the following in the Limitations “In addition, employing the costs of ready-made spectacles and custom spectacles to construct the cost of a mixed offering may have also confounded the results, but we felt it was necessary to reflect the local refractive needs.”

2. Discussion third paragraph - Unlike this study, reference no 34 do not have a compare group. The Cambodia study included only parents of children with RE. Please correct ‘an eye disorder’ with ‘refractive error’. About 53% parents were willing to pay $17.50 (standard price of custom-made spectacle) or more.

Response: Thank you for spotting this error. We have amended the sentence accordingly.

3. Reason for “Those with RE had low WTP compared to without” is simply unanswerable in given situation. The listed potential reasons (different appreciation and income) do not quite relate or suit. I suggest delete and simply indicate the need for clarification /verification through full-scale study.

Response: Thank you for highlighting this. We agreed that findings of “those with RE had low WTP compared to without” is unanswerable. We also agreed that there is a need for clarification/verification through full-scale study, as added to the Discussion “This should be examined in further research with a larger sample and where details of income are collected”.

4. In the concluding statements, it is better to state clearly about the scheme that it is the proposed or potential spectacle reimbursement scheme under SMI.

Response: Thank you for highlighting this. In the conclusion, we made clear statement that, “Our preliminary findings suggest that there is potential to include children’s spectacles into the existing Social Health Insurance. However, further research with larger sample size is needed to confirm this.”

Reviewer #2: (No Response)

Submitted filename: Response to Reviewers_CBA Mongolia_20220502.docx

Click here for additional data file.

2 Aug 2022

A Pilot Cost-Benefit Analysis of a Children’s Spectacle Reimbursement Scheme: Evidence for Including Children’s Spectacles in Mongolia’s Social Health Insurance

PONE-D-21-24356R2

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Reviewer #1: (No Response)

Reviewer #2: It will be beneficial for the next study to use Visual Analog Scale to evaluate WTP. Looks like from the WTP of both rural and urban people is close to custom lenses price so maybe other factor like accessibility to eye care is bigger issue. Also the cost of ready made and custom made glasses might be lowered when the this scheme is adapted to the government coverage since they will have better buying power to negotiate better price.

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Reviewer #1: Yes: Prakash Paudel

Reviewer #2: No

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5 Aug 2022

PONE-D-21-24356R2

A Pilot Cost-Benefit Analysis of a Children’s Spectacle Reimbursement Scheme: Evidence for Including Children’s Spectacles in Mongolia’s Social Health Insurance

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