Global Mapping of Optometry Workforce

Abstract


Background
Skilled and motivated health workers in su cient numbers located appropriately in places with unmet needs are critical to deliver effective health services and improve health outcomes.[1] The World Report on Vision highlighted the need for an increase in eye health human resources to address the enormous magnitude of vision and eye health problems [2] -at least 2.2 billion people globally have a vision impairment, of which about 1 billion is preventable or yet to be addressed.[2] While budgets de ne the ability of countries to provide resources, even with enough nances, the paucity of relevant and appropriately trained human resources, especially optometrists and ophthalmologists, [3] are still a barrier to equitable access to quality eye care.Hence, 90% of the burden caused by vision impairment is found in developing countries.
Holden et al. [4] estimated that 2.6 billion people were living with myopia, while Frick et al. [5] reported 1.8 billion people living with presbyopia.Holden et al. [4] also established the alarming projection of 5 billion people living with myopia by 2050.This looming crisis will not only add to the number of people with uncorrected refractive error (URE) but also the number of people with other potentially blinding conditions such as glaucoma, retinal detachment and cataracts.Furthermore, conditions such as diabetic retinopathy, age-related macular degeneration and ailments arising from evolving visually demanding lifestyles (dry eye and binocularity problems) will increase the need for vision care and further amplify a global burden, which already exceeds the human resources for eye health currently available worldwide.
An optometrist, whose core function is detecting, measuring and correcting refractive error, and detecting and managing primary eye care and other conditions of public health concern that add to the global burden of vision impairment, is best placed to contribute to the disease control strategy.The World Council of Optometry de nes an optometrist as a healthcare profession that is autonomous, educated, and regulated (licensed or registered).Optometrists are the primary healthcare practitioners of the eye and visual system who provide comprehensive eye and vision care, which includes refraction and dispensing, detection/diagnosis and management of eye disease, and visual system rehabilitation.[6]The importance of optometry was highlighted as an essential workforce in the Universal Eye Health: A Global Action Plan 2014-2019.[7] However, the insu cient number of optometrists means limited screening and reduced accessibility to refractiveservices and optical correction.This has contributed to a large number vision impairment due to URE, a condition that can be safely and inexpensively corrected, yet has become the primary cause of vision impairment.[8] There have been attempts to quantify the global number of optometrists previously, but they did not provide a robust estimate, partly because these results were generated from a few countries where optometry is well-de ned and regulated.The World Council of Optometry, which represents a large proportion of optometrists globally, suggests that it represents 200,000 optometrists from 89 member organisations in over 48 countries.[9] Fricke et al. [10] estimated the number of "functional clinical refractionists" (person who spends 100% of clinical time providing refraction services) to be 167,013 -a gure that is probably biased towards optometrists.The gross estimate of 300,000 optometrists is often used as the existing number of optometrists globally, but this estimate is not based on a formal evaluation.The estimate is further affected by the varying de nitions of the profession of optometry that are used across countries.
The result is an inaccurate estimate of an "optometry pool" of eye care workers of varying educational backgrounds providing refraction and/or refractive services at different levels of care and competency.This raises the following questions: i) how many optometry personnel are there globally?ii) where are they distributed, and iii) at what level of competency are they practising?Unless these questions are answered, developing adequate strategies to overcome this burden will be di cult to achieve.
The primary objectives of this study were to determine the ratio of optometrists to the population according to Global Burden of Disease Regions and its association to the gross domestic product (GDP) per capita and prevalence of blindness and moderate and severe vision impairment.We also investigated the number of training institutes and optometry graduates in the countries.We hypothesised that in countries with a lower number of optometry workforces, the prevalence of blindness and vision impairment would be higher than in countries where the number of optometry workforces is meeting the recommended practitioner-to-population ratio.

Methodology
A cross-sectional study utilising quantitative methods was conducted from February 2017 to May 2020.Non-random, purposive sampling and a key informant strategy was employed.The key informants were linked to either the World Council of Optometry members, other ophthalmic groups, prominent academics or individuals playing a key role in eye health development.These individuals were invited to complete the survey, which focussed on ascertaining the quantity and distribution of optometrists globally.When necessary, clari cation on the survey questions was provided via direct communication, either verbally or via digital communications.A standardised English language questionnaire was designed to obtain the key indicators needed.Concerted efforts were made to reach those countries that initially did not respond.If the original key informant could not respond to the survey, they were asked for referrals to other individuals who could provide the necessary information.
The original English language survey was translated into Spanish, French, and Mandarin for ease of completion for those whose primary language was not English and were not comfortable responding to an English survey.Translators were used to translate the responses to English if they were self-administered in languages other than English.The survey was distributed via an email link (online survey) or on paper or Microsoft O ce Word format for internet-limited settings.Respondents provided consent to participate in the survey before answering the speci c research questions.
According to the Institute for Health Metric and Evaluation (IHME), there were 200 Global Burden of Disease countries (http://ghdx.healthdata.org/countries).
However, 152 countries were included in the survey, with 48 countries being excluded due to unobtainable key informants as optometry does not formally exist in all countries.Data collected was reviewed, missing data were identi ed, and key informants were approached to provide the missing data or clari cation, where possible.
The main questions presented to respondents were as follows (see Appendix 1 for further details): 1. What was the source of the information provided?2. What was the number of professionals functioning at the various WCO Competency levels?3. How many Optometry training institutions were there in the country?4. How many optometrists did the optometry training institutions graduate per annum? 5. Was Optometry regulated?
The WCO Competency Model was used to de ne optometry with four categories of services which were: 1. Category 1: Optical Technology Services: Management and dispensing of ophthalmic lenses, ophthalmic frames and other ophthalmic devices that correct defects of the visual system 2. Category 2: Visual Function Services: Investigation, examination, measurement, diagnosis and correction/management of defects of the visual system 3. Category 3: Ocular Diagnostic Services: Investigation, examination and evaluation of the eye and adnexa and associated systemic factors to detect, diagnose and manage the disease 4. Category 4: Ocular Therapeutic Services: Use of pharmaceutical agents and other procedures to manage ocular conditions/disease Based on this optometry workforce scope of practice, practitioners practising at Category 2 and above were considered to be de ned as Optometrists.Our analysis excluded practitioners functioning at Category 1, who are based solely on dispensing spectacles, without investigation, examination, measurement, diagnosis and correction or management of the visual system defects.
Data was captured in a Microsoft Excel spreadsheet and then exported to Statistical Package for the Social Sciences (SPSS v26.0) for data cleaning and subsequent analysis.Descriptive statistics in the forms of frequencies and distributions were used to assess the response rates across 21 GBD regions, key informant's background and the source of information, country's capacity in training optometrists, regulation and continuous medical education in the respective country.The number of optometrists and the total population in the country were used to calculate the optometrist-to-population ratios, regionally and by country.Spearman's correlation analysis was used to test the association between the optometrist-to-population ratio and the demographic variables such as country's GDP per capita, the age-standardised prevalence of blindness and moderate and severe vision impairment (MSVI), with the signi cance level set at 5%.Ethics approval was obtained from the Human and Social Sciences Research Ethics Committee (Reference number: HSS/2135/016) from the University of KwaZulu-Natal, Durban, South Africa.

Survey response rate
We received responses from 123 of the 152 countries invited for the survey, resulting in an overall response rate of 80.9%.Forty-eight of the 200 GBD countries were excluded due to unobtainable key informants.Table 1 shows the distribution of responses of countries by GBD region.Regions with lower response rates were mainly from Sub-Saharan Africa, with the Central region being the lowest with 50.0%, followed by Western and Southern regions with 63.2% and 66.7%, respectively.Relationship between the optometrist-to-population ratio and the country demographic characteristics A higher age-standardised prevalence of blindness was signi cantly associated with a lower optometrist-to-population ratio at the country level (p<0.001,r=0.721) (Figure 1).This correlation was considered strong as the r-value was more than 0.7.A similar nding was reported for the age-standardised prevalence of mild and severe vision impairment, where a signi cant moderate direct positive relationship between the burden of disease and the optometristto-population ratio was observed (p<0.001,r=0.636) (Figure 2).
A signi cant inverse relationship was observed between the country gross domestic product per capita and the optometrist-to-population ratio (p<0.001,r=-0.770)(Figure 3).Lower country gross domestic product per capita is correlated with a greater de cit of optometrists in the country.

Country's capacity in training optometrist
A total of 19,265 optometrists graduate from 123 countries annually (Table 4).Western Europe trained the highest number of optometrists among the 21 GBD regions (4,594 graduates), followed by South Asia (4,492 graduates), High-income Asia Paci c (2,160 graduates) and East Asia (2,100 graduates).Three regions did not have institutions within the countries to train optometrists, speci cally, Central Asia, Central Sub-Saharan Africa, ad Oceania.

Country's regulation on optometry and continuous medical education
Out of the 123 countries, less than half of the surveyed countries (n=54, 43.9%) regulated optometry as an eye care professional.(Table 4) Optometry was recognised in all the countries in Australasia, high-income Asia Paci c and High-income North America regions.Forty-two countries (34.1%) imposed mandatory continuing professional education to maintain optometrists' competency level and further equip them with up-to-date practices.

Discussion
Our study quanti ed the number of optometrists functioning according to the WCO competency level.The optometrist-to-population ratio globally of one optometrist to 20,479 persons appears reasonable when viewed in the developing world context (1:50,000 recommended ratio) [11].However, this ratio masks the unequal distribution of the workforce across countries or regions.Central Sub-Saharan Africa, for example, is serving 1,198,141 populations, compared to 3,877 populations in Western Europe.Approximately half of the countries (53.7%) met the 1: 50,000 ratio, with all high-income regions meeting the 1: 10,000 ratio.
Anecdotal evidence suggests that the ratio of optometrists to population is critically low in rural and outlying areas and magni es the de cits displayed in our data.This paucity of optometrists in the developing world is further accentuated when one considers intra-country variations whereby optometrists, like most eye care providers are con ned to the major cities.While producing more optometrists is imperative to address the unequal distribution, the workforce must be more effectively distributed, a major challenge given the lack of incentives [13] and facilities in rural and remote areas, making recruitment di cult.
Developing an adequate number for the workforce is a complex task due to numerous factors, including key elements such as the lack of educators, the length of training for professionals, regulatory barriers, and the cost of setting up training institutions.However, Thompson et al. showed that implementing an optometry program de novo in a developing country is cost-effective, [14] which in the best case scenario reaches self-su ciency in 10-12 years post setup, using conservative approaches and restricted means.A lower country GDP per capita is correlated with a greater shortage of optometrists in countries.As such, resources may not always be available for the establishment of schools of optometry.Strong advocacy supported by a robust evidence base such as the impact of poor vision on productivity [15][16][17] or learning [18][19][20], which is documented, is needed to make a case for the value of optometry school development.International collaboration needs to be mobilised to ensure that academic, logistical and material support is provided for new schools, and new policy formulation needs to overcome regulatory barriers.However, the current status in the low-income countries indicates that the de cits seen in the number of optometrists will not be addressed soon.As few new optometrists are being trained, innovative strategies that encompass the following need ot be explored: Team approach: While vision screening is done at a primary level by allied health professionals, linking optometrists in the referral pathway is imperative to ensure a continuum of care.Optical assistants/technicians assisting in refractive services by doing some preliminary testing can help increase the effectiveness of optometrists.Similarly, the referral pathway for available optometrists to ophthalmologists and other specialty services for a higher level of care needs to be facilitated.In adopting a team approach, optometrists can provide the care needed by three types of patients: those who need ongoing care, those at early-stage disease and those with symptomatic conditions without vision impairment but still need services.[21] Technology: Strategies such as using more cost-effective tools to increase the quality of care and increase the output of optometrists needs to be explored.Furthermore, the optometry workforce needs to be mobilised to reach outlying rural areas via outreach activity or supporting social businesses in under-developed areas.Tele-health overseen by optometry may support distance monitoring and oversight to potentially provide a greater reach for the profession.These strategies, however, need to be carefully developed without compromising the quality of care.
Upskilling: In countries where optometry is not developed, post-graduate and continuing professional education must be explored to expand the knowledge and skills of existing cadres so that they can be integrated into the optometry profession.This takes on increasing importance in an era where other morbidities such as diabetic retinopathy and glaucoma are becoming a signi cant threat to visual health if detection and treatment are delayed.
The World Report on Vision states that at least 1 billion people in the world with vision impairment could have been prevented or have yet to be addressed.[2] Of this, almost 950 million is related to refractive error and presbyopia; both are key responsibilities of optometrists to address.The correlation between low numbers of optometrists and a high prevalence of vision impairment and blindness in regions thus indicates that unless urgent action is taken to increase the number of optometrists trained and deployed to underserved areas in low-income countries, plans to eliminate preventable vision impairment will remain elusive.In addition, implementing comprehensive eye care will be di cult to provide as this requires a team, with the optometrists as a critical component of that team.
Although optometrists were trained and competent in delivering primary eye care to the populations, more than half of the surveyed countries did not o cially regulate this profession as part of the health system.This implies that advocacy work must be undertaken to make optometry visible to the governing bodies, the relevant authorities, and the public.The recognition of the profession is vital to enable funding priority in training an adequate number for the optometry workforce to support the population's needs in eye health services.
While this study had a good response rate, one limitation was the inability to reach all countries where optometry is practised, or where optometric care is delivered under a different technical terminology.There is a need to expand this data collection to all of the 200 GBD countries.However, the data identi es the divide between the low-income and high-income regions and countries in the training and deployment of optometrists.A follow-up study will be conducted to ensure that more countries are included.

Conclusion
Our study found that high-income countries met the target for optometrist-to-patient ratios.Low-to-middle-income countries and low-income countries did not only fail to meet the targets, but they are also far from reaching them.The low optometrist-to-patient ratios are strongly associated with a higher magnitude of blindness and vision impairment.
The number of optometrists worldwide is increasing, but gaps remain in numerous areas around the world.Unless these gaps are addressed, we will not make a signi cant contribution towards achieving targets related to Universal Health Coverage and the Sustainable Development Goals outlined by the United Nations.According to the World Report on Vision, "Everyone, if they live long enough, will experience at least one eye condition in their lifetime.For example, many people will have had conjunctivitis as a child, will need spectacles due to presbyopia sometime after 40 years of age, or require cataract surgery later in life."This statement ampli es the need for eye care globally.With the lack of optometrists in the low-income areas of the world, optometry training and output will have to be signi cantly accelerated or upscaled to address the increased demand for eye care.The relationship between the optometrist-to-population ratio and the age-standardised prevalence of blindness The relationship between the optometrist-to-population ratio and the age-standardised prevalence of mild and severe vision impairment

Figures Figure 1
Figures

Table 1
Total number of countries included in the survey and the response rates (n=152 countries) *Source: Institute for Health Metric and Evaluation (IHME) list of Global Burden of Disease countries (http://ghdx.healthdata.org/countries).Refer to Online Supplementary File 1 for the list of countries.Key informant's background and source of informationMost respondents were a liated with universities or research institutes (53 countries, 43.1%) or professional associations (42 countries, 34.1%) (Table2).Most key informants were academics (40.7%), followed by association representatives (30.9%).More than half of the respondents' information (55.3%) was from government sources, primarily the Ministry of Health, Health Council Registry, and Medical Council Registry.

Table 2 A
liations, key informants and source of information (n=123 responded countries) [11]uided by the World Council of Optometry, practitioners practising at Category 2 to 4 were considered to be optometrists.The reported number of optometrists across 21 GBD regions was 331,781 as of the year 2019, covering 88.5% of the global population (6.79 billion in 123 countries) (Table3).The number of Category 4 optometrists were three times less than those practising at Category 2 (55,427 and 169,076, respectively).Seven regions reported no optometrists practising at Category 4 referring to Andean Latin America, Southern Latin America, Tropical Latin America, Central Asia, Central and Eastern Europe, and High-income Asia Paci c.Considering the optometrist-to-opulation ratio, globally, one optometrist is serving an average of 20,479 persons.The unequal workforce distribution across countries and regions showed that in Central Sub-Saharan Africa, one optometrist serves 1,198,141 persons, compared to 3,877 populations in Western Europe.Among the 123 countries, 66 (53.7%) met the World Health Organisation recommended 1 optometrist to 50,000 persons target (1: 50,000),[11]while

Table 3
The number of optometrists and the ratio of optometrists to the population according to Global Burden of Disease regions **Refer to Online Supplementary File 2 for details at the country level.
*Source: United Nation World Population Prospect 2019 (https://population.un.org/wpp/Download/Standard/Population/) ** There was no optometrist in the Central Asia region.***Refer to Online Supplementary File 2 for details at the country level.*

Table 4
The number of training institutions, graduates per annum, countries with regulation and continuing medical education according to Global Burden of Disease Regions