Geographic access to optometry services across Canada: Mapping distribution, need and self-reported use


 Background This research investigates the distribution of optometrists in Canada relative to population health needs and self-reported use of vision care services with a focus on identifying variation and poorly served health regions in order to gain a clearer understanding of geographic proximity of optometry services.Methods Optometrist locations were gathered from resources provided by provincial regulatory bodies. A geocoding approach then converted these descriptive data into a set of geographic coordinates. Utilization of vision care services was extracted from the Canadian Community Health Survey (CCHS) 2013-2014 question regarding self-reported contacts with vision care providers. Data from the 2016 Statistics Canada census were used to create three population ‘need’ subgroups (65 years and over; low-income; and people aged 15 and over with less than a high school diploma). Optometrist-to-population ratios, expressed as number of providers per 10,000 people at the health region level, were then calculated. Cross-classification mapping compared optometrist distribution to self-reported use of vision care services in relation to need. Results A total of 5,959 optometrists working across ten Canadian provinces were included in this analysis. The nationwide distribution of optometrists is variable across Canada and they are predominantly concentrated in densely populated urban areas. The mean ratio of optometrists across Canada was 1.70 optometrists per 10,000 people (range = 0.13 to 2.92). Out of 109 health regions (HRs), 26 were classified as low ratios, 51 HRs were classified as moderate ratios, and 32 HRs were high ratios. Thirty-five HRs were classified as low utilization, 39 HRs were classified as moderate, and 32 HRs as high utilization. HRs with a low optometrist ratio relative to eye care utilization and a high proportion of key sociodemographic characteristics are located throughout Canada and identified with maps indicating areas of likely greater need for optometry services. Conclusion This research provides a nationwide overview of vision care provided by optometrists identifying gaps in geographic access relative to “supply” and “need” factors. This in-depth examination of variation in population accessibility to optometric services will be useful to inform workforce planning and policies at national, provincial, and health region levels.

Conclusion This research provides a nationwide overview of vision care provided by optometrists identifying gaps in geographic access relative to "supply" and "need" factors. This in-depth examination of variation in population accessibility to optometric services will be useful to inform workforce planning and policies at national, provincial, and health region levels.

Background
Primary health care (PHC) in Canada includes a variety of services from a range of health professionals providing comprehensive care and coordination with other levels of care.
Access to PHC services is a considerable health delivery concern across Canada with important health policy implications. Some communities, particularly in rural and remote areas, do not have the same access to a range of primary health care professionals. Such differences in access to health services have negative consequences for best meeting population health needs. Geographic access to PHC services involves investigating the distribution of these services in relation to population health needs. [1][2][3] The increasing interest in geographic access to PHC services in Canada has focused predominantly on physicians, and dentists. [4][5][6][7][8][9][10] In relation to vision care services, the few studies in Canada to date have focused on either ophthalmologists only [11,12] or combined distribution of ophthalmologists and optometrists. [13] Optometrists are identified as "independent primary health care providers and represent the front line of vision health" (CAO website) and practice in a diverse range of settings across Canada including private practice, community health centres, and hospitals. Research investigating vision care provider use (i.e. optometrist or ophthalmologist) based on a self-reported national survey in Canada, found that populations having high risk of vision loss may lack access to eye care services [14], socioeconomic characteristics may be barriers to eye service utilization among certain subgroups [15], and those without additional health insurance have reduced use and access to eye care services. [16] However, having additional health care insurance does not necessarily result in equitable access to eye care services. Residents of countries with low densities of eye care professionals, for example, have reduced likelihood of vision service access, even among those with insurance. [17] Further, rural and remote residents face additional challenges due to longer travel distances to receive vision care. [18] To date, there has been little work in Canada that has focused solely on investigating the distribution of optometry services relative to potential need and use. The aim of this research was to explore the distribution of optometrists in relation to population health needs and self-reported use of vision care services across Canada in order to identify potential gaps in geographic access relative to "supply" of and "need" for such factors.
Specifically, this research: 1) identifies variation and poorly-served areas (i.e. health regions) to optometry services across Canada; 2) analyzes and maps the self-reported use of vision care services in relation to optometrist distribution; and 3) maps the patterns of spatial distribution of optometrists in relation to census-based socio-demographic characteristics (e.g. age, income, education).

Methods
This research is based on the number of optometrists per population (i.e. optometrist distribution ratio), eye services utilization (including optometrists and ophthalmologists), and population subgroups that may have higher health care needs (i.e. seniors population, low-income measures, and less education) (see Figure 1). The primary practice locations of optometrists in Canada were gathered from the provincial regulatory bodies. The Canadian Association of Optometrists (CAO) gathered primary practice information of optometrists for 2017 (i.e. six-digit postal codes) from seven provinces (British Columbia, Manitoba, New Brunswick, Ontario, Prince Edward Island, Quebec, Saskatchewan) whereas data from the remaining three provinces (i.e. Alberta, Newfoundland and Labrador, Nova Scotia) was downloaded directly from each of the provincial regulatory college's website.
CAO was unable to provide optometrist information for three Territories due to unavailability of any licensing bodies to provide data. A set of geographic coordinates for primary practice locations were generated using postal code geocoding and Google Maps.
Next, in order to aggregate data in various geographic scales, supporting attributes from other layers such as health region boundaries, census subdivision (CSD) geographic units were assigned to each location. Ontario Data Documentation, Extraction Service and Infrastructure (odesi) web-based data exploration, extraction, and analysis tool (https://odesi.ca/). The CCHS is a cross-sectional, nationwide, and self-reported household survey that was collected from persons aged 12 and over living in Canadian health regions except those living on a reserve or as fulltime member of the Canadian Forces. We used the following question to derive the information about utilization of eye care services at health regions: "CHP_Q06: [Not counting when you were an overnight patient, in the past 12 months/In the past 12 months], have you seen, or talked to: an eye specialist, such as an ophthalmologist or optometrist (about your physical, emotional or mental health)?" Unfortunately, the wording of the CHP question related to vision care services does not distinguish between optometrist or ophthalmologist use. Comparative analyses of ratio and utilization variables in association with population subgroups that usually have much higher health care needs was performed. We focused on the following three population subgroups with potentially higher needs: seniors (age 65 years and over), low-income, and lower educational attainment. Information about these three variables were extracted from 2016 Census and downloaded from the Statistics Canada website. The 2016 dissemination area (DA) census data were used to prepare the following HR level variables: population 65 years and over, low-income measures, and the population aged 15 and over with less than a high school diploma. These variables were expressed as percentages.
Geospatial mapping methods that were used to analyze the patterns of optometrists per 10,000 population (i.e. ratio), self-reported eye care services utilization, and population subgroups can be divided into three ways. First, optometrist practice locations were associated with the different urban-rural classifications where we used statistical area classification to categorize census subdivisions (municipalities) into metropolitan and metropolitan influence zones (MIZs). [19] The MIZ classifies the CSDs outside census metropolitan areas (CMAs) and census agglomerations (CA) into "four categories according to the degree of influence (strong, moderate, weak, or no influence) that the CMAs or CAs have on them." [19] Second, optometrist ratios estimated at health regions levels were mapped. This was done after converting ratio values into five categories where a standard deviation (SD) classification approach was used (± 0.5 SD from the mean value were used as a cut-off for demonstrating distribution of optometrists across health regions). Third, a cross-classification technique was utilized to map the patterns of spatial distribution of optometrists in relation to self-reported use of vision care services and population subgroups. This was performed after separating optometrist ratio and selfreported utilization of eye services into three classes, based on a standard deviation classification scheme, as follows: low, moderate, and high. Similarly, the patterns of spatial distribution of optometrists in relation to census-based socio-demographic characteristics (i.e., seniors' population, low-income measures, and lower educational attainment) were mapped. A similar classification scheme was applied for converting the percent of these population subgroups into three classes: low (< -1.5 SD; -1.5 to -0.50 SD), moderate (-0.5 to 0.5 SD), and high (0.50 to 1.5 SD, > 1.5 SD).
The following software were used for mapping and data analysis (spatial and nonspatial):

Results
This analysis is based on 5,959 optometrists working across Canada. As shown in Table 1, we generated geographic locations using the following geocoding methods: postal code geocoding (n = 5,835; 97.9%), and Google Maps (n = 114; 1.9%). There were 10 optometrists (0.17%) where address information was not provided, and these were excluded from the analysis. Optometrist ratios were mapped after converting into a categorical variable by following a standard deviation (SD) scheme where a ± 0.5 SD from the mean value was used as a cutoff for demonstrating distribution of optometrists across health regions. The first two categories (< -1.5 SD; -1.5 to -0.50 SD) indicate poor distribution of optometrists (i.e., lower category), the third category (-0.5 to 0.5 SD) moderate, and the last two (0.5 to 1.5 SD, > 1.5 SD) indicate higher geographical availability of optometry services. Regarding optometrist ratio per 10,000 people: out of 109 HRs, 26 were in the lower categories, 51 HRs in the moderate, and 32 HRs in the higher categories as seen in the sum of values given in the legend of Figure 3. Table 1 presents the province wide distribution of the total population (and HR counts) across the optometrist ratio categories (5-classes based on the standard deviation approach). About 9.2% of total population (i.e., 3.24 million) in 26 HRs from eight provinces (i.e. all except NS and PE) fall under the lower categories of optometrists per population ratios (i.e., < -1.5 SD; -1.5 SD to -0.50 SD).
Optometrist distribution patterns relative to utilization of eye care services demonstrates moderate-low optometrist availability in health regions with moderate-high utilization of eye care services ( Figure 4) and in health regions with relatively higher percentage of population subgroups (higher than the national average) (Figures 5-7). Cross-classification between the ratio and use variables where 106 HRs were divided into nine category combinations ( Figure 4). Health regions with low optometrist ratio values relative to the low utilization of eye care are located throughout Canada. There are nine HRs (8.5%) that fell within the high utilization-high distribution ratio combination (1 HR from each of NB, QC, and SK, 6 from ON). Ten HRs (9.4%) from the following provinces were found to have a low utilization-low distribution ratio combination: 1 HR from each of NB, ON, and AB, 2 from each of BC, and NL, 3 from MB. Ten HRs (9.4%) fell within high utilization-low distribution ratio combination: 1 HR from each of NB, and AB, 2 from ON, 3 from SK). Eight HRs (7.5%) had a low utilization-high distribution ratio combination: 1 HR from ON, 3 from BC, and 4 from QC. Various other combinations with moderate utilization or distribution were found in 69 HRs distributed across all 10 provinces.
Cross-classification between the ratios and socio-demographic characteristics (3 variables) were divided into nine category combinations are shown in Figure 5    Ensuring adequate geographical distribution of health human resources and services is a key component of ensuring equitable access to health care. [25] Realized access is actual use of services, whereas potential access is linked to an individual's perception of access as well as other contextual and environmental factors, such as geographical distribution of services. [26] Our findings point out uneven distribution of optometrists relative to utilization and key socio-demographic indicators across Canadian health regions, suggesting that there are potential gaps in equitable access to care. It is important to note that optometrist-use data do not directly relate to population health need because those who need the service may not necessarily be able to access care for a variety of reasons. Access and use are not synonymous because an individual may need to overcome barriers that limit her or his access to a particular service in order to use it. [27] Furthermore, the health care needs of an individual do not necessarily reflect access to particular services, nor do health care needs consistently correlate with patterns of health care use. [28] Limitations and other considerations   Cross-classification map of optometrist per 10,000 population (Ratio) with lowincome families; Labels: L=low; M=moderate; H=high