The Impact of Lack of Government-Insured Routine Eye Examinations on the Incidence of Self-Reported Glaucoma, Cataracts, and Vision Loss

Abstract

Purpose.: We determined the impact of lack of government insured routine eye examinations on the incidence of self-reported glaucoma, cataracts and vision loss.

Methods.: We analyzed data from the Canadian longitudinal National Population Health Survey (1994–2011). White respondents aged 65+ in 1994/1995 were included (n = 2618). Three cohorts were established at baseline: those free of glaucoma, cataracts, and vision loss (i.e., unable to see close or distance when wearing glasses or contact lenses). Incident cases were identified through self-reporting of these conditions during the follow-up period.

Results.: The incidence (per 1000 person-years) of glaucoma was lower in uninsured provinces (8.1; 95% confidence interval [CI], 5.5–10.7) than in insured provinces (12.8; 95% CI, 10.5–15.1). The incidence of cataracts was also lower in the uninsured (67.2; 95% CI, 55.7–78.6) versus insured provinces (75.7; 95% CI, 69.2–82.2). The incidence of vision loss was higher in the uninsured (26.6; 95% CI, 20.2–33.0) versus insured provinces (22.5; 95% CI, 20.0–25.5). Adjusting for confounders, seniors in insured provinces had a 59% increased risk of glaucoma (incidence rate ratio [IRR], 1.59; 95% CI, 1.07–2.37), a 13% greater risk of cataracts (IRR, 1.13; 95% CI, 0.93–1.37), and a 12% reduced risk of vision loss (IRR, 0.88; 95% CI, 0.67–1.16).

Conclusions.: Lack of government-funded routine eye examinations is associated with a reduced incidence of self-reported glaucoma and cataracts, likely due to reduced detection. Lack of insurance also is associated with a higher incidence of self-reported vision loss, likely due to poorer access to eye care and late treatment.

Introduction

Reduced vision can adversely impact quality of life and is associated with disability, decreased participation in social and leisure activities, depression, and fractures from falls in older adults.^1–6 Many sight-threatening conditions, such as glaucoma and diabetic retinopathy, are asymptomatic in the early stages, and a general or routine eye examination is required for timely diagnosis of these treatable potentially blinding conditions before irreversible vision loss occurs. 

Although treatment for diagnosed eye diseases, such as glaucoma, cataracts, and diabetic retinopathy, is universally covered in Canada, eye care services for routine eye examinations are unevenly funded by provincial governments across the country. As a result, access to routine eye examinations in Canada depends on location of residence, age, and willingness or ability to pay.⁷ Previous research using cross-sectional data has shown that eye care use is lower in areas of Canada where routine eye examinations are not insured.^8,9 The prevalence of self-reported vision loss also is higher among poor Canadians residing in these provinces.¹⁰ Studies from the United States have shown that lack of insurance coverage is associated with lower use of eye care services and higher rates of undetected eye disease.^11–15 

Due to the cross-sectional nature of the data reported in previous studies, a causal relationship between lack of government-funded routine eye examinations and vision loss has not been established. The Canadian longitudinal National Population Health Survey (NPHS) provides an opportunity to further investigate this issue. Using the NPHS data, we aimed to assess the impact of living in provinces without government funded routine eye examinations on the incidence rates of three vision conditions: glaucoma, cataracts, and vision loss. 

Methods

Data Source

The NPHS was a longitudinal, self-reported health survey conducted by Statistics Canada. The first cycle of data collection was started in 1994/1995, with follow-up cycles every two years, ending with the ninth cycle in 2010/2011. A two-stage sampling strategy was used to select respondents aged 0 years or older at baseline (n = 17,276) that were representative of the Canadian population.¹⁶ No additional respondents were enrolled in follow-up cycles. Computer-assisted interviews were conducted over the phone or in person to collect information. Deaths reported in the survey were confirmed using the Canadian Vital Statistics Database. Response rate in the first cycle was 86.0%, and ranged between 69.7% and 92.8% in subsequent cycles. Data were accessed through the Statistics Canada Research Data Center in Toronto, Canada. Guidelines from Statistics Canada for data use and release were followed. The research adhered to the tenets of the Declaration of Helsinki. 

Sample

We restricted our sample to adults aged 65 and above, since for this age group the risks of eye disease and vision loss are higher and the government coverage for routine eye examinations varies.⁷ In addition, retirement can lead to reduced income and loss of private insurance coverage through employment, which means the availability of public insurance for eye examinations is more important for this age group. To make a valid comparison we included only individuals self-identified as “white” in the analysis. Nonwhites were excluded because the prevalence of glaucoma and vision loss in nonwhites differs from that in whites,^17,18 and the sample size for nonwhite Canadians in the survey was too small to be analyzed as an independent group. Also excluded were people who moved to another province within the follow-up period (2.2% of the sample), because their government insurance might have changed. 

Based on information collected in the first cycle, we established three cohorts in 1994/1995. Cohort 1 consisted of participants free of glaucoma by excluding individuals who self-reported having glaucoma at baseline. Cohort 2 consisted of participants free of cataracts by excluding individuals who self-reported having cataracts at baseline. Cohort 3 consisted of participants free of vision loss by excluding individuals who self-reported being unable to see close or distance even when wearing glasses or contact lenses at baseline. 

Variables

Exposure.

Government coverage of routine eye examinations was our main study exposure and was determined based on the reported province of residence by respondents in 1994/1995. Individuals living in the provinces of British Columbia, Alberta, Ontario, and Quebec, where routine eye examinations are covered annually for residents 65+, were categorized as “insured.” Individuals residing in Saskatchewan, New Brunswick, Newfoundland, and Labrador, and Prince Edward Island, where routine eye examinations for seniors are not publicly funded (i.e., payments to ophthalmologists and optometrists are required for routine eye exams), were categorized as “uninsured.” Residents of Manitoba and Nova Scotia aged 65+ are entitled to receive government-paid routine eye examinations once every two years.⁷ They were included in the “insured” group for the main analysis, and were excluded from the “insured” group in a sensitivity analysis to examine the robustness of the results derived from the main analysis. 

Outcome Variables.

Incident Glaucoma and Cataracts.

Respondents were asked in each follow-up cycle to report chronic health conditions that were diagnosed by health professionals that had lasted or were expected to last 6 months or longer. A total of 21 chronic conditions was listed for selection, including glaucoma and cataracts. A positive answer to the glaucoma or cataracts questions was considered an incident case. If a person reported positively to the glaucoma question and the cataract question, this person was included in both the glaucoma and cataract analyses. 

Self-Reported Vision Loss.

Respondents were asked the following series of questions about their vision: 

1.  
   “Are you usually able to see well enough to read ordinary newsprint without glasses or contact lenses”?
2.  
   “Are you usually able to see well enough to read ordinary newsprint with glasses or contact lenses”?
3.  
   “Are you able to see at all”?
4.  
   “Are you able to see well enough to recognize a friend on the other side of the street without glasses or contact lenses”?
5.  
   “Are you usually able to see well enough to recognize a friend on the other side of the street with glasses or contact lenses”?

In this analysis, a respondent who provided a negative response to any of questions 2, 3, or 4 was considered to have self-reported vision loss. This would include individuals who have permanent, uncorrectable vision loss, and individuals who have vision loss that is potentially correctable, but left uncorrected due to lack of access to screening, diagnosis, and surgery or affordable corrective eyewear. 

Covariates.

A number of covariates were included to account for potential confounding effects. Age and sex of respondents were self-reported. Education was divided into two levels (“less than secondary graduate” and “secondary graduate or higher”) based on the highest level of education attained by respondents at baseline. Income data were divided into quartiles using the mean of annual income levels reported by the respondent over the follow-up period. Smoking status (ever smoked or never smoked) was defined according to history of cigarette smoking. 

Statistical Analysis

Incident cases of glaucoma, cataracts, and self-reported vision loss in the corresponding cohort were counted based on first-time reporting of these vision conditions during the follow-up period. Follow-up time was calculated as the time period from baseline to the onset time of the conditions in question, the last follow-up survey for respondents who had died or were lost to follow-up, or the final ninth NPHS follow-up survey in 2010/2011, whichever came first. The onset time for conditions under consideration was defined as the midpoint between the time when the last negative response was given and the time when the first positive response was given to the relevant questions. Reporting time was recorded as month and year of interview. When the interview month and year were missing, they were imputed with the midpoint of the corresponding survey cycle (2% of responses). Incidence rates were calculated as the number of incident cases reported per 1000 person-years of follow-up. 

Multivariate log-Poisson regression model was used with a person-time offset term to estimate the incidence rate ratios (IRRs).¹⁹ The IRRs compare incidence rates of glaucoma, cataracts, and self-reported vision loss in insured versus uninsured populations. Factors adjusted for included age, sex, education, and income. Smoking also was included in models for cataracts and self-reported vision loss, since smoking has been identified as a risk factor associated with cataracts and age-related macular degeneration.^20,21 All analyses were weighted by sampling weights to account for the complex survey design, sample selections, adjustments for nonresponse, seasonal effect, and poststratification. The 95% confidence intervals (CI) were derived using the bootstrap weights provided by Statistics Canada to account for sampling design. All analyses were conducted using statistical software STATA 12 (StataCorp, College Station, TX, USA). 

Results

There were 2618 white Canadians aged 65 and above included in the analysis. The characteristics of the study cohorts at baseline are shown in Table 1. The smallest cohort was the cohort without cataracts (n = 1956) and the largest cohort was those without glaucoma (n = 2189). The population residing in provinces with government insurance for routine eye examinations had higher levels of income compared to those in the uninsured provinces. 

Table 1

 

Baseline Characteristics of White Canadians Aged 65+ in the National Population Health Survey in 1994/1995

	Without Glaucoma at Baseline		Without Cataracts at Baseline		Without Self-Reported Vision Loss at Baseline
	n= 2189		n= 1956		n= 2117
	Insured	Uninsured	Insured	Uninsured	Insured	Uninsured
Sex, %
Male	42.9	44.1	45.0	45.1	43.5	44.6
Female	57.1	55.9	55.0	54.9	56.5	55.4
Age
Mean	72.9	73.3	72.6	72.8	72.7	73.0
Education, %
<Secondary graduation	52.9	60.0	52.7	59.1	51.4	58.7
≥Secondary graduation	47.1	40.0	47.3	40.9	48.6	41.3
Income quartile, %
1st, poorest*	14.5	21.7	14.6	20.9	14.4	21.4
2nd	22.4	29.6	21.1	29.1	21.5	29.2
3rd	27.8	24.0	28.1	23.7	27.5	24.3
4th, highest	35.2	24.7	36.2	26.3	36.6	25.2
Missing
Smoking, %
Never	38.1	39.6	36.9	38.7	37.5	39.3
Ever	61.9	60.4	63.1	61.3	62.5	60.7

*  P < 0.05 for insured versus uninsured.

The incidence rates of glaucoma, cataracts, and self-reported vision loss are shown in Table 2. Lower incidence rate of self-reported glaucoma was found in seniors residing in uninsured provinces (8.1/1000 person-years; 95% CI, 5.5–10.7) compared to seniors residing in insured provinces (12.8/1000 person-years; 95% CI, 10.5–15.1). A lower incidence rate of cataract also was found in the uninsured (67.2/1000 person-years; 95% CI, 55.7–78.6) versus the insured population (75.7/1000 person-years; 95% CI, 69.2–82.2). The incidence rate of self-reported vision loss was higher in the uninsured group (26.6/1000 person-years; 95% CI, 20.2–33.0) than in the insured (22.5/1000 person-years; 95% CI, 20.0–25.5). The effect of education level differed by provincial insurance status. The incidence of glaucoma and cataracts was lower in those with lower education level in the uninsured provinces, with the opposite finding in the insured provinces. 

Table 2

 

Incidence Rates (per 1000 Person-Years, 95% Confidence Intervals in Parenthesis) of Self-Reported Glaucoma, Cataracts, and Self-Reported Vision Loss in White Canadians Aged 65+ Studied From 1994/1995 to 2010/2011 in the National Population Health Survey

	Overall	< Secondary Graduation	≥ Secondary Graduation
Glaucoma	12.3 (10.2–14.4)	13.8 (10.5–17.0)	10.8 (8.1–13.6)
Insured*	12.8 (10.5–15.1)	14.6 (10.9–18.2)‡	11.0 (8.0–14.0)
Uninsured†	8.1 (5.5–10.7)	7.0 (3.6–10.3)	9.6 (5.3–13.9)
Cataracts	74.9 (69.0–80.8)	77.5 (68.5–86.6)	72.2 (64.3–80.0)
Insured	75.7 (69.2–82.2)	79.4 (69.4–89.5)	72.0 (63.6–80.4)
Uninsured	67.2 (55.7–78.6)	61.8 (47.5–76.2)	74.4 (56.3–92.5)
Self-reported vision loss	22.9 (20.1–25.7)	24.5 (20.3–28.7)	21.5 (17.6–25.4)
Insured	22.5 (20.0–25.5)	24.1 (19.6–28.6)	21.3 (17.1–25.5)
Uninsured	26.6 (20.2–33.0)	28.7 (20.0–37.4)	24.0 (15.5–32.5)

*  Insured: Included residents of British Columbia, Alberta, Ontario, and Quebec, where yearly routine eye examinations are government-funded, and residents of Manitoba and Nova Scotia, where biannual routine eye examinations are government funded.

†  Uninsured: Residents of Saskatchewan, New Brunswick, Newfoundland, and Labrador, and Prince Edward Island, where government funding for routine eye examinations are not currently available.

‡  Statistically significant at P < 0.05 for insured versus uninsured.

Adjusting for the effects of age, sex, education, and income, multivariate analyses showed that government insured routine eye examinations were associated with an increased risk of self-reported glaucoma (adjusted IRR = 1.59; 95% CI, 1.07–2.37) and cataracts (adjusted IRR = 1.13; 95% CI, 0.93–1.37), and a decreased risk of self-reported vision loss (adjusted IRR = 0.88; 95% CI, 0.67–1.16; Table 3). 

Table 3

 

Adjusted Incidence Rate Ratios (95% Confidence Intervals) From Poisson Regression Model

	Overall	Routine Eye Exams
		Insured	Uninsured
Glaucoma
Insured, vs. uninsured	1.59 (1.07–2.37)*	–	–
Age, continuous by y	1.04 (1.01–1.07)†	1.04 (1.01–1.07)†	1.03 (0.97–1.09)
Female, vs. male	1.45 (1.01–2.08)*	1.54 (1.04–2.28)*	0.60 (0.30–1.18)
Education (vs. higher)
<Secondary graduation	1.32 (0.91–1.91)	1.38 (0.93–2.05)	0.58 (0.30–1.14)
Income, vs. 4th quartile
1st quartile, poorest	0.69 (0.41–1.15)	0.62 (0.37–1.10)	2.17 (0.71–6.66)
2nd quartile	0.90 (0.57–1.43)	0.88 (0.54–1.44)	1.21 (0.38–3.83)
3rd quartile	0.85 (0.55–1.33)	0.86 (0.54–1.37)	0.57 (0.13–2.48)
Cataracts
Insured, vs. uninsured	1.13 (0.93–1.37)	–	–
Age, continuous by y	1.04 (1.02–1.06)†	1.04 (1.02–1.06)†	1.04 (1.02–1.07)†
Female, vs. male	1.18 (0.97–1.40)	1.15 (0.94–1.40)	1.42 (1.03–1.98)*
Education, vs. higher
<Secondary graduation	1.01 (0.85–1.20)	1.04 (0.87–1.25)	0.74 (0.52–1.05)
Income, vs. 4th quartile
1st quartile, poorest	1.06 (0.80–1.39)	1.01 (0.74–1.37)	1.63 (1.03–2.52)*
2nd quartile	1.06 (0.85–1.32)	1.07 (0.84–1.35)	1.04 (0.66–1.63)
3rd quartile	1.11 (0.90–1.38)	1.13 (0.89–1.42)	1.00 (0.67–1.48)
Smoking, vs. never smoked
Ever smoked	1.00 (0.84–1.19)	1.00 (0.83–1.21)	1.00 (0.72–1.38)
Self–reported vision loss
Insured, vs. uninsured	0.88 (0.67–1.16)	–	–
Age, continuous by y	1.07 (1.04–1.09)†	1.06 (1.04–1.09)†	1.07 (1.04–1.11)†
Female, vs. male	1.12 (0.84–1.49)	1.08 (0.79–1.48)	1.56 (0.98–2.50)
Education, vs. higher
<Secondary graduation	1.03 (0.78–1.36)	1.03 (0.76–1.40)	1.15 (0.74–1.77)
Income, vs. 4th quartile
1st quartile, poorest	1.25 (0.86–1.82)	1.26 (0.83–1.90)	1.10 (0.56–2.15)
2nd quartile	1.08 (0.75–1.54)	1.08 (0.72–1.63)	0.98 (0.54–1.77)
3rd quartile	1.04 (0.73–1.48)	1.07 (0.73–1.57)	0.75 (0.43–1.30)
Smoking, vs. never smoked
Ever smoked	1.00 (0.78–1.30)	1.00 (0.76–1.33)	1.07 (0.68–1.71)

*  P < 0.05.

†  P < 0.01.

Consistent with prior reports, increasing age was associated with an increased risk for all of the three vision conditions. When looking at education, we found lower levels of education were associated with an increased risk of glaucoma in the insured population (IRR = 1.38; 95% CI, 0.93–2.05), but a decreased risk of glaucoma in the uninsured population (IRR = 0.58; 95% CI, 0.30–1.14). By income, the poorest quartile in the uninsured provinces exhibited the greatest risk for glaucoma and cataracts compared to those in the highest income quartile. While in the insured provinces, individuals in the poorest quartile had a lower risk for glaucoma compared to those in the highest income quartile (Table 3). 

Results from sensitivity analysis showed that when individuals residing in Manitoba and Nova Scotia (where eye examinations are insured for every two years) were removed from the analysis, the association between insurance status and the incidence of the vision conditions evaluated remained essentially unchanged (IRR for glaucoma increased from 1.59 to 1.60, and IRRs for cataracts and self-reported vision loss remained the same). 

Discussion

We report a significantly decreased incidence of self-reported glaucoma in elderly Canadians living in provinces where routine eye examinations are not publicly funded, compared to individuals living in provinces with government funded routine eye examinations. A decreased risk of cataracts was similarly found in the uninsured group, albeit smaller and statistically nonsignificant. An increased risk of self-reported vision loss, however, was noted in the population without government insurance. This result suggests that glaucoma and cataracts are likely underdiagnosed in the uninsured provinces versus the insured provinces, rather than actually lower levels of disease incidence in the uninsured provinces. This postulation is supported by the fact that the rate of self-reported vision loss was found to be higher in the uninsured population. 

Glaucoma is an optic neuropathy that typically initially affects peripheral vision and is unnoticed by the patient until it is advanced. A comprehensive eye examination can diagnose early glaucoma before the patient having visual symptoms. In contrast, symptoms of cataracts are easily recognized by patients with clouding of central vision. The findings in this paper suggest that when public insurance is unavailable, individuals are more likely to seek eye care only when they experience obvious or severe symptoms (such as reduced vision with cataracts). However, when public insurance is available, individuals may use preventative eye care more frequently, leading to earlier detection of disease. Therefore, the difference between the insured and the uninsured population may reflect the effect of publicly-funded routine eye exams. This may explain why the incidence of glaucoma is significantly higher in insured provinces 

It should be noted that once an eye disease is diagnosed, the cost of eye examinations is covered under provincial health insurance plans in every jurisdiction in Canada. Consequently, public funding for eye examinations primarily affects access to preventative or routine eye care. The importance of removing financial barriers to allow timely access to routine eye examinations cannot be overstated since by the time obvious symptoms have occurred the lost vision from glaucoma and other eye diseases may be irreversible. 

In a sample of patients attending a primary care clinic in the United States, Wang et al.¹³ found that a third of those with ocular pathology were unaware of their condition, with lack of insurance being a risk factor for being unaware. In North America, more than half of glaucoma patients are diagnosed during routine eye examinations.^22,23 Our prior study showed that 13% of Canadian elderly have difficulty paying for basic expenses, such as food and clothing.²⁴ Public insurance, therefore, has a crucial role ensuring equitable access to eye care. In a randomized trial, Lurie et al.¹¹ found that participants receiving free care had improved vision, and that insurance had a greater protective effect among low income participants. Analyzing data from a multicenter study on risk factors for newly diagnosed glaucoma in Canada, Buys and Jin²⁵ found that socioeconomic deprivation was associated with more advanced glaucoma at presentation. These findings highlight the importance of affordable access to routine eye examinations.²⁵ 

In the stratified analysis, we found that individuals in uninsured provinces with lower education levels had a relatively lower risk of self-reported glaucoma and cataracts. This likely suggests a lower glaucoma and cataracts detection rate among less educated individuals residing in the uninsured provinces, possibly due to lack of access to eye care professionals for financial reasons or lack of perceived benefits of preventative eye care. Results also showed a trend toward higher rates of glaucoma diagnosis among individuals in lower income quartiles in provinces with no insurance for eye examinations (IRR = 2.17; 95% CI, 0.71–6.66). This finding was surprising, since we expected that the cost associated with eye examinations would deter individuals with lower income from accessing eye care, which would result in lower detection and reporting of glaucoma. A further analysis of the data found that among people in the lowest income quartile, the co-occurrence of glaucoma and cataracts was fairly common. Individuals in the lower income quartile also were more likely to report incident cataracts, which is consistent with the existing literature.^9,26 One possible explanation for this is that the detection and diagnosis of glaucoma was a result of eye care access initiated by cataract symptoms. However, future research is needed to confirm this suggested explanation. 

A major strength of this study is its longitudinal design with long follow-up period, and the collection of data from a nationally representative sample of elderly Canadians. This allows us to study for the first time the incidence of common vision conditions in relation to publicly funded eye examination policy. Compared to studies based on private insurance, which tends to be available to individuals with relatively good health, higher incomes, and employment,²⁷ public insurance reduces the likelihood of confounding by health and socioeconomic status and provides a natural testing ground for the association between insurance coverage and occurrence of eye disease. This set of data also allows for the estimation of the incidence of various vision conditions in Canada, which have not been reported previously.²⁸ A comparison of our results with prior published incidence reports must take into account that all types of glaucoma and cataracts were included in the current study versus specific classifications of glaucoma or cataracts as identified by clinic examinations in other studies.^29–36 The mean age of our study population also is older than that in prior studies, which also makes the comparisons less meaningful. 

There are limitations to this study. First, there may be biases associated with self-reported vision conditions. Although health surveys have been considered a highly cost-efficient way to measure morbidity burden in a population, self-reporting of health conditions are subjected to recall and reporting errors. However, a validation study in the United States reported a fair degree of agreement between self-reported and medically recorded glaucoma (κ = 0.73).³⁷ Second, self-reported vision loss in this study was based on respondents' ability to see in a day-to-day setting. Without clinical evaluation, it is difficult to determine if self-reported vision loss is medically correctable. Given the universal coverage for diagnosed eye disease in Canada, we suspect a large portion of self-reported vision loss in this study is uncorrectable. However, regardless of the vision loss being correctable or uncorrectable, self-reported vision loss reflects loss of visual function in an individual's daily activity; thus, it may be a more useful measure of real life visual function than clinically measured best corrected visual acuity. In a recent revised definition for visual impairment, the World Health Organization (WHO) recommends “best corrected” visual acuity to be replaced by “presenting” visual acuity (measured with both eyes open with presenting correction, if any).³⁸ Lastly, family history of eye disease was not asked in the survey. Therefore, we were unable to adjust for the influence of family history in the regression model. 

In conclusion, we report that lack of publicly funded vision care insurance is a potential causal factor associated with decreased incidence of self-reported vision conditions. Our results suggested that the lack of government funded eye examinations lead to lower rates of self-reported glaucoma and cataracts, likely as a result of reduced detection and diagnosis. Lack of government-funded eye examinations increases the incidence of self-reported vision loss, likely due to later diagnosis and treatment. Considering the high prevalence of vision loss among the elderly and its financial burden to health care systems and quality of life, providing public funding and universal access to preventive routine eye examinations would likely be a cost-saving strategy to government and society, especially for individuals with lower levels of income and education who have significantly reduced access to vision health services. However, this hypothesis must be tested in future studies. 

Acknowledgments

Study abstract presented at the annual meeting of the Association for Research in Vision and Ophthalmology, Orlando, Florida, United States, May 8, 2014, and the annual meeting of the Canadian Ophthalmological Society in Halifax, Nova Scotia, June 6, 2014. 

Supported by The Canadian Institutes of Health Research (CIHR; CIHR SEC 117120, CIHR HRA 126901). The authors alone are responsible for the content and writing of the paper. 

Disclosure: C.H. Chan, None; G.E. Trope, None; E.M. Badley, None; Y.M. Buys, None; Y.-P. Jin, None