The role of cultural norms, religion, traditional medicines and procedures such as couching (a relatively common, crude, procedure involving use of a common tool to push the lens into the aqueous portion of the eye), or inappropriate pharmaceutical use in the pathways to vision care is of particular interest, as these have been explored in other communities in the past, but specific interventions to alter these paradigms has not been fully investigated (Gilbert et al., 2010; Isawumi, Kolawole, & Hassan, 2013; Mahdi et al., 2014; Onwubiko et al., 2014). The cost of surgical treatment of cataracts are largely prohibitive in the areas where the burden of cataracts is the greatest, such as rural Nigeria (Gilbert et al., 2010; Odugbo, Mpyet, Chiroma, & Aboje, 2012).
Accordingly, a better understanding of the precipitating factors for cataract development in these regions is essential to reduce the burden of this disease on a large scale in this region. Investigating the prevalence of risk factors and risk reducers for cataracts in this population, the baseline degree of understanding of these factors within the patient population, and the treatments that patients currently seek for their cataracts is crucial to targeted development of future medical outreach and educational programs in the region. Other studies have described the inverse relationship between socioeconomic status, educational achievement and cataracts and we aim to validate these findings with this study, albeit in a novel region—South-Eastern Nigeria Ulldemolins, Lansingh, Valencia, Carter, & Eckert, 2012). Additionally, this study is the first to our knowledge to investigate the association between cataracts and health care behaviors, such as frequency of medical visits and method of obtaining prescription medications. This study also uniquely investigates the relationship between preventive behaviors, such as frequency of brimmed hat or UV-protective sunglasses use, with cataracts in the setting of a rural population in sub-Saharan Africa.
2. Materials and methods
2.1. Design of questionnaire
A questionnaire was designed to evaluate the patient’s socioeconomic status, medical history, dietary habits, as well as their knowledge of visual disease risk factors and risk reducers. Socioeconomic status and educational achievement were graded in order to quantify differences in comorbidities, general health behaviors, and knowledge of preventive visual health measures.
2.2. Subject selection
A case-control design was used with 61 subjects selected from over 2,000 mission attendees over a three-day period. Subjects were aged 40–88 years old. Cataract was defined as evidence of 2+ or more nuclear sclerosis in either eye as determined by a licensed optometrist or ophthalmologist. About 28 subjects were female and 33 subjects were male and 32 subjects had cataracts and 29 subjects had no cataracts. The study sample size of 61 subjects (32 cataract cases, 29 non-cataract controls) provided 43–88% power to detect anticipated large odds ratios ranging from 3.0 to 6.0 for comparing the incidences of major comorbidities and risk factors between cases and control at the two-sided 0.05 significance level, assuming incidence rates in the control group ranging between 30 and 60%.
2.3. Data analysis
Categorical variables were summarized in terms of frequencies and percentages while continuous variables were summarized in terms of means ± standard deviations (SD). Logistic regression analysis, Chi-square or Fisher’s exact test was used to compare categorical variables between cases and control. Odds ratios (OR) were reported along with the corresponding 95% confidence intervals. The comparisons of continuous variables (social economic scores, hours of unprotected sun) were compared between cases and controls using a two-sample t-test. All p-values were two-sided and p < 0.05 was used to define statistical significance. Data analysis was conducted using SAS software (SAS Institute Inc., Cary NC), version 9.4.
The most common comorbidities in both the cataract and no cataract groups were refractive error (50% of cataract group, 73% no cataract group), hypertension (46% cataract group, 32% no cataract group), arthritis (43% cataract group, 38% no cataract group), and ocular allergy (39% cataract group, 38% no cataract group). No significant difference in comorbidities was observed between the cataract and no cataract groups (Figure 2).
In terms of schooling, the no cataract group had a significantly higher educational status (p = 0.013). Of those with cataract, 11% had no formal education while all of the no cataract cases had at least some formal education. In subjects with cataract 43% had proceeded through primary school only compared to 12% of those with no cataract. Subjects without cataracts had a larger proportion of people reporting a post-secondary education or higher (50% of no cataract controls versus 18% in cataract cases) (Figure 3).
In addition, the graded socioeconomic status of the no cataract group was significantly higher than the cataract group (20.9 ± 2.9 vs. 18.8 ± 3.0, p = 0.011). Factors that contributed to socioeconomic score include ownership of a motor vehicle, number of individuals sleeping to a bed in the household, and drinking water source (Figure 4).
Between both groups, the frequency of medical visits was low. Although, 31% of the no cataract group reported not seeing a doctor in over 3 years compared to 11% in the cataract group, this was not statistically significant (p = 0.234) (Figure 5). In line with the low rate of preventive medical visits, both groups had an equally high rate of obtaining medications without prescription (61% of cataract group, 58% of no cataract group, p = 0.999).
Suspected cataract risk factors and risk reducers including unprotected sun exposure, traumatic eye injury, and multivitamin use were compared between groups but no significant difference was observed in any category. Both cataract and no cataract groups had equally poor knowledge of risk factors or reducers of cataracts (Table 1).
Risk factors and risk reducers in patients with and without cataracts
|Question||No cataracts (N = 26)||Cataracts (N = 28)||p-value|
|Hours unprotected sun||3.4||2.9||3.9||2.2||0.305|
|Sell & eat farm products?||0.320|
|Traumatic eye injury||2||8||6||21||0.253|
|Chemical exposure to eye||0||0||4||14||0.112|
|How often do you wear sunglasses?||0.318|
|How often do you wear a brimmed hat?||0.831|
|How often do you take vitamins?||0.802|
Previous studies in other regions have suggested that educational achievement is protective of cataract formation, which is in agreement with our findings in this study that the group without cataracts had higher level of formal education (Rabiu, 2001). While the causal mechanism of this correlation is unknown at this time, it is logical that obtaining a higher level of formal education would result in better healthcare choices or increased use of cataract preventive measures. This may include personal healthcare, hygiene, lifestyle choices, improved diet, and avoidance of smoking cigarettes, which has been linked to cataracts in previous studies (Nam et al., 2015). Contrary to this premise, our study did not find any difference in the use of cataract risk reducers or preventive measures in the cataract or no cataract group, such as sunglasses or hats for sun protection, or multivitamins. This could be that despite the no cataract group having more knowledge of cataract risk reducing measures, dire socioeconomic factors like lack of finances affected their health choices.
Previous investigations of rural Nigerian communities have shown that the primary barrier to access to cataract treatment is financial burden (Mahdi et al., 2014). Indeed, higher socioeconomic status is preventative of cataract formation in this community. Similar to educational achievement, higher socioeconomic status conceivably facilitates decision-making that would be preventive of cataract formation, including improved dietary choices, hygiene, and medical care. While our survey did not find significant differences in these categories, it is possible that evaluation of other factors, such as family culture and attitudes towards healthcare, and motivation to utilize discretionary funding for health-promoting practices, could reveal a mechanism for the impact of socioeconomic status on cataract prevention. Elucidating the specific factors that account for the impact of lower socioeconomic status on cataract formation are important targets for future research.
In our study, a low frequency of medical visits in this population was observed regardless of socioeconomic status. This is a reflection of the general lack of resources in this community – having a relatively higher socioeconomic status does not imply adequate resources to regularly visit a medical doctor. The lack of access to health care may be a contributing factor to cataract development, as well as to the other various diseases observed at the community medical outreach. While the value of incorporating preventive eye-care into primary care in sub-Saharan Africa is still in question by some (du Toit et al., 2013), given the lack of knowledge of behaviors that precipitate and ameliorate cataract formation described below, a lack of regular contact with medical professionals appears to be a missed opportunity for one-to-one patient education and reinforcement of knowledge on these factors.
To our knowledge, no other study has investigated the relationship between the method of obtaining prescription drugs and cataract formation in a resource-limited setting. In line with the lack of regular medical visits, both study groups primarily obtained medications at a pharmacy without prescription. This is likely due to the inadequate pharmaceutical and healthcare policies, as well as lack of enforcement of federal drug regulation in Nigeria. While there was no significant increase in cataract formation associated with obtaining prescription medications without prescription, inappropriate use of certain drugs may still be a minor factor contributing to a small proportion of cataracts in this region, as some drugs have been strongly linked to cataract formation, such as prednisolone (Fryer et al., 1994).
Of the various specific cataract risk factors and risk reducers that were investigated, no significant differences were observed between the cataract and no cataract group for any factor. Specifically, UV radiation exposure, multi-vitamin use, prior ocular injury, diet, and frequency of medical visits were not shown to be significantly different between subjects with and without cataracts, While it is surprising that none of the risk factors or reducers was significantly altered between the study groups, it is very possible that the various factors, especially well-known factors such as ultraviolet exposure, are additive and significant contributors to cataract development in this population. However, further studies should strive to elucidate any other specific factors that may be adding to the cataract burden in this region. This could include behaviors that were not assessed in this survey, including estimates of lifetime ultraviolet exposure (the current survey simply assessed how much time the patient spends outdoors on average at the time the survey was administered).
Other limitations of this study include the relatively small study group and the lack of grading of cataracts with various risk factors (all cataract subjects had 2+ nuclear sclerosis, but the severity of cataract (mature, hypermature) and distinction of type of cataracts (nuclear, cortical, posterior subcapular, etc.) beyond this was not graded. Additionally, specific medications that the subject was currently taking were not assessed, as certain medications like steroids have been shown to increase risk of cataract formation, and this may have helped clarify the impact of obtaining prescription drugs without prescription.
In conclusion, the prevalence of cataracts in this rural community is high. Having a higher socioeconomic status or higher educational achievement is protective of cataract formation in this community. Additionally, given the limited resources in the region, regular medical check-ups at this time are not the status-quo and this is not likely a modifiable behavior in the short term. Furthermore, cataract surgery in Nigeria is prohibitively expensive, due to both direct and indirect costs of treatment. In a population study done in Northern Nigeria, 61% could not afford treatment, and this was reported as the greatest barrier to cataract surgery (Rabiu, 2001). Given these findings, a mainstay in the efforts to alleviate the cataract burden in this community should focus on subsidized cataract surgeries.
Besides direct intervention with subsidized surgeries, patient education may reduce future cataract burden in this area, as the population’s overall level of visual health knowledge is minimal, and the avenues through which they obtain medications are ineffective, and potentially harmful. Specific educational objectives for improving the visual health and reducing the cataract burden in this community include educating the community on hygiene, diet, and avoidance of known cataract risk factors including unprotected ultraviolet exposure.
Public health implications
- Abdull, M. M., Sivasubramaniam, S., Murthy, G. V., Gilbert, C., Abubakar, T., Ezelum, C., & Rabiu, M. M. (2009, September). Causes of blindness and visual impairment in Nigeria: The nigeria national blindness and visual impairment survey. Investigative Opthalmology & Visual Science, 50, 4114–4120.10.1167/iovs.09-3507 [Article], [Google Scholar]
- Balogh, E., Tóth, A., Tolnai, E., Bodó, T., Bányai, E., Szabó, D. J., … Jeney, V. (2016). Osteogenic differentiation of human lens epithelial cells might contribute to lens calcification. Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease, 1862, 1724–1731.10.1016/j.bbadis.2016.06.012 [Article], [Google Scholar]
- Brockway, J., & Hay, Jr., W. W. (1998, July). Prediction of arterial partial pressure of oxygen with pulse oxygen saturation measurements. Journal of Pediatrics, 133, 63–66. [Google Scholar]
- du Toit, R., Faal, H. B., Etyaale, D., Wiafe, B., Mason, I., Graham, R., … Courtright, P. (2013). Evidence for integrating eye health into primary health care in Africa: A health systems strengthening approach. BMC Health Services Research, 13, 1–15. [Google Scholar]
- Fryer, J., Granger, D., Leventhal, J., Gillingham, K., Najarian, J., & Matas, A. (1994). Steroid-related complications in the cyclosporine era. Clinical transplantation, 8, 224–229. [Google Scholar]
- Fu, Q., Qin, Z., Yu, J., Yu, Y., Tang, Q., Lyu, D., … Yao, K. (2016, June). Effects of senescent lens epithelial cells on the severity of age-related cortical cataract in humans: A case-control study. Medicine, 95, e3869.10.1097/MD.0000000000003869 [Article], [PubMed], [Google Scholar]
- Gilbert, C. E., Murthy, G. V., Sivasubramaniam, S., Kyari, F., Imam, A., Rabiu, M. M., … Tafida, A. (2010, October). Couching in Nigeria: Prevalence, risk factors and visual acuity outcomes. Ophthalmic Epidemiology, 17, 269–275. [Google Scholar]
- Gupta, V. B., Rajagopala, M., & Ravishankar, B. (2014, February). Etiopathogenesis of cataract: An appraisal. Indian Journal of Ophthalmology, 62, 103–110.10.4103/0301-4738.121141 [Article], [PubMed], [Google Scholar]
- Isawumi, M. A., Kolawole, O. U., & Hassan, M. B. (2013, June). Couching techniques for cataract treatment in Osogbo, South West Nigeria. Ghana Medical Journal, 47, 64–69. [Google Scholar]
- Mahdi, A. M., Rabiu, M., Gilbert, C., Sivasubramaniam, S., Murthy, G. V., Ezelum, C., & Entekume, G. (2014, April). Prevalence and risk factors for lens opacities in nigeria: Results of the national blindness and low vision survey. Investigative Opthalmology & Visual Science, 55, 2642–2651.10.1167/iovs.12-10303 [Article], [Google Scholar]
- Mathew, M. C., Ervin, A. M., Tao, J., & Davis, R. M. (2012). Antioxidant vitamin supplementation for preventing and slowing the progression of age-related cataract. Cochrane Database of Systematic Reviews, 2012, CD004567. [Google Scholar]
- Mezu-Ndubuisi, O. J., Mezu-Nnabue, K., Vo, T., & Mezu-Nwaba, N. (2014). Ocular and systemic conditions in a medical mission population in South East Nigeria: Transitioning from integrated medical missions to a community medical center model. 142nd APHA Annual Meeting and Exposition, New Orleans, LA. [Google Scholar]
- Morley, M. G., Morley, K. E., Sanguansak, T., & Kusakul, S. (2015). Blindness and visual impairment. In B. D. Nelson (Ed.), Essential clinical global health (pp. 389–398). New York, NY: Wiley Blackwell. [Google Scholar]
- Murthy, G. V., Gupta, S. K., Maraini, G., Camparini, M., Price, G. M., Dherani, M., … Fletcher, A. E. (2007, January). Prevalence of lens opacities in North India: The INDEYE Feasibility Study. Investigative Opthalmology & Visual Science, 48, 88–95.10.1167/iovs.06-0284 [Article], [Google Scholar]
- Nam, G. E., Han, K., Ha, S. G., Han, B. D., Kim, D. H., Kim, Y. H., … Ko, B. J. (2015, July). Relationship between socioeconomic and lifestyle factors and cataracts in Koreans: The Korea National Health and Nutrition Examination Survey 2008–2011. Eye (London), 29, 913–920. [Google Scholar]
- Odugbo, O. P., Mpyet, C. D., Chiroma, M. R., & Aboje, A. O. (2012, July–September). Cataract blindness, surgical coverage, outcome, and barriers to uptake of cataract services in Plateau State, Nigeria. Middle East African Journal of Ophthalmology, 19, 282–288.10.4103/0974-9233.97925 [Article], [PubMed], [Google Scholar]
- Ono, K., Hiratsuka, Y., & Murakami, A. (2010, September). Global inequality in eye health: Country-level analysis from the global burden of disease study. American Journal of Public Health, 100, 1784–1788.10.2105/AJPH.2009.187930 [Article], [PubMed], [Google Scholar]
- Onwubiko, S. N., Eze, B. I., Udeh, N. N., Arinze, O. C., Okoloagu, M. N., & Chuka-Okosa, C. M. (2014). Mapping the pathways to eye care in a rural South-East Nigerian population: Any implications for practice, eye care programs and policy? Rural Remote Health, 14, 2729. [Google Scholar]
- Pastor-Valero, M. (2013). Fruit and vegetable intake and vitamins C and E are associated with a reduced prevalence of cataract in a Spanish mediterranean population. BMC Ophthalmology, 13, 844.10.1186/1471-2415-13-52 [Article], [PubMed], [Google Scholar]
- Rabiu, M. M. (2001, July). Cataract blindness and barriers to uptake of cataract surgery in a rural community of northern Nigeria. British Journal of Ophthalmology, 85, 776–780. [Google Scholar]
- Roth, A. M. (1977, November). Retinal vascular development in premature infants. American Journal of Ophthalmology, 84, 636–640. [Google Scholar]
- Shweiki, D., Itin, A., Soffer, D., & Keshet, E. (1992). Vascular endothelial growth factor induced by hypoxia may mediate hypoxia-initiated angiogenesis. Nature, 359, 843–845.10.1038/359843a0 [Article], [Google Scholar]
- Ulldemolins, A. R., Lansingh, V. C., Valencia, L. G., Carter, M. J., & Eckert, K. A. (2012, September–October). Social inequalities in blindness and visual impairment: A review of social determinants. Indian Journal of Ophthalmology, 60, 368–375. [Google Scholar]
- Wang, A., Han, J., Jiang, Y., & Zhang, D. (2014, October). Association of vitamin A and beta-carotene with risk for age-related cataract: A meta-analysis. Nutrition, 30, 1113–1121. [Google Scholar]
- Wasunna, A., & Whitelaw, A. G. (1987, September). Pulse oximetry in preterm infants. Archives of Disease in Childhood, 62, 957–958.10.1136/adc.62.9.957 [Article], [Google Scholar]
- Williams, P. T. (2013, June). Walking and running are associated with similar reductions in cataract risk. Medicine & Science in Sports & Exercise, 45, 1089–1096.10.1249/MSS.0b013e31828121d0 [Article], [PubMed], [Google Scholar]
- Yam, J. C., & Kwok, A. K. (2014, April). Ultraviolet light and ocular diseases. International Ophthalmology, 34, 383–400.10.1007/s10792-013-9791-x [Article], [Google Scholar]