Burden and determinats of blindness and visual impairment among elderly in the Dikgale Health and Demographic Surveillance System (HDSS), Capricorn District, Limpopo Province, South Africa

Abstract

The burden of visual impairment is a major health problem worldwide, especially in the rural and remote areas of developing countries. Visual impairment does not only affect the productivity of the individuals affected, but may also result in a loss of income for those caring for them, which is time consuming. Globally, the majority of instances of visual impairment can be avoided or treated, if detected early. Therefore, it was considered important to evaluate the burden and determinants of blindness and visual impairment in order to institute measures to prevent avoidable blindness.

AIM OF THE STUDY The aim of this study was to investigate the burden and determinants of blindness and visual impairment among the elderly in the Dikgale Health and Demographic Surveillance System (HDSS), Capricorn District, Limpopo Province, South Africa.

METHODOLOGY A cross-sectional analytic and descriptive study design was used. The participants included males and females, 50 years and above, who were permanent residents in the Dikgale HDSS. Optometric procedures were performed and a questionnaire was administered to the people selected as study participants to collect data about the knowledge, need, utilisation of eyecare services and barriers to the use of eye-care services in the area. Optometric procedures performed included case history, presenting visual acuity, pin-hole visual acuity if the presenting visual acuity was less than 6/18, auto and subjective refraction, visual fields using a Novissphere and Amsler’s grid, tonometry, direct ophthalmoscopy through a dilated pupil, and light perception for cases of blindness.

Prevalence rates of blindness and visual impairment were determined by the results obtained from the oculo-visual examinations, such as visual acuity xvii

measurements. Data analysis was done using the Statistical Package for Social Sciences (SPSS) Version 23. Overall prevalence was calculated, as well as prevalence within subgroups defined by gender. To determine the predictive values for the determinants of visual impairment, the Pearson’s Chi square (with a 0.05 significant level) was used in order to eliminate the possibility that the observed results happened by chance.

The odds ratios were calculated and interpreted at a 95% confidence interval to determine the strength of association between visual impairment and risk factors. Binary and multinomial logistic regression analyses were used to describe the relationship between visual impairment and demographics, socioeconomic factors, ocular risk factors and chronic diseases. All reported p-values which were two-sided and p-values <0.05 were considered significant. Results are presented in narrative and tabular forms and as figures. The study used descriptive analytical methods to describe the outcome of the research.

RESULTS Of the 1000 selected subjects for the study, a total of 704 participated (i.e. completed the questionnaire and had the clinical tests performed on them), in other words, a response rate of 70.4%. The participants included 508 females and 196 males. All participants were Black South Africans and their ages ranged from 50 to 105 years, with a mean age of 65.6±10.3. The prevalence of bilateral visual impairment meeting the criteria in the better eye was 26.4% (186) of the 704 observed respondents. The majority of the participants had moderate visual impairment, with a similar prevalence in males and females. Many participants used tobacco products (278 or 39.4%). Cataracts (46.2%) and refractive error (40.3%) continue to be the leading causes of visual impairment, followed by corneal disorders (4.9%) and glaucoma (4.3%). The prevalence of low vision increased with age (p<0.001), but there was no significant difference between females (62.0) and males (58.5).

The odds ratio of having visual impairment increased significantly with age ranging from OR 1.2 (95% CI, 0.6-2.3) in the age group 60-69 to OR 3.8 xviii

(95%CI, 1.6-9.0) in the age group 80+. The likelihood of having visual impairment increased with tobacco use OR 1.9 (95%CI, 1.1-3.3). Not using available eye-care services increased the risk of having visual impairment OR 1.3 (95%CI, 0.8-2.2). Refractive error and pathological disorders were significantly associated with all the different degrees of visual impairment. Tobacco use was only significantly associated with moderate visual impairment and not significantly associated with severe visual impairment. Unemployment and lack of education are likely to increase the burden of visual impairment among the participants when looking at p-values for trends.

CONCLUSION There is a high prevalence of presenting visual impairment in the 50+ age group in the Dikgale HDSS. Most of the leading causes of visual impairment are preventable and/or treatable, which can be achieved by appropriate screening strategies. Therefore, there is a need to embark on eye care promotion and awareness campaigns; and to provide low-cost, quality spectacles and cataract surgeries. Better education about prevention of blindness and visual impairment will help to minimise this burden.