|Year : 2015 | Volume
| Issue : 2 | Page : 56-60
Prevalence of presbyopia in rural Abuja, Nigeria
Rilwan Chiroma Muhammad1, Mustapha A Jamda2, Lokhur Langnap3
1 Department of Ophthalmology, College of Health Sciences, University of Abuja, Abuja, Nigeria
2 Department of Community Medicine, College of Health Sciences, University of Abuja, Abuja, Nigeria
3 Department of Ophthalmology, University of Abuja Teaching Hospital, Abuja, Nigeria
|Date of Web Publication||2-Mar-2016|
Rilwan Chiroma Muhammad
Department of Ophthalmology, College of Health Sciences, University of Abuja, PMB 117, Gwagwalada, Abuja
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: This study aimed to determine the prevalence of presbyopia in rural Gwagwalada, Abuja, Nigeria.
Materials and Methods: A population-based cross-sectional study was conducted, using cluster random sampling to select 15 clusters of 40 participants each. The examination consisted of distance visual acuity measurement using the LogMAR chart at 4 m in ambient light, subjective distance refraction, and ophthalmoscopy. Near visual acuity was assessed at 40 cm with distance correction on for those who required it. Spherical plus lenses in increments of 0.5 diopter were added until the participant was able to read N8 or no further improvement occurred. A participant was defined as having presbyopia if he or she required an addition of at least 1.00 D in either eye to improve near vision to at least N8 or the participant was unable to read N8 at 40 cm with the distance correction in place if required.
Results: The prevalence of presbyopia in all age groups was 53.4% [95% confidence interval (CI): 48.9-57.9]. On multivariate analysis, female gender [odds ratio (OR): 2.37, 95% CI: 1.58-3.56] and increasing age (OR: 3.42, 95% CI: 1.65-7.10) were associated with presbyopia. Analysis of degree of presbyopia by gender showed that females had more severe presbyopia than males (mean 2.46D vs 2.17D, respectively; P = 0.001).
Conclusion: This study revealed the high magnitude of presbyopia among communities where reading is uncommon in rural Nigeria. This study further emphasizes the need for provision of near vision spectacles not only to literate communities, but also to communities where reading is uncommon, as forms of near work other than reading, such as threading a needle, cutting fingernails, and sorting out grains, are commonly performed.
Keywords: Abuja, presbyopia, prevalence, rural
|How to cite this article:|
Muhammad RC, Jamda MA, Langnap L. Prevalence of presbyopia in rural Abuja, Nigeria. Ann Nigerian Med 2015;9:56-60
| Introduction|| |
Presbyopia, which is defined as age-related loss of accommodation, is the most common physiologic ocular change after the age of 40 and causes universal near visual impairment with increasing age.  Without optical correction, presbyopia results in an inability to perform the once effortless near tasks at a customary working distance without experiencing visual symptoms.  Those involved in more frequent or more demanding near vision tasks are likely to have more difficulty. 
Few population-based studies have been published on either the age-related prevalence or the incidence of presbyopia.  This is due to the perception that presbyopia is unimportant in locations where reading is uncommon: Little attention has been paid to presbyopia in the developing world where literacy rates are very low.  As a result, there are insufficient data on presbyopia in different populations and age groups in the developing world, particularly sub-Saharan Africa.  A few population-based surveys of presbyopia in the developing world have found a high prevalence that increases with age. ,,,,,
This study was carried out to determine the prevalence of presbyopia and its relationship with age, gender, and education in rural Abuja, Nigeria.
| Materials and Methods|| |
The study is a population-based cross-sectional study of adults aged 40 years and above that was conducted in the Gwagwalada Area Council of Abuja between June and July 2008.
Gwagwalada is one of six Area Councils that make up the Federal Capital Territory, Abuja consisting of about 90 towns and villages and a population of 291,000 inhabitants, of whom 58,000 are adults aged 40 years and above.  The inhabitants of Gwagwalada are mostly farmers, with some civil servants.
Ethical approval was obtained from the London School of Hygiene and Tropical Medicine's ethics committee and the Department of Health, Gwagwalada Area Council. Informed consent was also obtained from each subject.
The minimum sample size was calculated to be 561 but was increased to 600 to allow for 7% (39) nonresponse. Prevalence of presbyopia was taken as 55%,  precision of 5% with a 95% confidence interval (CI), and a design effect (clustering effect) of 1.5. Fifteen clusters were randomly selected from the 45 available, and 40 participants were enrolled in each cluster. Households were selected using the random walk method. A bottle was spun at the center of each cluster in order to determine the direction to start household selection; households in the direction the bottle pointed to were selected until the required number was recruited. Only 1 respondent was recruited per household.
Inclusion and exclusion criteria
All individuals resident in selected clusters aged 40 years and above were invited to participate. The following exclusion criteria were used.
(1) Age less than 40 years; (2) Individuals with distance visual acuity of less than 6/60 and no improvement noticed with pinhole testing; (3) Inability to test vision although the subject was not blind. (4) Visual acuity testing precluded by known ocular pathology.
All subjects excluded for visual impairment reasons were examined by the ophthalmologist and referred to the eye center.
Demographic information regarding age, gender, and education were entered into a questionnaire administered by trained interviewers.
Definition of presbyopia
A subject was defined as presbyopic if he or she could not read the N8 optotype at about 40 cm with the distance correction in place if required.
Examination and interview procedures
This was conducted by a team made up of an ophthalmologist, an ophthalmic resident doctor, and a research assistant. Distance visual acuity was tested in all subjects using a LogMAR chart at 4 m in ambient outdoor illumination under a shade. Correct identification of three out of four characters in a line constituted success at reading that line.
Distance refraction was then done for subjects with visual acuity less than 6/18 after demonstrating improvement of at least one line when tested with a pinhole. The refraction was conducted using a trial lens set with the addition of plus or minus lenses in 0.5 diopter increments until the subject read 6/6. To reduce testing time in data collection, astigmatism was not corrected for.
Near vision was then tested using a near vision LogMAR "E" chart with ambient light. A string was attached to the near vision chart to ensure a measurement distance of 40 cm from the eyes. Visual acuity was measured binocularly and recorded as the smallest line with at least three of the four optotypes read correctly. The distance correction was put in place for those that required it before near vision testing was done. Spherical plus lenses were added in increments of 0.5 diopter until the subject was able to read N8 (World Health Organization standard) or no further improvement occurred. Subjects that presented with a vision of 6/6 were assumed emmetropic and tested for near vision as described. Subjects needing presbyopic glasses were provided them free of charge, while patients with reduced visual acuity not improved by refraction and those needing distance correction were referred appropriately. The same ophthalmologist did all the refractions.
Statistical analysis was done using Stata 10 statistical software (StataCorp, Texas, USA) and Statistical Package for Social Sciences 16.0 (Version 16, Chicago, Illinois: SPSS Inc.).
The following primary analyses addressed the study aims and objectives:
- Prevalence rates with CIs were calculated for uncorrected near visual acuity.
- Multiple logistic regression was used to investigate the association of age, gender, and literacy with near visual impairment.
| Results|| |
Of the 590 subjects enumerated, 461 (78%) participated in the study and were fully examined. Thirty-one (5%) were not eligible, based on the exclusion criteria. Seventy-seven (13%) were not available on the examination day and 21 (4%) refused to participate.
The mean age of the participants was 52.5 years with a median age of 50 years and age range of 40-85 years. Three hundred thirty-three participants (73%) had little or no education, while 288 (62.5%) were males. Two hundred seventy-one of the participants (58.8%) were manual workers. Two hundred eighteen participants (47%) belonged to the age group 40-49 years, [Table 1].
The crude prevalence of presbyopia was 53.4% (95% CI 48.9-57.9), with increasing prevalence with age (test for trend, P = 0.001). Age-adjusted data showed a higher prevalence among females than males (65.9% against 45.8%; P < 0.001). Analysis of degree of presbyopia by gender showed that females had more severe presbyopia than males (mean 2.46D against 2.17D, respectively; P = 0.001).
There was a significantly higher prevalence of presbyopia in females compared with males. The degree of presbyopia increased as age increased and females had a higher degree of presbyopia across all groups [Table 2].
There was a significant association between presbyopia and age, but no association between presbyopia and educational level, [Table 3] and the mean severity of presbyopia increased as the age group increased [Figure 1].
The results of the multivariate analysis suggest that increasing age and female gender are significantly associated with higher prevalence of presbyopia [Table 4].
| Discussion|| |
This survey provides population-based data on the prevalence of presbyopia in a random sample of adults aged 40 years and older in the Gwagwalada Area Council of Nigeria. Results indicate a prevalence of presbyopia of 53.4% (95% CI 58.8-73.0) among adults age 40 years and older in rural Gwagwalada, Abuja, Nigeria. In our study, there was a statistically significant association of presbyopia with age and female gender.
If the results of our study are extrapolated to the population 40 years and older in Nigeria with an estimated population of 160 million people, where 20% of the population are 40 years and older,  there may be about 32 million people with presbyopia in Nigeria and the population of Abuja could be taken as a rough estimate of the characteristics of the whole country. This is because the population of Abuja is made up of persons from virtually every part of Nigeria.
It is generally believed that presbyopia is a universal age-related phenomenon, with prevalence approaching 100% in older subjects.  In our study, we found 42 (36%) subjects aged 60 years and older who did not require an addition of at least 1.00D for near vision to be able to see at the N8 level. The reasons for this may be the following two. First, most of these subjects had nuclear sclerosis, which precluded the need for addition for near vision - What is referred to as "second sight of the aged." Second, the effect of miosis resulting from ambient illumination combined with senile miosis might have introduced a pinhole effect and given between 0.5D and 1.2D of focus, thus making some subjects be able to read N8.  Indoor testing with standard illumination was not possible in this rural setting where power supply is erratic and not widely available.
Another population-based study of presbyopia in Nigeria examined adults aged 18-49 years and found a prevalence of 33%, but since the methods for presbyopia definition were not well described in the study, a proper comparison cannot be made.  Several other clinic-based studies in Nigeria have found presbyopia as one of the most common eye conditions seen in the clinic. ,
A population-based survey of presbyopia in rural Tanzania found a prevalence of 61.4%.  In our study, a majority of the subjects (47.3%) belonged in the age group 40-49 years, whereas the Tanzanian study had a comparable number of subjects in all age groups; since the prevalence of presbyopia tends to increase with age, this might have accounted for the lower prevalence in our study. In comparison with another study done in Zanzibar, the prevalence was 89.4%.  The lower prevalence observed in our study may be due to the effect of outdoor testing resulting in pupillary constriction and increased field of focus, whereas in the Zanzibar study, standard indoor lighting was maintained throughout the survey. It may also be that because the Zanzibar study had fewer persons in the age group 40-49 years and the majority of the subjects were older, a higher prevalence of presbyopia was obtained. Compared with the Andhra Pradesh (India) eye disease study where subjects aged 30-39 years were included and the prevalence of presbyopia was 55.3%,  the lower prevalence obtained in our study may be as a result of the effect of outdoor testing. The Andhra Pradesh study, similar to the Zanzibar study, made use of standard indoor illumination for testing.
Several studies from different parts of the world have suggested a higher prevalence of presbyopia among females compared with males. ,, Our study also found higher prevalence in female subjects compared with males; females also had a higher degree of presbyopia across all age groups, similar to the findings of the study in Tanzania.  The prevalence of presbyopia was not associated with education, consistent with the findings of the Andhra Pradesh and Zanzibar studies.
The standard examination procedures, the population-based cluster random sampling, and the fairly high response rate (78%) are considered to be the strengths of this study.
Although distance vision was corrected for, it is possible that some low hypermetropic persons may have been misclassified as having presbyopia and thus we may have overestimated the prevalence of presbyopia. This may, however, not significantly affect the results, as the number of individuals who require refractive correction was small. The fact that the subjects were aware that they might receive free near vision spectacles might have influenced their responses. Examinations carried out in ambient outdoor illumination results in miosis, and this effect combined with senile miosis may have introduced a pinhole effect and produced 0.5-1.2D of focus, enabling some subjects to comfortably read N8. This might have reduced the number of presbyopic persons in the sample.
In summary, this population-based study of the prevalence of presbyopia in rural Nigeria gives an idea of the magnitude of the problem in Nigeria. There is therefore a need to increase the availability of new, good-quality, affordable, and readily accessible spectacles in rural settings through an innovative tertiary hospital- and community-based approach, identifying individuals with presbyopia within the community and providing them with good-quality refraction and low-cost spectacles.
We acknowledge Dr. GV Murthy for his technical support/contribution, and the Commonwealth Scholarship Commission, the British Council, and Sight Savers International for providing financial support for this project.
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[Table 1], [Table 2], [Table 3], [Table 4]