|Year : 2014 | Volume
| Issue : 3 | Page : 91-95
Ocular morbidity in Sokoto State, Nigeria
Nasiru Muhammad, Adamu Mohammed Dantani
Department of Surgery, Ophthalmology Unit, Usmanu Danfodiyo University, Sokoto, Nigeria
|Date of Web Publication||6-Sep-2014|
Department of Surgery, Ophthalmology Unit, Usmanu Danfodiyo University, Sokoto 840232
Background: There is a paucity of population-based data on ocular morbidity globally. The objectives of the current study were to estimate the prevalence and magnitude of eye disorders and to determine the ophthalmic subspecialty requirements for the population of Sokoto state, Nigeria. The information generated may provide baseline data for planning of a comprehensive eye health services in the state. Materials and Methods: During an all-ages population based blindness survey in December 2005, persons selected through a multi-stage random sampling were examined for any ocular disorder using a magnifying loupe, penlight and a direct ophthalmoscope. Data was entered and analyzed by a statistician. Statistical tests were carried out using Epi info 6 software (Centre for disease control [CDC] Atlanta, Georgia). Results: A total of 4848 persons were examined which gave a response rate of 91%. A total of 943 persons of the sample had an eye disorder in at least 1 eye, giving an ocular morbidity prevalence of 19%. Children aged 0-9 years constituted the highest proportion (37.5%) of the examined subjects. About 57% of the study population were males. Disorders affecting the lens (9.34%) were the most common followed by conjunctival lesions (5.49%). The most common diagnosis was lens opacity (8.1%) followed by conjunctivitis (5.2%). The most common subspecialty requirements in the population are cataract microsurgery (41.7%), and cornea/anterior segment (33%). Conclusion: Our data demonstrates high burden of ocular diseases most of which are either preventable or treatable in the study population. We recommend provision of human resource and technology requirements to meet these demands.
Keywords: Ocular morbidity, ophthalmic subspecialty service, pattern
|How to cite this article:|
Muhammad N, Dantani AM. Ocular morbidity in Sokoto State, Nigeria. Sahel Med J 2014;17:91-5
| Introduction|| |
Ocular morbidity has been described as eye diseases that are either significant to the individual (concerned enough to seek care) or to professionals (who determines the benefit of advice, further review, and/or treatment).  The WHO and an Alliance of International Agencies launched Vision 2020 in 1999 in order to ensure the right to sight by eliminating avoidable blindness world-wide, especially, in the developing countries where 9 out of 10 blind person lives.  The Sokoto state eye care program, established in 2005 is targeted to provide comprehensive eye care services to the population through a system that is affordable and accessible A population-based all ages blindness prevalence survey that was conducted at the takeoff of the program reported a blindness prevalence of 1.9%.  The eye care services have been integrated into the primary health care system in Sokoto state as the 9 th component. Sokoto state, like many developing countries,  does not have population-based data on ocular morbidity. The available few studies suggest that eye diseases probably constitute a significant public health problem though most of them do not result in loss of vision.  The major causes of blindness and visual impairment in Nigeria was updated recently following a National blindness survey.  In Kenya, the prevalence of ocular morbidity (including presbyopia) was 15.52%.  One all-age study in South Korea reported a prevalence of 24.1% 5.4%, 13.4%, 1.5%, and 1.4% for cataract, pterygium, diabetic retinopathy, strabismus and glaucoma, respectively.  In London a study has reported a lens opacity prevalence of 30% in persons aged 65 years and older, 10% for pseudophakia, 3% for glaucoma, and 9% for refractive errors. 
This study determines the pattern of eye diseases in Sokoto state, Nigeria.
| Materials and methods|| |
This is an all-age population-based cross-sectional study conducted in November and December 2005. Sokoto state is located in North Western Nigeria and has Sahel-savannah vegetation. It was estimated to have population of 3.5 million in 2005 and the population is largely Muslim agrarian farmers. There is a Federal teaching hospital and a state specialist hospital in the state capital, several general hospitals across the districts and primary health care centers. Health services are administered through four health zones for convenience i.e. Wurno, Gwadabawa, Dange-Shuni, and Yabo health zones.
A minimum sample size of 5303 persons of all ages was calculated using the Epi-info 6 software. This was based on an estimated Sokoto State population of 3,509,001 (2005 projection); assumed 1.5% prevalence of blindnessin one of the LGAs in Sokoto state;  worst acceptable estimate of 0.4%; design effect of 1.5 being a cluster randomized study; and a confidence interval (CI) of 95%. An additional 10% was then added to cover non-response.
With a cluster size of 80 persons, the minimum sample was expected to be examined in 72 clusters. Sample selection was stratified based on the existing health zones. The number of persons selected in each zone was based on the proportion of population residing in the zone. The list of towns and villages in each zone was used as a sampling frame from which the clusters were selected. Seventeen clusters were selected in Yabo zone (23%), 18 clusters each in Gwadabawa (24%) and Dange-Shuni (25%) zones, and 20 clusters in Wurno zone (28%). Probability proportional to size sampling was used in the selection of the clusters.
In each cluster a ward was selected using simple random sampling, while the study subjects were selected using random walk method at the center of ward, the lowest administrative unit in a community. Only individuals who have stayed at least 6 months in a community were included as described in a published paper. 
The operational definitions for the study were based on the WHO coding instructions for eye examination record.  Glaucoma was defined as a cup disc ratio ≥0.8 based on the rapid assessment of cataract surgical services operational definitions.  Two teams conducted the survey. Each team had an ophthalmologist, ophthalmic nurse, and two research assistants including a village guide. A community health worker enumerated eighty subjects in each cluster and an ophthalmic nurse assessed visual acuity (VA) of those present. Children unable to do VA were assessed, as either believed seeing or blind. The ophthalmologist then examined the study subjects for any ocular disease irrespective of whether it was vision impairing or non-vision impairing and documented in the survey tool. The eye examination was conducted with ×2 magnifying loupe, a penlight and a direct ophthalmoscope. Data was recorded into a modified WHO eye examination record.  Ethical approval was obtained from the Ethics and Research Committee of the National Eye Center Kaduna. Provisions of Helsinki declaration were also observed. The data was entered and analyzed by a statistician using Epi-info 6 software (CDC, Atlanta). Relevant statistical calculations were performed.
| Results|| |
A total of 4,848 persons were examined which gave a response rate of 91%. One hundred and twenty nine persons (2.4%) refused examination. [Table 1] shows the age distribution of the study subjects with children aged 0-9 years constituting the highest proportion of the examined subjects (37.5%). Males constituted 57% of the study population.
Prevalence of ocular morbidity
Nineteen per cent (943 persons) of the study population had an eye disorder in at least 1 eye, giving a prevalence rate of ocular morbidity of 19%. [Table 2] and [Table 3] show the prevalence of various eye disorders based on anatomical location and the specific eye disorders, respectively. Disorders affecting the lens (9.34%) were the most common followed by conjunctiva lesions (5.49%). The most common diagnosis was an obvious lens opacity (8.09%) followed by conjunctivitis (5.24%). The distribution of ocular morbidity shows that lens opacity was highest among those aged 90 or more years (100%), that were followed by age groups 70-79 years (66%) and 80-89 (61%). There was no significant difference between males and females in the prevalence of lens opacity (8.6% vs. 7.5%; P = 0.17). Corneal opacity was highest in those aged 90+ (12.5%), and was followed by those in age groups 70-79 years (8.5%), and 60-69 years (5.8%) with no significant difference between males and females (1.7% vs. 1.4%; P = 0.13). Aphakia largely from couching was higher in females than males (1.05% vs. 0.33%, P = 1.0); while pseudophakia was higher in males than females (0.11% vs. 0.05%, P = 0.87). The Glaucoma prevalence was also higher in males than females (0.93% vs. 0.53%, P = 0.78).
|Table 2: Prevalence of anterior segment disorders in the study population|
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|Table 3: Prevalence of posterior segment disorders in the study population|
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Magnitude of eye disorders in target population
The magnitude of eye disorders in the target population is shown in [Table 4]. The most common disorder was an obvious lens opacity affecting about 299391 subjects (95% CI 270295-329538), followed by conjunctivitis, corneal opacity, aphakia and glaucoma.
Subspecialty need of the population
The subspecialty requirement for the target population is shown in [Figure 1]. The cataract service was the highest required service by the population (41.7%) and was followed by the services of an anterior segment specialist including corneal surgery (33%) and optical services (12.1%).
| Discussion|| |
Our results indicate a high-burden of eye disorders among the study population This is largely due to lack of access to eye care services as there was only one ophthalmologist serving a population of over 6 million as at the time of the current study. The findings of high aphakia and low pseudophakia in women though not statistically significant, may indicate the need for a strategic service delivery that ensure access by women as they seem to be couched by traditional healers at home while the men access care in hospitals. The studies from Osun state Nigeria,  Kenya  and South Korea  are comparable to our study in terms of the study subjects (all-age). The Osun State, Nigeria and Kenyan studies reported lower prevalence of ocular morbidity (13.5% and 15.52% respectively), probably because both populations had better access to eye care services than the current study population. The Osun (Nigeria) , Korean and our study reported cataract (lens opacity) as the most common eye disorder but differed in the other major causes of eye morbidity. Unlike our study in which conjunctivitis, corneal opacity, aphakia and glaucoma were next to lens opacity, the Korean study  reported refractive errors, diabetic retinopathy, pterygium, and strabismus as the major eye disorders. The level of development, climate and availability of eye care services may partly explain the differed pattern of ocular morbidity in different populations.
A study in London  also reported lens opacity as the most common eye disorder followed by pseudophakia and glaucoma, which contrasts our finding of high prevalence of aphakia (from couching).A study in Pakistan  reported a prevalence of non-vision impairing ocular condition (NVIC) of 14.6% (excluding presbyopia). The main NVIC were allergic conjunctivitis (3.7%), bacterial conjunctivitis (3.5%), pterygium/pinguecula (2.6%) and acute/chronic dacryocystitis (1%). This compares with current study as conjunctivitis (from all causes) was next to cataract and the most common NVIC.
The results of our study suggest that specialists in cataract microsurgery and anterior segment surgical services are the highest subspecialties needed by the population. We recommend that more ophthalmologists be trained and the available ophthalmologists should be supported to undergo subspecialist training that is required in providing a qualitative comprehensive care to the population.
| Conclusion|| |
There is a high-burden of eye morbidity in Sokoto State. We recommend infrastructural and manpower development for specialized eye care service in the state.
| Acknowledgments|| |
Sightsavers funded this work. We thank Rabiu MM for his advisory role in the survey and the survey team including Aliyu Umar and Modi Sanyinna, among others for their support.
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[Table 1], [Table 2], [Table 3], [Table 4]