The Nigerian national blindness and visual impairment survey: Rationale, objectives and detailed methodology.
BACKGROUND
Despite having the largest population in Africa, Nigeria has no accurate population based data to plan and evaluate eye care services. A national survey was undertaken to estimate the prevalence and determine the major causes of blindness and low vision. This paper presents the detailed methodology used during the survey.


METHODS
A nationally representative sample of persons aged 40 years and above was selected. Children aged 10-15 years and individuals aged <10 or 16-39 years with visual impairment were also included if they lived in households with an eligible adult. All participants had their height, weight, and blood pressure measured followed by assessment of presenting visual acuity, refractokeratomery, A-scan ultrasonography, visual fields and best corrected visual acuity. Anterior and posterior segments of each eye were examined with a torch and direct ophthalmoscope. Participants with visual acuity of < = 6/12 in one or both eyes underwent detailed examination including applanation tonometry, dilated slit lamp biomicroscopy, lens grading and fundus photography. All those who had undergone cataract surgery were refracted and best corrected vision recorded. Causes of visual impairment by eye and for the individual were determined using a clinical algorithm recommended by the World Health Organization. In addition, 1 in 7 adults also underwent a complete work up as described for those with vision < = 6/12 for constructing a normative data base for Nigerians.


CONCLUSIONS
The field work for the study was completed in 30 months over the period 2005-2007 and covered 305 clusters across the entire country. Concurrently persons 40+ years were examined to form a normative data base. Analysis of the data is currently underway.


CONCLUSIONS
The methodology used was robust and adequate to provide estimates on the prevalence and causes of blindness in Nigeria. The survey would also provide information on barriers to accessing services, quality of life of visually impaired individuals and also provide normative data for Nigerian eyes.
Dineen
Brendan
B
International Centre for Eye Health, London School for Hygiene and Tropical Medicine, UK. brendan.dineen@nuigalway.ie
Gilbert
Clare E
CE
Rabiu
Mansur
M
Kyari
Fatima
F
Mahdi
Abdull M
AM
Abubakar
Tafida
T
Ezelum
Christian C
CC
Gabriel
Entekume
E
Elhassan
Elizabeth
E
Abiose
Adenike
A
Faal
Hannah
H
Jiya
Jonathan Y
JY
Ozemela
Chinenyem P
CP
Lee
Pak Sang
PS
Gudlavalleti
Murthy V S
MV
D000293:Adolescent; D000328:Adult; D001766:Blindness / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D002387:Cataract Extraction; D002648:Child; D005654:Fundus Oculi; D006306:Health Surveys; D006801:Humans; D008722:Methods; D009549:Nigeria / Q000453:epidemiology; D010781:Photography; D011184:Postoperative Period; D015995:Prevalence; D012029:Refraction, Ocular; D014065:Tonometry, Ocular; D014787:Vision Tests; D015354:Vision, Low / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D014792:Visual Acuity; D014794:Visual Fields