Nigerian Journal of Basic and Clinical Sciences

: 2020  |  Volume : 17  |  Issue : 2  |  Page : 91--96

Cataract surgical coverage and visual outcome using RAAB in birnin gwari local government Area, North West Nigeria

Saudatu Umar Madaki1, Alhassan Mahmoud Babanini2, Saudat Garba Habib3,  
1 Department of Ophthalmology, Federal Teaching Hospital, Gombe State University, Gombe, Gombe State, Nigeria
2 Department of Vitreoretina, National Eye Centre, Kaduna, Kaduna State, Nigeria
3 Department of Ophthalmology, Aminu Kano Teaching Hospital, Bayero University Kano, Kano State, Nigeria

Correspondence Address:
Dr. Saudatu Umar Madaki
Department of Ophthalmology, Federal Teaching Hospital, P. M. B. 0037, Gombe, Gombe State


Context: Cataract is the leading cause of blindness worldwide. It is responsible for 51% of blindness and accounting for 65.2 million blind people worldwide. Cataract surgery has been shown to be one of the most cost effective health care interventions. Aims: To determine the cataract surgical coverage (CSC) and visual outcome using RAAB in Birnin Gwari Local Government Area, North West Nigeria. Setting and Design: Population based cross sectional study. Materials and Methods: Rapid method of assessing avoidable blindness was used (RAAB) in the study. A total of 2162 out of 2530 registered eligible subjects were examined. Two stage cluster random sampling was used to select 59 clusters in 40 villages, and in each cluster, 50 subjects aged 40 years and above were selected using probability proportional to the size. Biodata of all eligible subjects were registered followed by visual acuity (VA) testing. Subjects with VA of <6/18 were examined further to determine the cause of poor vision. Statistical analysis used: The data were recorded in a modified RAAB questionnaire form and were analysed using SPSS version 16.0 program (SPSS Inc., Illinois, USA). Results: Cataract surgical and couching coverage were found to be 31.9% and 19.9%, respectively. Visual outcome for cataract surgery was poor in 37% of the subjects; this was worst in those who had couching. Conclusions: In view of the low CSC, there is a need to provide quality and affordable cataract surgical services in the community.

How to cite this article:
Madaki SU, Babanini AM, Habib SG. Cataract surgical coverage and visual outcome using RAAB in birnin gwari local government Area, North West Nigeria.Niger J Basic Clin Sci 2020;17:91-96

How to cite this URL:
Madaki SU, Babanini AM, Habib SG. Cataract surgical coverage and visual outcome using RAAB in birnin gwari local government Area, North West Nigeria. Niger J Basic Clin Sci [serial online] 2020 [cited 2021 Jan 16 ];17:91-96
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Full Text


Cataract is defined as the opacity of the crystalline lens and is the leading cause of blindness worldwide.[1] It is responsible for 51% of blindness and accounting for 65.2 million blind people worldwide.[2] Blindness due to cataracts ranged from as low as 5% in the United State of America (USA), and the United Kingdom (UK), to 55% in some parts of Africa and to 58.5% in countries such as Peru and Australia.[3] The Nigeria National Blindness survey reported that cataract was the most common cause of severe visual impairment and blindness being responsible for 45.3% and 43%, respectively.[4] The prevalence of cataract-related blindness was 1.8%.[4] There is a large global variation in the prevalence of blindness due to cataracts. The factors explaining these variations and the indicators for monitoring a cataract programme can be a good tool to compare differences across these countries. These indicators include the prevalence and incidence of cataract blindness, cataract surgical rate (CSR), cataract surgical coverage (CSC) and visual outcomes.[5]

Globally, cataract is the single most important cause of blindness, and cataract surgery has been shown to be one of the most cost-effective health-care interventions.[6] Uneventful cataract surgery with the implantation of an intraocular lens is highly effective and results in immediate visual improvement.[7]

Cataract surgical coverage

It is defined as the number of aphakics/pseudophakics divided by the sum of aphakics/pseudophakics and those waiting for surgery.[8] It is a useful indicator for evaluating the performance of the cataract programme and gives information on the remaining work load in the country or region at that point in time. CSC is low or inadequate in many countries or regions,[9] for obvious reasons such as lack of trained workforce and supplies. Even where services are available, there are barriers which keep patients from utilising the services. CSC for eyes reflects the volume of cataract surgery, whereas CSC for people is a measure of the success of cataract surgical programme of VISION 2020 initiatives for eliminating cataract blindness.

In Nigeria, CSC (for eyes) was 5.6% in females compared to 24.5% in males, whereas the CSC (for persons) at <3/60 was 50.3% in males and 28.4% in females.[4]

Other African countries have reported higher CSC for persons compared to Nigeria. Study in western Rwanda[9], reported CSC of 47% at (VA) 0f <3/60, Botswana reported CSC of 73%[10] at (VA) of <6/60 while Kenya reported CSC of 78%[11] at (VA) of <3/60.

Cataract surgical rates

It is the number of cataract operations performed per million population per year.[12] It is an indicator of provision and uptake of cataract services. It is dependent on the existing health-care system supply and demand for cataract surgery.[13] The CSR for Africa is 300/million/year, America 2700/million/year, Eastern Mediterranean 1000/million/year, Europe 2400/million/year, Southeast Asia 2400/million/year, West Pacific 670/million/year.[7],[14] In Nigeria, CSR is 300/million/year[15] and 596/million/year in Sokoto State.[16]

The aim of this study is to determine the CSC and visual outcome in the Local Government Area (LGA) and to determine whether plans to eliminate cataract backlog in the country were put in place to reduce the burden of cataract blindness.

 Materials and Methods

The study adhered to the tenet of Helsinki Declaration. Ethical clearance was obtained from the Ethical Committee of National Eye Centre, Kaduna. Permission to conduct the study was obtained from Birnin Gwari LGA Authorities and Community Leader. Written and informed consent were sought and obtained from all eligible participants after due explanation of the nature of the study in the local language. This was a quantitative, population-based, cross-sectional study carried out in Birnin Gwari LGA on adults (≥40 years) who have resided in the area for ≥6 months.

The minimal sample size was determined using automated programme within the RAAB software package. The parameters used include population aged 40 years and above living in the study area; expected prevalence of blindness in the area was 4% (based on the previous study in Northern Nigeria).[17] Population of Birnin Gwari-252,363 (20% of these total makes up adults 40 years and above-50,472), expected frequency of 4.00% from the previous study, worst acceptable of 5.00%, non-response of 10%, confidence interval (CI) of 95% and design Effect of 1.5. (Worst acceptable is the figure considered to be either above or below the expected frequency and as such 5% was used). These parameters were also used to obtained the minimal sample size.

These reference figures were obtained from the RAAB software manual used in cataract prevalence survey.[18] This gives a sample size of 2935 and a total of 59 clusters with 50 subjects selected from each cluster. The size of the cluster and number of subjects from each cluster is dependent on the design effect used.

A two-stage cluster random sampling was applied. In the first stage, 40 villages were randomly selected from a total of 102 villages, each time recording the name of the village. The required numbers of clusters were mapped out from the selected villages using probability proportional to the size where two to three clusters were selected in larger villages. In the second stage, a specific number of households were enumerated from the selected villages. Enumeration of the households involved the registration of all adults aged 40 years and above. Random sampling was used to select 50 eligible subjects along that area.

Materials: These includes modified Snellen's VA chart (tumbling E” chart), pin hole with multiple holes, rope 6 meters and 3 meters long, battery operated Welch Allyn direct ophthalmoscope (11770, UK), pen torch with extra batteries, pencil with eraser and sharpener, clipboard to hold the forms, map of population unit divided in segments, referral slips, shoulder bag to carry all materials, dilating drugs (guttae tropicamide 1%, guttae phenylephrine 5%), basic drugs (occ chloramphenicol 0.5% and guttae chloramphenicol 0.5%), questionnaire forms (modified RAAB form), consent forms and aphakic glasses (+10DS).

Data collection

Informed consent and personal and demographic data of all eligible subjects were recorded at the time of enumeration. Biodata of eligible subjects were recorded on a modified RAAB form. Each subject was asked about the history of cataract surgery or couching procedure in one or both eyes. Additional information includes type of surgery (if known) and direct cost of surgery.

The patients underwent ocular examination including VA using modified Snellen's tumbling E” chart (single optotype of 6/18 and 6/60 vision), at a distance of six and three meters using a six meters rope, in a broad day light under a shade in order to avoid reflection from the sunlight. Subjects with VA of ≥6/18 were examined further, for the presence of pseudophakia and clear lens using pen torch, whereas those with VA of <6/18 with or without spectacle correction were evaluated further for the presence of cataract blindness, aphakia or pseudophakia and any other causes of decreased vision in that eye using pen torch and direct ophthalmoscopy to view the fundus. All eligible subjects underwent basic ophthalmic examination in their respective communities.

The data were collected between September and October 2015 in stages as follows: the first stage was registration of all eligible subjects and the second stage was examination of the anterior segment including VA. In the third stage, all eyes with vision <6/18 with available correction and had clear cornea were examined further with funduscopy to assess the cause of the visual impairment. In a situation whereby funduscopy was difficult, they had dilated funduscopy. Only the primary cause of blindness or visual impairment was recorded.

Subjects who had a vision-impairing cataract were asked why they did not have cataract surgery, and up to two responses were marked per person in pre-coded categories. Those who had undergone cataract surgery were asked the details about their operation (e.g., place, type and cost of operation). All the information obtained was recorded on a modified RAAB form.

Subjects with minor treatable eye conditions were treated with topical antibiotics ointment and guttae, and those with severe eye disease (for example corneal ulcers or foreign body) were referred to the general hospital for appropriate treatment. Those who were found to have cataract were also referred to have free cataract surgery, which was sponsored by the local government authority.

Data entry and analysis

Microsoft Excel was used for data entry, and SPSS version 16.0 programs (SPSS Inc., Illinois, USA) were used for data analysis to calculate values such as frequencies, percentages and CIs. Chi-square test was used as a statistical test of significance and P <0.05 was considered statistically significant.


A total of 2530 subjects were registered in the survey from the 50 villages, of these 2162 subjects were examined from the registered subjects, giving a participation rate of 85%. The number of registered eligible subjects was less than the minimum sample size of 2935 because some villages were smaller and some have fewer numbers of subject age 40 years and above [Table 1].{Table 1}

Age–sex distribution of sample population

As shown in [Table 2], a total of 2162 subjects comprising 946 males (37.4%) and 1216 females (48.1%) were registered with male-to-female ratio of 1:1.2. The age range was 40–100 years, with a mean age of 61.3 and 54.9 for males and females, respectively.{Table 2}

The overall population mean was 57.8 years ± 13.3 years (standard deviation).

Cataract blindness in the study area

There were 267 subjects with operable cataract, comprising 151 males (56.6%) and 116 females (43.4%). The prevalence of bilateral cataract blindness was found to be 4.7% (95% CI: 4.5%–5.3%): for males 5.9% (95% CI: 5.4%–6.4%) and females 4.6% (95% CI: 3.8%–5.6%). As illustrated in [Table 3], there was no significant difference in the prevalence of cataract blindness between males and females: Chi-square = 0.01, P = 0.932 (CI: 0.54–2.20).{Table 3}

Comparison of pseudophakia, aphakia and place of surgery

A total of 80 subjects had cataract surgery in a hospital, out of whom 14 were aphakic. Sixty subjects had couching and all of them were aphakic, 12 of them had couching in the two eyes.

Cataract surgical and couching coverage

A total number of 78 people had aphakia in at least one eye due to either cataract surgery or couching. Thirteen were bilateral (1 from eye camp and 12 from couching), while the remaining 65 subjects had unilateral aphakia. Out of the total number of aphakics, 18 had cataract surgery and 60 had couching in one or both eyes. Hence, the CSC for VA <3/60 for persons was found to be 31.9% and couching coverage (persons) was 19.9%. Overall cataract surgical and couching coverage for people was 51.6%. No significant difference was observed between cataract surgical and couching coverage, Chi-square = 0.93, P = 0.333 (CI: 0.15–1.64). As depicted in [Table 4].{Table 4}

CSC for eyes was calculated using the formulas below:

* Cataract surgery = (a/a + b + c) × 100

* Cataract couching = (c/a + b + c) × 100

* Both cataract surgery and couching coverage = (a + c/a + b + c) × 100

where a = number of (pseudo) aphakic eyes

b = number of cataract blind eyes

c = number of couched eyes.

x = number of people with unilateral (pseudo) aphakia

y = number of people with bilateral (pseudo) aphakia

z = number of people with bilateral cataract blindness

p = number of people with one eye couched

q = number of people with both eyes couched.

CSC for people was calculated using the formulas below:

* Cataract Surgery = (x + y/x + y + z + p + q) × 100

* Couching = (p + q/x + y + z + p + q) × 100

* Both cataract surgery and couching coverage = (x + y + p + q/x + y + z + p + q) × 100

Cataract surgical outcome

[Table 5] shows the cataract surgical and couching visual outcome (VA) of all subjects who had cataract surgery or couching. Among 87 subjects who had surgery, 37% of them had poor visual outcome; this included the people who had pseudoaphakia and those who had surgical complications. For those that had couching, 73% of them had VA of <1/60 while only 28% improved with aphakic correction.{Table 5}


The participation rate was quite high (85%) and the 15% that were not available could be attributed to the fact that the survey was conducted at the end of the rainy season (September–October 2015) whereby some of the eligible subjects were in the farms harvesting crops despite several revisits to some of the households. Other similar studies reported coverage of 89% in Sokoto,[16] (76%) in Katsina[17] and (73.3%) in Oyo.[19] Higher coverage of 98% was reported in Plateau State of Nigeria,[20] probably because the survey was conducted during the dry seasons where majority of the household members were at home. A coverage of 98.7% was also reported in Kwara State,[21] Nigeria. This was made possible by the immense support given by the community leaders who encouraged the people to participate. Furthermore, the field work was carried out in the afternoon and evening, which allowed those who went to farm, market and civil services to have returned home to participate in the survey as explain by the author.[21]

Higher cataract surgical and couching coverage for people were found in this study. These observations were considerably higher compared to a similar study done in the northern part of the country that found coverage of surgery and couching to be 4% and 18.0%, respectively.[17]

A recent study[22] in Katsina also reported a lower coverage of 28.2%.

It was also observed that men have higher surgical and couching coverage as compared with women as in other similar studies due to the fact that men have more freedom of decision-making and are the ones in control of family financial resources.[4],[16],[17],[20],[21],[22],[23],[24],[25] The higher CSC seen in this study is likely due to regular eye camps/outreach programmes in the area at either free or subsidised rates organised by the local government in collaboration with the Sight Savers International and National (Eye Centre) Institute of Ophthalmology, while the lower coverage seen in the previous studies is likely due to non-availability of cataract services in the area or at best the cataract services are very irregular and expensive where most people cannot afford the cost, as they are very poor, living essentially on subsistence farming as claimed by the author.[17]

Similar studies[20],[23] in Jos, Central Nigeria, a higher CSC of 39.2% and 53.8% were reported although the former study was carried out solely on leprosy patient age 30 years and above who tend to have higher risk of developing cataract as compared to age-match controls due to their comorbidity. The higher coverage seen in the study was due to support from Netherlands leprosy relief programme that support free cataract surgery to such patients.[23]

Higher CSC was also reported in two different studies in Sokoto state 62.1%,[16] 67.1%,[24], and in Kwara state 74.5%.[21]

Couching coverage in this study was found to be lower than 46.1% reported in the national blindness survey, but similar to the finding in Jos (29.7%), Katsina (18%) and Plateau (12%), states of Nigeria.[17],[20],[23] This means couching practices are particularly high in this part of the country and is being performed evidently at a much higher rate than cataract surgery. Free or subsidised cataract surgery is not enough because patients are charged for couching services at even higher cost than cataract surgery. Perhaps patients accept whatever is readily available to them in their localities. Couchers are closer to the community and can penetrate into every corner of the locality.[17]

In other regions of the world like Myanmar,[26] CSC was also found to be as low as 22.3% for people and 24.6% in South Africa,[27] while in Kenya, higher coverage of up to 78.9% (69.6%–84.6%) was reported.[11] Cataract services are available to the majority of the population in these countries and that community uptake is reasonably good.

Poor cataract surgical outcome was observed in a third of the subjects (37%). Couching outcome was even worse (72%). Less than a third had improved VA with aphakic spectacle correction. Similar findings were reported in other studies.[4],[17],[20],[23] Recent study in Katsina[22] reported good visual outcome ( >6/12) in 38% of >6/12 in pseudophakic eyes which increase to 53% after correction with pin hole, the same study also reported good vision in 3.5% of couched eyes which improved to 8.8% with available pin hole correction. Lack of adequate workforce and skilled personnel coupled with lack of appropriate equipment for surgery and inadequate training/re-training of personnel might be a contributory factor to this poor surgical outcome.

A study[16] in Sokoto reported a good visual outcome of 6/18 or better in 58% of pseudophakic eyes and increases to 69% with pin hole. Similar study[24] in same state reported poor outcome in 18% of pseudophakic eyes which reduces to 10% with pinhole correction. The improvement of visual outcomes in these studies was due to integration of primary eye care into the primary health care through legislation in the state, which is an eye care program based on the VISION 2020 Right to Sight strategy, and was implemented between 2005 and 2014 in Sokoto State, Nigeria, by the Ministry of Health in collaboration with Sight savers, international.

Studies in South Africa reported that 24.6% and Kenya 22% of eyes that had undergone cataract surgery had poor outcome respectively.[11],[28] Better patients selection for surgery and implementing a monitoring system for cataract surgical results could sensitise surgeons to quality control, thereby improving cataract surgical outcomes.


This study was conducted about 10 years after the national blindness survey in the country, and the results were low CSC with a relatively high couching coverage and poor visual outcome which did not differ significantly from the findings reported from the previous survey. In view of the above reason, there is a need to improve cataract surgical uptake by providing facilities and promoting practices and behaviour that are acceptable, accessible and affordable to patients. Advocacy to people and community leaders will also be helpful. Encourage monitoring of the outcome of surgery to improve quality, through training and re-training of ophthalmologists.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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