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ORIGINAL ARTICLE
Year : 2013  |  Volume : 5  |  Issue : 1  |  Page : 9-16

Rapid assessment of avoidable blindness in amran and lahj governorates of Yemen


1 Department of Ophthalmology, Faculty of Medicine and Health Sciences, Sana'a University; Department of Ophthalmology ,Al-Thawrah Modern General Hospital; Department of Ophthalmology ,Al- Kuwait University Hospital Sana'a, Sana'a, Yemen
2 Department of Ophthalmology, Faculty of Medicine and Health Sciences, Sana'a University; Department of Ophthalmology ,Al- Kuwait University Hospital Sana'a, Sana'a, Yemen
3 Department of Ophthalmology, Faculty of Medicine and Health Sciences, Sana'a University; Department of Ophthalmology ,Al-Thawrah Modern General Hospital, Sana'a, Yemen

Date of Web Publication21-Sep-2013

Correspondence Address:
Tawfik Kaid Al-Khatib
Sana'a University, Faculty of Medicine and Health Sciences; P.O. Box: 13264 Sana'a
Yemen
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DOI: 10.4103/1858-540X.118640

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  Abstract 

Objectives: To determine the magnitude and causes of avoidable blindness in 50 years and older population of Amran and Lahj governorates, Yemen. Materials and Methods: Using the RAAB manual, 78 clusters were randomly selected, 50 people aged of 50 ≥50 years were examined in each cluster. Visual acuity (VA) was measured with a tumbling "E" chart. Ophthalmologists examined people with <6/18 in either eye. A software program for RAAB was used for data collection and analysis. Results: In Amran and Lahj, 1789 (91.8%) and 1836 (94.3%) people were examined, respectively. The prevalence of blindness (VA < 3/60 in better eye, with available correction) in Amran was 9.33%, while in Lahj it was 10.84%. The principal cause of blindness was unoperated cataract in both governorates. The three main barriers to cataract surgery were unaware of treatment, destiny /God's will and cannot afford in both Amran and Lahj governorates. Conclusion: The prevalence of blindness, severe visual impairment and visual impairment in people aged ≥50 years in Amran and Lahj governorates were relatively higher than WHO's estimate in the sub region and the principal cause of blindness was untreated cataract in both governorates.

Keywords: Blindness, clusters, rapid assessments of avoidable blindness (RAAB), visual acuity, Yemen


How to cite this article:
Al-Khatib TK, Ahmed AA, Hameed AS. Rapid assessment of avoidable blindness in amran and lahj governorates of Yemen. Sudanese J Ophthalmol 2013;5:9-16

How to cite this URL:
Al-Khatib TK, Ahmed AA, Hameed AS. Rapid assessment of avoidable blindness in amran and lahj governorates of Yemen. Sudanese J Ophthalmol [serial online] 2013 [cited 2019 Jul 15];5:9-16. Available from: http://www.sjopthal.net/text.asp?2013/5/1/9/118640


  Introduction Top


Global estimates suggest that in 2002 there were more than 161 million people who were visually impaired (bilateral visual acuity [VA] <6/18 with best correction) of whom approximately 37 million were blind (bilateral VA <3/60). [1] Vision 2020: The Right to Sight is a global initiative that aims to eliminate avoidable blindness by the year 2020. It was launched in 1999 by the World Health Organization (WHO World Health Organisation ) and the International Agency for the Prevention of Blindness together with more than 20 international organizations. The priority disease in the first phase of Vision 2020 is cataract, refractive error and low vision, childhood blindness, onchocerciasis, and trachoma. These conditions constitute more that 75% of blinding diseases. Approximately 75-80% of all blindness is avoidable, this means that it can either be treated such as refractive error, cataract, and uncorrected aphakia, or prevented such trachoma, corneal scarring, childhood blindness, onchocerciasis, and to a certain extent glaucoma and diabetic retinopathy. [2]

Rapid assessment methods are means to undertake a comprehensive assessment of a public health issue using minimum resources within a limited amount of time. Such methods help plan, develop, and implement interventions and monitor service delivery. These methods are typically useful in situations where data are needed quickly and time and cost factors prohibit the use of classical research studies. [3] This requires a simple survey methodology, including a basic eye examination with standardized basic equipment, which can be used by locally available ophthalmic staff.

The expected prevalence of avoidable blindness in people of 50 years and older for different WHO sub-regions ranges from 0.4 %to 9% [4] (7% in Yemen). A local study in Hethransub-district of Taiz in Yemen in 2002 showed a prevalence of 7.9%. [5]

The aim of study was to assess the magnitude of blindness and the principle cause of blindness in people aged 50 years and above in Amran and Lahj governorates in Yemen, and to evaluate the availability and quality of the cataract surgical services.


  Materials and Methods Top


Rapid Assessments of Avoidable blindness (RAAB) methodology was used to survey two governorates in Yemen, namely, Amran and Lahj governorates. The two governorates were identified to represent the whole country. The total population of Yemen is less than 5 million according to the 2007 census. [6] Amran governorate is in the north and localized on a mountainous area with 800 000 population and Lahj is in the south and localized on the sea, with a population of 784 412.

Sample Size

Assuming that

  • All adults aged ≥50 years in Amran (74.818) and Lahj (72.613),
  • Design effect =1.5,
  • Expected prevalence of blindness in Yemen for people aged ≥50 years = 7.5%,
  • Confidence interval = 95% and
  • Non response = 10%,


The required sample size is 1948 in Amran and 1948 in Lahj calculated using the formulas provided by: Bennett. S; woods T, Lyanoge WM. [6] A total 39 cluster of 50 adults aged ≥50 years were required for this survey in Amran governorate and 39 clusters of 50 persons aged ≥50 years in Lahj. The fieldwork was carried out in April 2009 in Amran and in May 2009 in Lahj.

Sample Frame

The clusters were selected with probability - proportionate to size - separately for Amran and Lahj, using updated data from the census in 2007 as the sampling frame. Households within clusters were selected through compact segment sampling, maps of the enumeration area showing major landmarks and the approximate distribution of households were obtained or drown. [7] The enumeration area was then divided into segments, each including approximately 50 people aged ≥ 50 years, and one segment was selected at random by drawing lots.

The survey team then visited all the households in that segment, door to door, until 50 people aged ≥50 years were identified. If the target number of 50 people aged ≥ 50 years was not reached, another segment was chosen at random and sampling continued. If an eligible household member was absent, at least two return visits were made. Information about visual status was ascertained from relatives or neighbors for people who were not available after repeated visits and also for refusals and those with communication difficulties.

Ophthalmic Examination

Historical events were used to identify the age of the respondents. Individuals aged 50 years and above and resident in the cluster continuously for the past six months were eligible for inclusion. Informed verbal consent was obtained from each eligible individual, in the presence of a local witness and examination was only undertaken after consent was obtained for supplementing ethical issues in accordance with Helsinki declaration for international guidelines for biomedical research involving human subjects, issued in 1992.

Visual acuity (VA) was measured with a tumbling "E" chart with a snellen optotype size 6/60 (20/200) on one side and size 6/18 (20/60) on the other side at a distance of 6 or 3 or 1 m land marked on the rope. The results first of the right eye and then of left eye were recorded in the RAAB survey form.

Pinhole vision was measured if the VA was less than 6/18 in either eye. All measurements were taken in full daylight and people were categorized according to VA and visual field with available correction (WHO) as follows.

  • Blind: VA <3/60 with best correction in the better eye or visual field of 10 degrees or less around visual axis.
  • Severely visually impaired: VA <6/60 but ≥3/60 with best correction in the better eye or visual field of 20 degrees or less, but more than 10 degrees.
  • Visually impaired: VA <6/18 but ≥6/60 with best correction in the better eye or visual field of 30 degrees or less, but more than 20 degrees.


Persons who failed to see 6/18 optotype at 6 m and not improved with the pinhole in any eye were further examined by an ophthalmologist. If the cause was not cataract the eye should be dilated to find the principal cause of blindness. Ophthalmologist using a torch and direct ophthalmoscope in a shaded or dark environment without dilating the pupil assessed the lens status of all individuals.

The following case definitions were used for identifying the cause of visual impairment:

Cataract: Presence of a visible cataract impairing vision.

Refractive error: Vision <6/18 improving to >6/18 with pinhole.

Glaucoma: In the absence of any other obvious cause, the presence of significant pallor and cup: Disc ratio >0.6 along with pigmentary changes and other sings of glaucoma including evidence of iridectomy / blebs etc and C:D asymmetry >0.2 between the two eyes.

Diabetic Retinopathy as the Cause of Visual Impairment when:

  • There were more than 5 mm aneurysms.
  • Clinically significant macular edema (CSME) on a distant direct ophthalmoscope.
  • Neo vascularization of the disc/Neo vascularization elsewhere (NVD/NVE)
  • Vitreous hemorrhage suspected, Age related macular degeneration (ARMD) was marked as the cause of visual impairment (VI) when:
    • There was drusen at macula.
    • Macular scar was present.
    • "Wet" ARMD was recorded.
    • Geographic atrophy was observed.


Training

There were five teams; each team was made up of one ophthalmologist, one ophthalmic nurse, and one local health worker. All participants had 1 week training on RAAB survey at the ministry of health, Sana'a, supervised by the National Coordinator of Prevention of Blindness and WHO ophthalmoepidemiologist from Pakistan. The training was in the form of lectures, practical training in Al-Thawrah hospital, Sana'a and a pilot work in Hamal village out of Sana'a. One team was to cover one cluster every day. The interobserve agreement for measurement of VA, lens examination, and cause of blindness was assessed between the teams to ensure that it was acceptable by kappa statistic standard (i.e., kappa ≥ 0.60).

One RAAB took 25 days of fieldwork and training; it was relatively cheap and easy to conduct. Compact segment sampling was used to select households within clusters, which is preferable to the random walk method, since there is less subjectivity in the section of households [8] and has a higher precision and lower risk of bias. [9]

Statistical Analysis

A software program developed for this survey (RAAB V. 3.1 developed in Epi-Info 6.04d using the windows interface provided by Epi Data Version.3.1 {Centers for Disease Control and Prevention} and Epi - Info Version 3.3.2) was used for data entry and automatic standardized data analysis. The prevalence estimates took account of the design effect (DEFF) when estimating the confidence intervals (CIs) calculated in sample module of Epi - Info Version 6.04b.

The cataract surgical coverage of people, or the proportion of people needing surgery or who had undergone cataract surgery, was calculated by dividing the number of cataract surgeries (number of people with bilateral pseudophakia or aphakia plus the number of people with unilateral pseudophakia or aphakia and unilateral visual impairment) by the sum of the number of surgeries plus the number of people visually impaired from cataract. Cataract surgical coverage was also calculated for eyes. As VA before surgery was not known we assumed, in turn, that only patients with VA below a certain threshold (< 3/60, <6/60 AND < 6/18) received surgery for their cataract.

Ethical Approval

The Ministry of Public Health and Population granted ethical approval for this work in addition to administrative heads of Amran and Lahj governorates. Informed verbal consent was obtained from all people after explanation of the nature and possible consequences of the study. All people with operable cataract or other treatable conditions were referred for free treatment.


  Results Top


In Amran, the sample selected included 1948 persons, of whom 1789 (91.8%) were examined, 63 (3.2%) were not available, 71 (3.6%) refused to be examined and 25 (1.3%) were not capable for examination. In Lahj, the sample selected included 1948 persons, of whom 1836 (94.3%) were examined and 58 (3.0%) were not available, 37 (1.9%) refused to be examined, and 17 (0.9%) were not capable for examination.

In Amran, males were 1014 (52.1%) and females were 934 (47.9%) in number. In Lahj, males were 1018 (52.1%) and females were 930 (47.7%) in number. An average age of the sample population was 64.5 years in Amran and 63.4 years in Lahj.

The sampled population was relatively representative of the governorates population in terms of age and sex distribution [Table 1]a and 1b.
Table 1:

Click here to view


In Amran, there were 167 bilaterally blind people with available correction in people aged ≥ 50 years giving a sample prevalence of bilateral blindness of 9.33 % (95%CI = 7.41-11.26) with observed DEFF of 2.04, and there were 158 bilaterally blind people with best correction or pinhole in the better eye giving a sample prevalence of bilateral blindness of 8.83% (95%CI = 6.96-10.71) with observed DEFF of 2.03.

In Lahj, there were 199 bilaterally blind people with available correction giving a sample prevalence (presenting VA) in people aged ≥ 50 years was 10.84% (95%CI = 8.69-12.98; DEFF 2.28) which is more than in Amran, and there were 192 bilaterally blind people with best correction or pinhole in the better eye giving a sample prevalence of bilateral blindness 10.46% (95%CI = 8.24-12.67; DEFF 2.51) which is more than Amran governorate.

In both areas, the prevalence of blindness was higher in women (9.98% in Amran and 11.54% in Lahj) than in men (7.84% in Amran and 9.51% in Lahj) [Table 2]a and 1b.
Table 2:

Click here to view


The prevalence of blindness and severe visual impairment and visual impairment rapidly increased with the age.

Extrapolating survey data to the age and sex distribution from census, in people aged ≥50 years, in Amran, there are an estimated 4961 (6.63%) cases of bilateral blindness and 2311 (3.09%) cases of bilateral severe visual impairment and 9401 (12.26%) cases of bilateral visual impairment, while in Lahj, the estimated bilateral blindness 6.967 (9.60%) cases and 4.449 (6.13%) cases of bilateral severe visual impairment and 9850 (13.57%) cases of bilateral visual impairment, the prevalence of blindness in Lahj is higher than in Amran [Table 3]a and 3b.
Table 3:

Click here to view


The principle cause of blindness, severe visual impairment, and visual impairment in people with available correction was untreated cataract in both Amran and Lahj. ARMD was the second cause of blindness in Amran being 7.8% while Glaucoma was the second cause of blindness in Lahj. Refractive errors comes the second cause of visual impairment in both Amran and Lahj [Table 4].
Table 4: Causes of blindness, severs visual impairment and visual impairment in people with available correction in Amran and Lahj governorates

Click here to view


The three main barriers to cataract surgery in Amran and Lahj were unawareness of treatment, destiny/God's will, and cannot afford. The fourth barrier in Amran was how to get surgery and in Lahj the surgery is contraindicated. The fifth barrier in Amran was waiting for maturity and in Lahj two barriers no company and no need due to old age [Table 5]a and b.
Table 5:

Click here to view


The visual acuity after cataract surgery was poor in Lahj (cannot see 6/60) 42.07% in comparison to Amran 30.5% [Table 6]a and 6b.
Table 6:

Click here to view


The cataract surgical coverage in Amran was VA< 3/60 in 50.7%, VA <6/60 in 45.4% and VA < 6/18 in 35.2%, while in Lahj was VA<3/60 in 64.7%, VA <6/60 in 58.0% and VA <6/18 in 47.1% [Table 7]a and 7b.
Table 7:

Click here to view



  Discussion Top


The prevalence of bilateral blindness based on best corrected vision in the better eye in Amran was 8.8% and based on presenting vision in the better eye was 9.3%. In Lahj, it was 10.5% and 10.8%, respectively. These figures are within the upper estimation or exceeding the estimate of the WHO sub-region (0.4-9.0%) [1] and a previous local study. [5] Also it looks higher than other studies as in Philippines (2.6%), in Negros Island (2.4-3.6 %), [10] in Antique district in Bangladesh (2.9%), [11] and in India (3.6%). [12] Our results are also high compared to the results of African countries such as Kenya (Nakura district) where prevalence was 2.0% [13] and in western Rwanda where prevalence was 1.8%. [14]

The prevalence of bilateral severe visual impairment in Amran was 3.86% (95%CI=2.85-4.86%) in better eye with available correction, while in Lahj it was 6.43% (95%CI=5.08-7.78%), which is more than Amran. The prevalence of visual impairment in Amran was 14.42% (95%CI = 12.43-16.41; DEFF 1.49) in better eye with available correction, while in Lahj it was 15.44% (95%CI = 12.62-16.03%; DEFF 1.14).

The vast majority of blindness and severe visual impairment was due to untreated cataract while both cataract and refractive errors were responsible for most of the visual impairment in Amran and Lahj. Most of the causes of blindness were avoidable in both governorates (79.6% and 84.9%). Causes were untreated cataract, surgical complications, corneal scarring, uncorrected aphakia, phthisis, and refractive errors. There were no cases of trachoma or onchocerciasis in both governorates. The estimates of prevalence of blindness, severe visual impairment, and visual impairment were more in Lahj than in Amran, the reason for that being proximity of Amran to Sana'a (Capital of Yemen) giving better accessibility to ophthalmic services in Sana'a.

The majority of blindness and severe visual impairment was due to cataract in Amran and Lahj.

The cataract surgical coverage was low in Amran and moderate in Lahj. Improving access to cataract surgical services should be a priority in the rural areas of Lahj and Amran.

The three main barriers to cataract surgery in both governorates were unawareness of treatment, destiny/God's will. To minimize these barriers, many factors should be considered like health education and provision of accessible and affordable ophthalmic services in all districts of the country.

The quality of cataract surgery was a concern, and implementing and maintaining a system for cataract surgery auditing could sensitizes surgeons to quality control and improve outcomes after surgery.

Refractive errors were the second cause of visual impairment after cataract showing that more optometry services are needed. We can also assume that almost all of the people aged ≥50 years will need presbyopic glasses. The posterior segment disorders are important contributors to blindness and severe visual impairment supporting other findings of concern for prevention of blindness. [2] The cause of posterior segment disorders could not be diagnosed accurately in this door to door survey. Surgical complications, corneal scarring and phthisis were among the causes of blindness in this study.


  Conclusion Top


The prevalence of blindness, severe visual impairment, and visual impairment in people aged ≥50 years in Amran and Lahj governorates of Yemen were relatively higher than WHO estimates for the sub-region. The majority of blindness and visual impairment was due to curable (treatable) causes, through cataract surgery, and distributing spectacles. The cataract surgical rate is insufficient to meet current need and attention needs to be paid to improve outcome after surgery through improving the ophthalmic services in both governorates. More collaboration and involvement of governmental and non-governmental organizations is needed.


  Acknowledgments Top


We would like to express thanks for the technical and financial support given by the WHO Sana'a office and the WHO EMRO expert Dr Abdul Hannan Chaudhury who participated in the RAAB training workshop and for his valuable instructions and support. Many thanks go to Dr Zahid Jadoon who trained the teams in the workshop and continuously helped us in any difficulty. We would like also to thank all those who took part in the surveys, local communities and local rural health teams.

 
  References Top

1.Limburg H, Kumar R, Indrayan A, Sundaeram KR. Rapid assessment of prevalence of cataract blindness as District level. Int J Epidermal 1997;26:1049-54.  Back to cited text no. 1
    
2.Hans Lim burg, Meester W, Kuper H, Polack S. RAAB Instruction Manual, International Center for Eye Health, 2007;Version 4.02 : 3-6   Back to cited text no. 2
    
3.Marmamula S, Keeffe J, Khanna R, Rao G N. Rapid assessment methods in eye care and their use in assessing refractive errors. J Comm Eye Health 2007;20:95-7.  Back to cited text no. 3
    
4.Resnikoff S, Pascolini D, Etya'ale D, Kocur I, Pararajasegaram R, Pokharel GP, et al. Global data on visual impairment in the year 2002. Bull World Health Organ 2004;82:844-51.   Back to cited text no. 4
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5.Al-Mohammadi K. Prevalence of low vision and Blindness in Age Group 50 years and above in Hethran Sub district, Taiz, Yemen, a Fulfillment for Master degree in Community Ophthalmology, PICO, Peshawar, Pakistan, 2002.  Back to cited text no. 5
    
6.Census Planning, 2007 Census of Population and Housing, Sana'a Yemen. National Statistics Office, 2007.  Back to cited text no. 6
    
7.Bennett S, Woods T, Liyanage WM, Smith DL. A Simplified general method for cluster sample surveys of Health in developing countries. World Health Stat Q 1991;44:98-106.   Back to cited text no. 7
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8.Milligan P, Njie A, Bennett S. comparison of two cluster Sampling methods for health surveys in developing countries. Int J Epidemiol 2004;33:469-76.   Back to cited text no. 8
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9.Turner AG, Magnani RJ, Shuaib M. A not quite as quick but much cleaner alternative to the expanded programme on immunization (epi) cluster survey design. Int J Epidemiol 1996;25:198-203.   Back to cited text no. 9
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10.Eusebio C, Kuper H, Polack S, Enconado J, Tongson N, Dionio D, et al. Rapid assessment of avoidable blindness in Negros Island and Antique district. Br J Ophthalmol 2007;91:1588-92.   Back to cited text no. 10
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11.Wadud Z, Kuper H, Polack S, Lindfield R, Akm MR, Choudhury KA, et al. Rapid assessment of avoidable blindness and need assessment of cataract surgical services in Satkhira district, Bangladesh. Br J Ophthalmol 2006;90:1225-9.   Back to cited text no. 11
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12.Neena J, Rachel J, Praveen V, Muthy GV. Rapid assessment of avoidable Blindness in India. PLoS One 2008;3:e 2867.  Back to cited text no. 12
    
13.Mathenge W, Kuper H, Limburg H, Polack S, Onyango O, Nyaga G, et al. Rapid assessment of avoidable blindness in Nakuru district, Kenya. Ophthalmology 2007;114:599-605.   Back to cited text no. 13
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14.Mathenge W, Nkurikiye J, Limburg H, Kuper H. Rapid Assessment of Avoidable Blindness in Western Rawanda: Blindness in a postconflict Setting. PLoS Med 2007;4:e217.  Back to cited text no. 14
[PUBMED]    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]


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