Elsevier

Ophthalmology

Volume 114, Issue 3, March 2007, Pages 599-605
Ophthalmology

Original Article
Rapid Assessment of Avoidable Blindness in Nakuru District, Kenya

https://doi.org/10.1016/j.ophtha.2006.06.057Get rights and content

Objectives

To estimate the prevalence of avoidable blindness in ≥50-year-olds in Nakuru district, Kenya, and to evaluate the Rapid Assessment for Avoidable Blindness (RAAB), a new methodology to measure the magnitude and causes of blindness.

Design

Cross-sectional population-based survey.

Participants

Seventy-six clusters of 50 people 50 years or older were selected by probability proportionate to size sampling of clusters. Households within clusters were selected through compact segment sampling. Three thousand seven hundred eighty-four eligible subjects were selected, of whom 3503 (92.6%) were examined.

Methods

Participants underwent a comprehensive ophthalmic examination in their homes by an ophthalmologist, including measurement of visual acuity (VA) with a tumbling-E chart and the diagnosis of the principal cause of visual impairment. Those who had undergone cataract surgery were questioned about the details of the operation and their satisfaction with surgery. Those who were visually impaired from cataract were asked why they had not gone for surgery.

Main Outcome Measures

Visual acuity and principal cause of VA<6/18.

Results

The prevalence of bilateral blindness (presenting VA < 3/60) was 2.0% (95% confidence interval [CI], 1.5%–2.4%), and prevalence of bilateral visual impairment (VA of <6/18–≥6/60) was 5.8% (95% CI, 4.8%–6.8%) in the sample. Definite avoidable causes of blindness (i.e., cataract, refractive error, trachoma, and corneal scarring) were responsible for 69.6% of bilateral blindness and 74.9% of bilateral visual impairment. Cataract was the major cause of blindness (42.0%) and visual impairment (36.0%). The cataract surgical coverage was high, with 78% of those with bilateral cataract who needed surgery having had surgery at VA<3/60. The quality of surgery was of concern because 22% of the 222 eyes that had undergone cataract surgery had VA<6/60 with best correction. The main barriers to surgery were lack of awareness and cost. The RAAB methodology was easy to use, and each team could visit one cluster per day.

Conclusions

The prevalence of blindness in ≥50-year-olds in Nakuru district was low, in part due to the high cataract surgical coverage. The RAAB is easy to use and inexpensive and provides information about the magnitude and causes of avoidable blindness that can be used for planning and monitoring eye care services.

Section snippets

Sample Selection

The expected prevalence of blindness in ≥50-year-olds was estimated conservatively at 4.5%.1, 10, 11 Allowing for a required confidence of 95%, precision of 20% (i.e., worst acceptable result of 3.6%), population size of 88 700 people 50 or older in Nakuru,12 expected design effect of 1.7 for clusters of 50 based on data from the RACSS,2 and 10% nonresponse, the required sample size was estimated to be 3725 subjects (Epi Info 6.04, Centers for Disease Control and Prevention, Atlanta, GA). In

Results

The study population consisted of 3784 people. Two hundred twenty-two (5.9%) were not available, and 59 (1.6%) refused to be examined, so 3503 were included in the survey (92.6%). There was no difference in mean ages of those who were unavailable (61.3 years), those who refused (61.0), and those who were included (62.3), but those who refused were more likely to be female (66.1% of refusers vs. 46.9% of those unavailable and 52.4% of those examined). Of the 222 who were not available, 2 were

Avoidable Blindness

Vision 2020: The Right to Sight was launched in 1999 with the goal of eliminating avoidable blindness by 2020. The concept of avoidable blindness combines those diseases that are either easily preventable or treatable. The RACSS has been used and reported by several countries.2, 3, 4, 5, 6, 7, 8 The RACSS methodology has been adapted and used for the first time in this survey to assess the prevalence of avoidable blindness, not only cataract, using new data entry and analysis tools.

Experience with Rapid Assessment of Avoidable Blindness and Sampling

Compact

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  • Cited by (0)

    Manuscript no. 2005-1211.

    Supported by grants from the Christian Blind Mission, Bensheim, Germany; Sight Savers International, Haywards Heath, United Kingdom; and ORBIS International, London, United Kingdom.

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