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Prevalence of blindness and cataract surgical coverage in Narayani Zone, Nepal: a rapid assessment of avoidable blindness (RAAB) study
  1. Sangita Pradhan1,
  2. Avnish Deshmukh1,
  3. Puspa Giri Shrestha1,
  4. Prajwal Basnet2,
  5. Ram Prasad Kandel3,
  6. Susan Lewallen4,
  7. Yuddha Dhoj Sapkota5,
  8. Ken Bassett6,7,
  9. Vivian T Yin6,7
  1. 1 Bharatpur Eye Hospital, Bharatpur, Narayani, Nepal
  2. 2 Gaur Eye Hospital, Purenwa, Nepal
  3. 3 Seva Nepal, Kathmandu, Nepal
  4. 4 Kilimanjaro Centre for Community Ophthalmology, University Cape Town Groot Schuur Hospital, Cape Town, South Africa
  5. 5 Nepal Netra Jyoti Sangh, Kathmandu, Nepal
  6. 6 British Columbia Centre for Epidemiologic and International Ophthalmology, University of British Columbia, Vancouver, Canada
  7. 7 Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada
  1. Correspondence to Dr Vivian T Yin, Eye Care Center, Vancouver General Hospital, 2550 Willow St, Vancouver, BC V5Z 3N9, Canada; viviany{at}me.com

Abstract

Background The 1981 Nepal Blindness Survey first identified the Narayani Zone as one of the regions with the highest prevalence of blindness in the country. Subseuqently, a 2006 survey of the Rautahat District of the Narayani Zone found it to have the country’s highest blindness prevalence. This study examines the impact on blind avoidable and treatable eye conditions in this region after significant increase in eye care services in the past decade.

Methods The rapid assessment of avoidable blindness (RAAB) methodology was used with mobile data collection using the mRAAB smartphone app. Data analysis was done using the standard RAAB software. Based on the 2011 census, 100 clusters of 50 participants aged 50 years or older were randomly sampled proportional to population size.

Results Of the 5000 participants surveyed, 4771 (95.4%) were examined. The age-adjusted and sex-adjusted prevalence of bilateral blindness, severe visual impairment (SVI) and moderate visual impairment (MVI) were 1.2% (95% CI 0.9% to 1.5%), 2.5% (95% CI 2.0% to -3.0%) and 13.2% (95% CI 11.8% to 14.5%), respectively. Cataract remains the primary cause of blindness and SVI despite cataract surgery coverage (CSC) of 91.5% for VA<3/60. Women still account for two-thirds of blindness.

Conclusion The prevalence of blindness in people over the age of 50 years has decreased from 6.9% in 2006 to 1.2%, a level in keeping with the national average; however, significant gender inequity persists. CSC has improved but continues to favour men.

  • epidemiology
  • public health

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Introduction

The Nepal Blindness Survey (1981) showed a national prevalence of blindness (<3/60) of 0.84% for all ages, and 8.58% for people over age 60 years.1 Cataract was the leading cause of blindness with uneven distribution by terrain and sex.1 The prevalence of cataract was significantly higher in the low altitude plains bordering India (4.17%) than the hill (1.81%) and mountainous regions (1.86%) (OR of 1.51).1 The Narayani Zone included the central plains region, which had the country’s highest cataract prevalence (4.5%).1

A blindness survey conducted in the Rautahaat District of Narayani Zone in 2006 of people over age 50 years reported a blindness prevalence of 6.9%.2 The weighted average of blindness in Nepal was estimated as 2.1% (1.9% male, 2.3% female).3

Following a significant increase in hospital and community eye care services in the past decade, local eye care leaders in Narayani Zone sought evidence of their impact on avoidable and treatable blinding conditions in their region.

Methods

This is a population-based survey using the rapid assessment of preventable blindness (RAAB) methodology.4 According to the 2011 census, the population of Narayani Zone was 2.99 million (1.51 million male and 1.48 million female) with 12% of the population aged 50 years and older. The sample size was calculated using the RAAB software (RAAB V. 5, International Centre for Eye Health, London, UK) assuming a conservative estimate of the prevalence of blindness at 2.3% from a 2006 survey involving the Chitwan District of Narayani Zone.3 Rounding up to the nearest 1000 people, the sample size was calculated to be 5000 with precision of 20%, 90% examined response rate and a cluster design effect of 1.5. As per the Wrold Health Organization, blindness is defined as presenting visual acuity (VA) in the better eye of less than 3/60, severe visual impairment (SVI) is VA of 3/60 or better and less than 6/60 and moderate visual impairment (MVI) is VA of 6/60 or better and less than 6/18.

Cataract surgical coverage (CSC), an estimate of the extend of which a population’s cataract surgery needs has been met, is calculated by the proportion of number of people with operated cataract as a proportion of total estimated operable cataract. Cataract surgical outcome is the final visual outcome of patients who have undergone cataract surgery, divided into three categories: good (6/18 or better), fair (6/60 or better) or poor (worse than 6/60).

Sampling methodology

In the 2011 Nepal National Census, the smallest population unit enumerated was the Ward. There are 3276 Wards in the Narayani Zone, varying in population from 16 to 21 844. Wards with more than 800 people were further segmented, while Wards with small populations were joined to make up study cluster size of approximately 800 people. One hundred clusters were selected by systematic random sampling proportional to size using the RAAB software. In each study cluster, 50 people aged ≥50 years were selected by compact segment sampling. Three clinical teams, consisting of an ophthalmologist, an ophthalmic assistant, a driver and a local female community health worker were trained by ICEH-certified RAAB trainer and obtained interobserver concordance of 0.8, as the standard set out by the RAAB protocol.

A letter of introduction describing activities was sent to the community leaders of towns and villages prior to the visit. Necessary permission from the appropriate health authorities was obtained. Verbal consent was obtained from all participants prior to examination. The study had ethic approval from Nepal Health Research Council (Reg. No. 255/2015). Data were entered into the mRAAB software and emailed to the study coordinator daily. The data files were imported into the RAAB5 software and analysed for standard RAAB findings. Furthermore, the data were segregated into the hills (Chitwan and Makawanpur districts) and plains (Bara, Paras and Rautahat districts) and analysed separately.

Results

Of 5000 people surveyed, 4771 (95.4%) were examined, male 2270 (47.5%) and female 2501 (52.5%). Of the 229 participants not examined, 162 (3.2%) were not available, 23 (0.5%) refused examination and in 44 (0.9%) participants’ examination was not capable.

The age-adjusted and sex-adjusted prevalence of blindness, SVI and MVI were 1.2% (95% CI 0.9% to 1.5%), 2.5% (95% CI 2.0% to 3.0%) and 13.2% (95% CI11.8% to 14.5%), respectively (table 1). The prevalence of blindness, but not SVI or MVI, was higher in women (1.7% (95% CI 1.1% to 2.3%)) than in men (0.8% (95% CI 0.4% to 1.1%)) (table 1). The most common cause of blindness and SVI was untreated cataract, accounting for 61.8% and 78.5%, respectively (table 2). The most common cause of MVI was uncorrected refractive error at 67.0% followed by untreated cataract at 27.5%. Over 90% of the blindness, SVI and MVI were avoidable, including treatable and preventable causes (table 2).

Table 1

Age-adjusted and sex-adjusted prevalence of bilateral blindness, SVI and MVI with presenting visual acuity

Table 2

Causes of blindness, SVI and MVI

The prevalence of cataract blindness was 0.6% (95% CI 0.4% to 0.9%) with female prevalence (1.0% (95% CI 0.5% to 1.4%)), not significantly higher than male (0.3% (95% CI 0.1% to 0.6%)). The prevalence of cataract MVI was significantly higher for women (4.5% (95% CI 3.8% to 5.3%)) compared with men 2.6% (95% CI 1.9% to 3.4%) (table 3).

Table 3

Age-adjusted and sex-adjusted prevalence of cataract bilateral blindness, SVI and MVI with presenting visual acuity

The most frequently reported barriers to surgery in patients with cataract SVI were ‘need not felt’ (49.5%) followed by cost (27.5%) and fear (13.8%). Cost was a more common barrier to cataract surgery reported by women (32.3%) compared with men (21.3%) (table 4).

Table 4

Barriers to cataract surgery in patients with bilateral best corrected visual acuity <6/60 due to cataracts

Cataract surgical coverage (CSC) for VA <3/60 was 91.5% (male 94.7%, female 89.3%). CSC for VA <6/60 and <6/18 were 80.6% and 61.4%, respectively, with very similar proportions for men and women (table 5). The surgical outcome was 72.1%, 20.1% and 7.8% for VA >6/18 (good outcome), 6/60 to 6/18 (borderline outcome) and <6/60 (poor outcome), respectively. Intraocular lens implantation accounted for 97% of cataract surgery. Cataract surgery was performed at charity (88.2%) followed by government (7.2%) and private (2.6%) hospitals, and a small number at transient outreach eye ‘camps’ in remote regions (1.9%) (data not shown). The leading cause of borderline surgical outcome was the need for spectacles (64.6%), whereas for poor surgical outcome it was due to poor patient selection (37.7%), where there may have been posterior pole disease limiting visual outcome, and long-term sequelae of surgery (37.7%) such as retinal detachment.

Table 5

Age-adjusted and sex-adjusted cataract surgical coverage for each person in percentage

Hills versus plains

Similar age-adjusted and sex-adjusted prevalence of blindness of 1.2% was found in both the hills and plains. However, SVI and MVI were both significantly higher in the plains versus the hills: SVI was 3.1% (95% CI 2.5% to 3.7%) and 1.3% (95% CI 0.6% to 2.0%) for plains and hills, respectively; MVI was 14.2% (95% CI 12.5% to 15.8%) and 10.7% (95% CI 8.7% to 12.6%) for plains and hills, respectively.

The CSC (VA<3/60) was slightly higher in the plains (92.9%) compared with the hills (88.2%). CSC (VA<3/60) was lower for women (90%) than men (97%) in the plains and similar in the hills (women 87.9%, men 88.5%). In contrast, the CSC for VA<6/60 was similar for men and women in the plains and hills (data not shown).

The leading barriers to cataract surgery for bilateral VA <6/60 were ‘need not felt’ (63.8%) and cost (26.3%) for the plains, but fear (35.7%) and cost (32.1%) for the hills. Good outcome of cataract surgery (can see 6/18) was similar for plains (73.4%) and hills (68.5%), respectively.

Discussion

Compared with the survey of Chitwan District of Narayani Zone in 2006,5 this survey of the entire Narayani Zone found a significant decrease in the prevalence of blindness from 2.3% to 1.2%. However, the prevalence of SVI remained the same, 2.5% in this survey compared with 2.3% in 2006. The reduction in the estimate for overall blindness in Narayani Zone compared with Chitwan District is encouraging given that the Chitwan District is known to have the most active community-based programme serving the Nepali population and assumed to have lowest prevalence of blindness. A reduction in overall prevalence compared with the Chitwan standard is encouraging. Cataract continues to be the leading cause of blindness and SVI and second leading cause of MVI.

Compared with the survey of Rautahat District of Naryani Zone in 2006,2 this survey of the entire Narayani Zone found an even larger decrease in the prevalence of blindness from 6.9% to 1.2% and a decrease in SVI from 10.5% to 2.5% and MVI from 24.3% to 13.2%. Rautahat, in contrast to Chitwan, District was found to have the highest prevalence of blindness, SVI and MVI in the country.3

Women accounted for 67.8% of blindness (women 1.7%, men 0.8%) and cataract blindness (women 1.0%, men 0.3%) in this study. In 2001, Abou-Gareeb et al 6 first showed that women account for 64.5% of all blind people in Asia, Africa and industrialised countries, with almost all the inequity due to decreased utilisation of services by women. Since 2002, hospitals in the Lumbini Zone and Chitwan District have developed community-based programme to increase women’s awareness and utilisation of available services.7 These efforts led to a decrease in the prevalence of blindness among women compared with men in Lumbini Zone and Chitwan District of Narayani Zone, the only places achieving this equity in Nepal.5 However, the remainder of Narayani Zone outside Chitwan District did not implement these programme, likely resulting in the gender inequity in the current survey, similar to the remainder of Nepal.3

The visual outcome of cataract surgery (presenting VA 6/18 or better) improved substantially in this survey of the entire Narayani Zone (72.1%) compared with the 2006 Chitwan (23.7%)8 and Rautahat District surveys (40.0%).2 Although only two districts were surveyed in 2006, it seems reasonable to assume that surgical quality has improved significantly in the Narayani Zone in the past decade. Among the patients with intraocular lens implantation, presenting VA 6/18 or better was 72.1% in this survey compared with 47.2% in the 2006 Chitwan survey (and 56.6% in the Rautahat survey). The improved visual outcome of cataract surgery likely increased acceptance, which led to the higher CSC in the Narayani Zone. However, there is clearly more room for improvement in better refractive outcome or postoperative refraction for glasses and patient selection in order to achieve the goal of 80% having 6/18 or better presenting vision.

In this survey, the prevalence of blindness was similar (both 1.2%) in the plain and hill areas, in contrast to the 2006 Lumbini and Chitwan survey that found the plains had significantly higher blindness prevalence (5.8% and 3.3% for plains and hills, respectively, OR 0.6 (CI 0.4 to 0.9)).5 The similar blindness prevalence in plains and hills in this study likely reflects the increase in CSC (VA<3/60) in the plains areas from 68% to 93%.

The prevalence of SVI and MVI, in contrast to blindness, both remain significantly higher in the plains versus hills. This likely reflects both higher prevalence and lower coverage in the plains and insufficient CSC for people with SVI and MVI. Dealing with the eye care needs of the Nepali population in the plain regions remains a challenge for eye programme located near and primarily serving Indian patients who cross the border seeking the higher quality care and are willing to pay for services.

The barriers to cataract surgery in patients with blindness or SVI were different between the plains and hills with ‘need not felt’ as the leading barrier in the plains (63.8%) compared with fear (35.7%) and cost (32.1%) in the hills. This difference in perceived ‘need for surgery’ may account for the insufficient CSC for people with SVI and MVI in the plains. The difference in barriers to cataract surgery between the plains and hills also highlights the need for customised programme in improving access to care overall.

In conclusion, the prevalence of blindness and cataract blindness decreased significantly in Narayani Zone, Nepal from 2006 to 2016. Cataract remains the leading cause of blindness and SVI despite the substantial increase in CSC. Cataract surgical outcome also improved dramatically but has not yet reached WHO recommended standards largely due to need for spectacles after surgery. Gender inequity persists in the Narayani Zone despite the progress reported previously in Chitwan District.

References

Footnotes

  • Contributors All authors have substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data. The authors draft the work or revised it critically for important intellectual content and gave final approval of the version published. The authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Nepal Health Research Proposal.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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