Gender differences in blindness, cataract blindness and cataract surgical coverage in India: a systematic review and meta-analysis

Methodological quality of the review: Low confidence

 Author: Prasad M, Malhotra S, Kalaivani M, Vashist P, Gupta SK.

Region: India

Sector: Epidemiology

Subsector: Prevalance

Equity focus: Gender

Review type: Other review

Quantitative synthesis method: narrative synthesis and meta-analysis

Qualitative synthesis method: Not applicable

Background:
The magnitude of blindness is unevenly distributed worldwide and low and middle income countries (LMICs) bear the greater proportion of this burden. Moreover, 81% of people who are blind or have moderate or severe vision impairment are aged more than 50 years. The gender difference in cases of blindness in India may be due to inequity of access to and uptake of surgeries

Objectives:
To investigate gender differences in the prevalence of blindness, cataract blindness and cataract surgical coverage (CSC).

Main findings:
Authors included a total of 22 publications, which included 17 published studies and five reports. The number of studies included in the meta-analysis of WHO definition of blindness from rapid surveys was 10 for the outcome ‘blindness’, five for ‘cataract blindness’ and four for ‘cataract surgical coverage’.

The majority of the studies had been conducted in Southern India, and most study areas were rural. The mean age of study participants ranged from 61 to 70 years. The response rate was satisfactory in most of the studies that reported it.

In terms of risk of bias, authors noted that all except for two studies mentioned a sampling methodology that allowed for low risk of selection bias. In addition, apart from four studies, all reported a satisfactory response rate ranging from 80.2% to 99.7%. CIs for estimates were mentioned by all published studies except for two; and authors found that only one published report mentioned the CI along with the point estimate.

When authors analysed the data, they found the odds of blindness and cataract blindness were significantly higher among women compared with men: women had 35% higher odds of being blind (OR 1.35, 95% CI 1.08 to 1.62) and 69% higher odds of being cataract blind (OR 1.69, 95% CI 1.44 to 1.95). In addition, authors also found that women had 27% lower odds of going through cataract surgery (OR 0.73, 95% CI 0.45 to 1.01).

Authors pooled that prevalence of blindness among men was 4.17% and for women it was 5.68% (I² = 99.7%). In addition, the pooled prevalence for of cataract blindness among men was 3.92% and for women it was 6.13% (I²= 99.7%). The pooled CSC for men was 59.29% and for women it was 52.34% (I² = 99.6%). Authors did not identify publication bias based on the funnel plots analysis or Egger’s regression.

Methodology:
Authors included population-based studies/surveys conducted in India, published between 1990 and 2018. Studies were included if reported gender-wise prevalence of blindness/cataract blindness/CSC estimates for persons aged 50 years or above. This systematic review included studies calculating blindness prevalence from WHO definition, that is visual acuity of less than 3/60 in the better eye and with available correction, as well as the old definition (presenting visual acuity <6/60 in the better eye).

Authors conducted a search on Medline, Web of Science, Embase, Google Scholar and Turning Research Into Practice databases. Selection of studies for inclusion and data extraction was conducted by two reviewers independently, and risk of bias was assessed using the Critical Appraisal Skills Programme checklist.

Authors calculated pooled prevalence estimates using random effects on Stata for WHO definition of blindness obtained from rapid surveys. Heterogeneity was estimated using I² statistics.

Applicability/external validity:
Authors noted that findings of this study may be applicable to low and middle income countries. The present study showed lower CSC in women, which is consistent with previous studies and meta-analyses on CSC that demonstrated a gender difference in the utilisation of cataract surgical programmes in LMICs.

Geographic focus:
This review focused on included studies conducted in India, however, findings may be applicable to settings such as Nigeria where women have similar socio-economic characteristics.

Summary of quality assessment:
Low confidence was attributed to the conclusions about the effects of this review, as important limitations were identified. Authors did not use rigorous methods when searching for literature, indicating potential publication bias. The overall quality assessment of each study included in the review is not clear, as online supplementary tables were not accessible. In addition, biases were not avoided when screening studies for inclusion. Therefore, we cannot be confident in the findings of this review.