Regional disparities in effective cataract surgical coverage and relative quality gap in India: A systematic review and meta-analysis

Abstract

This study aimed to generate national-level pooled estimates of effective Cataract Surgical Coverage (eCSC)and Relative Quality Gap (RQG) and describe heterogeneity in these estimates across India. We registered the review protocol in PROSPERO (ID-CRD42024609587). We conducted and reported the systematic review and meta-analysis in accordance with the PRISMA 2020 reporting guidelines. Literature searches in PubMed, Scopus, Web of Science, and Embase identified studies in India published until November 4, 2024. Population-based cross-sectional and cohort studies reporting Cataract Surgical Coverage (CSC) and eCSC were included. Study characteristics and estimates were extracted, and quality was assessed using the JBI tool for prevalence studies. We estimated the pooled CSC, eCSC and RQG using random-effects meta-analysis (DerSimonian and Laird estimator) and performed the subgroup analyses and sensitivity analysis for heterogeneity assessment (I² statistic) using R. Seven studies were included in the systematic review, and four studies (34 survey reports) in the meta-analysis. Pooled estimates for CSC [57% (95% CI: 52% to 61%)], eCSC [36% (95% CI: 32% to 40%)], and RQG [37% (95% CI: 33%–40%)] showed high heterogeneity (I² >90%; P < 0.001). Subgroup analysis indicated regional differences for the coverage rates (P < 0.001), with the Northeast showing low coverage rates and low heterogeneity (CSC:36%, 95% CI (32%–42%), I2 = 0%; eCSC: 23%, 95% CI (16%–31%), I2 = 12.6%]. Low CSC, eCSC, and high RQG indicate that quality improvement must accompany efforts to increase coverage. High heterogeneity supports a decentralized, district-focused approach. A task force addressing barriers in the Northeast region could reduce regional inequities.

Cataracts are the leading cause of blindness globally, accounting for over 45% of all blindness cases.[1,2] In India, cataracts are responsible for nearly two-thirds of blindness cases.[3] Despite implementing the National Programme for Control of Blindness and significant advancements in cataract surgical techniques, cataracts continue to pose a major public health challenge in the country.[3,4]

Traditionally, cataract surgery accessibility and affordability have been assessed using the metric known as Cataract Surgical Coverage (CSC). It measures the proportion of individuals who receive surgery out of those who require it. In India, the CSC rates among individuals with pinhole visual acuity < 6/60 have improved from 65.7% in 2001–2002[5] to 89% in 2015–19.[6] The overall CSC at best corrected visual acuity (BCVA) <6/18 was reported to be 72.6%.[7]

However, this metric focuses primarily on the quantity of surgeries performed, with limited attention to the quality of surgical outcomes. Restoring visual acuity through successful cataract surgery improves quality of life, socioeconomic status, and overall wellbeing.[8] The proportion with best corrected visual acuity was reported to be >6/18 in 47% and 83.9% of the operated individuals in the 2001–02 and 2015–19 surveys, respectively.[5,6] In the 2015–19 surveys, 73.4% of total cataract-operated eyes had >6/12 best corrected visual acuity.[6] Other studies have reported varied proportions of favorable visual outcomes in cataract surgeries.[9,10,11]

To address the limitations of the traditional CSC metric, a new indicator, Effective Cataract Surgical Coverage (eCSC), was introduced in 2017.[12] It is the proportion of people with operable cataracts who receive surgery, which results in good visual outcomes. eCSC is a more comprehensive measure, reflecting access to cataract surgery and its quality.[12] By encompassing coverage and outcome quality, eCSC offers a more comprehensive measure for tracking progress toward universal eye health.[13] eCSC is listed in WHO indicators, in ‘WHO Report of the 2030 targets on effective coverage of eye care,’ and has been envisaged to achieve a 30% point increase in eCSC by 2030.[14] Thus, estimating the current eCSC would help us in gauging our journey toward the 2030 goals.

At the global level, analysis of datasets (2005–2013) from 20 countries estimated an average CSC of 53.7% and eCSC of 36.7%, with wide between-country variation in these parameters.[12] In a more recent secondary analysis of data from 148 RAAB (Rapid Assessment of Avoidable Blindness) surveys (2003–21) of 55 countries, the median CSC was 40%, and eCSC was 24·8%. This study also reported wide variation in CSC and eCSC by country.[15] Another indicator, the Relative Quality Gap (RQG), which considers the difference between CSC and eCSC, was also reported to vary from 10.8% to 73.4%.[15] The CSC, eCSC, and RQG estimates could help countries prioritize quality improvement or scaling up services. Countries with a low RQG must focus on improving access, and countries with a high RQG should prioritize quality improvement before increasing coverage.

Based on the data of 31 districts used in the 2015–19 national survey, a study reported CSC of 57.3%, eCSC of 36.7%, and an RQG of 36% in India.[16] This study has reported absolute and relative quality gaps for 31 districts, chosen randomly with regional representation, across India and explored gender, education, regional, urbanicity, and agewise differences too.[16] Other studies and surveys have also published their estimates for these indicators.[17,18] Synthesizing the findings from all potential sources, new and old, will give a more comprehensive picture, which is critical for informing national strategies aimed at reducing blindness and improving eye health outcomes. This study seeks to estimate the national-level pooled eCSC and quality gap, assess heterogeneity, and explore related factors such as geographic regions and gender in Indian settings. The results will help generate evidence-based recommendations for policymakers to understand the existing situation of the cataract surgery outcomes and their variations, which in turn will assist in optimizing interventions and enhancing the quality of eye care in India.

Methods

Study design

We conducted and reported the systematic review and meta-analysis in accordance with the “Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)” 2020 guidelines [Table S1]. The study protocol was preregistered in the “International Prospective Register of Systematic Reviews (PROSPERO)” under the registration number [ID-CRD42024609587]. Our review focused on addressing the research question: “What is the Effective Cataract Surgical Coverage (eCSC) and relative quality gap in India?” using the Population, Outcome, Study Design (POS) framework [Supplementary Table S2].

Table S1.

PRISMA Checklist (2020)

Section and Topic		Item #		Checklist item		Location where item is reported
Title
Title		1		Identify the report as a systematic review.		Pg 1
Abstract
Abstract		2		Made as per the Journal guidelines		Pg 1,2
Introduction
Rationale		3		Describe the rationale for the review in the context of existing knowledge.		Pg 3,4
Objectives		4		Provide an explicit statement of the objective(s) or question(s) the review addresses.		Pg 5
Methods
Eligibility criteria		5		Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses.		Supplementary Table S2
Information sources		6		Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted.		Pg 6
Search strategy		7		Present the full search strategies for all databases, registers and websites, including any filters and limits used.		Supplementary Table S4
Selection process		8		Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.		Pg 6, 7
Data collection process		9		Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.		Pg 7
Data items		10a		List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.		Pg 7
		10b		List and define all other variables for which data were sought (e.g. participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information.		Pg 7
Study risk of bias assessment		11		Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.		Pg 7
Effect measures		12		Specify for each outcome the effect measure(s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results.		Pg 7, Supplementary Table S3
Synthesis methods		13a		Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).		Pg 7
		13b		Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions.		Pg 7
		13c		Describe any methods used to tabulate or visually display results of individual studies and syntheses.		Pg 7
		13d		Describe any methods used to synthesize results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.		Pg 7
		13e		Describe any methods used to explore possible causes of heterogeneity among study results (e.g. subgroup analysis, meta-regression).		Pg 7
		13f		Describe any sensitivity analyses conducted to assess robustness of the synthesized results.		Pg 8
Reporting bias assessment		14		Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases).		NA
Certainty assessment		15		Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome.		Pg 8
Results
Study selection		16a		Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.		Pg 8, Figure 1
		16b		Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded.		Pg 8
Study characteristics		17		Cite each included study and present its characteristics.		Table 1
Risk of bias in studies		18		Present assessments of risk of bias for each included study.		Supplementary Table S5
Results of individual studies		19		For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g. confidence/credible interval), ideally using structured tables or plots.		Supplementary Table S6
Results of syntheses		20a		For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies.		Supplementary Table S5
		20b		Present results of all statistical syntheses conducted. If meta-analysis was done, present for each the summary estimate and its precision (e.g. confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect.		Figure 2, Supplementary Figures S1 (2.3MB, tif)
		20c		Present results of all investigations of possible causes of heterogeneity among study results.		Table 2 and Supplementary Fig S2 (1.8MB, tif)
		20d		Present results of all sensitivity analyses conducted to assess the robustness of the synthesized results.		Pg 13 and Supplementary Table S8
Reporting biases		21		Present assessments of risk of bias due to missing results (arising from reporting biases) for each synthesis assessed.		NA
Certainty of evidence		22		Present assessments of certainty (or confidence) in the body of evidence for each outcome assessed.		Pg 13, Supplementary Table S9
Discussion
Discussion		23a		Provide a general interpretation of the results in the context of other evidence.		Pg 12,13
		23b		Discuss any limitations of the evidence included in the review.		Pg 9
		23c		Discuss any limitations of the review processes used.		Pg 14, 15
		23d		Discuss implications of the results for practice, policy, and future research.		Pg 13-15
Other information
Registration and protocol		24a		Provide registration information for the review, including register name and registration number, or state that the review was not registered.		Pg 5
		24b		Indicate where the review protocol can be accessed, or state that a protocol was not prepared.		Pg 5
		24c		Describe and explain any amendments to information provided at registration or in the protocol.		NA
Support		25		Describe sources of financial or non-financial support for the review, and the role of the funders or sponsors in the review.		Pg 15
Competing interests		26		Declare any competing interests of review authors.		Pg 15
Availability of data, code and other materials		27		Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review.		NA

Table S2.

Inclusion and exclusion criteria for the systematic review and meta-analysis

POS Criteria		Inclusion Criteria		Exclusion Criteria
Population		Adults in India, all ages, all genders		—
Outcome		- Primary outcome: Effective Cataract Surgical Coverage (eCSC), defined as the proportion of operable and operated cataracts with a good quality outcome (visual acuity ≥6/12). - Secondary outcomes: Cataract Surgical Coverage (CSC), absolute and relative quality gap, other relevant outcomes as reported by studies.		—
Outcome Measure		Proportion		—
Study Design		Community-based cross-sectional surveys, intervention studies, cohort studies		Case studies, qualitative studies, opinion pieces, case-control studies, reviews
Other		- Databases: MEDLINE (PubMed), EMBASE, Scopus, Web of Science - Citation searching and grey literature review including RAAB surveys and government reports - Geography: India - Species: Humans - Type of studies: Published studies - Date of search: Up to 04 November 2024		—

The primary outcome was eCSC, which is the proportion of individuals in a population who have had cataract surgery and have a good postoperative visual acuity (6/12 or better) compared to those who have operable or operated cataracts (VA <6/12). Other outcomes were CSC and relative quality gap. CSC is the proportion of people in a population who have operated cataracts out of those with operable or operated cataracts (VA <6/12). RQG is the difference between CSC and eCSC, expressed as a proportion of CSC with lower values reflecting better quality of cataract surgical services [Supplementary Table S3].

Table S3.

Formulae to calculate Cataract Surgery Coverage (CSC0 effective Cataract Surgical Coverage (eCSC) and Relative Quality Gap (RQG)

Indicators		Formula
CSC		x+y/(x+y+z) *100		x=individuals with unilateral pseudo/aphakia (i.e. operated cataract) and operable cataract in the other eye; y=individuals with bilateral pseudo/aphakia, regardless of visual acuity; z=individuals with bilateral operable cataract.
eCSC		a+b/(x+y+z) *100		a=individuals with unilateral pseudo/aphakia achieving presenting visual acuity of 6/12 or better in the operated eye and operable cataract in the other eye; b=individuals with bilateral pseudo/aphakia achieving presenting visual acuity of 6/12 or better; in at least one eye x=individuals with unilateral pseudo/aphakia (i.e. operated cataract) and operable cataract in the other eye; y=individuals with bilateral pseudo/aphakia, regardless of visual acuity; z=individuals with bilateral operable cataract.
RQG		(CSC-eCSC)/CSC*100

Eligibility criteria [Supplementary Table S2]

Inclusion Criteria: Studies were included if (1) they were conducted in India in individuals aged >18 years, (2) they reported an eCSC, and (3) the study design used was population-based cross-sectional surveys and cohort and intervention studies.

Exclusion Criteria: We excluded studies that did not report on eCSC and were hospital-based studies, case series, review articles, qualitative studies, and opinions.

Data sources and search strategy

We comprehensively searched four electronic databases: PubMed, Embase, Scopus, and Web of Science [Supplementary Table S4]. We first developed the PubMed search strategy using keywords and “Medical Subject Headings (MeSH)” terms. It was then adapted for the other databases [Supplementary Table S4]. Additionally, reference lists of eligible articles and gray literature, including RAAB survey reports and government publications, were screened to identify further studies. We used Nested Knowledge software to manage citations, remove duplicates, and streamline the screening process. Two authors (GP and MK) independently performed the screening, data extraction, and quality assessment tasks. Disagreements between them were resolved through consensus meetings. The third reviewer (APG) was consulted for adjudication if consensus was not reached.

Table S4.

The adjusted search terms as per searched electronic databases (Date of Search 04/11/2024)

Search No.		Query		Results
PubMed
#1		(cataract surg*[Title/Abstract]) AND (effective[Title/Abstract])		2,476
#2		((cataract surg*[Title/Abstract]) AND (effective[Title/Abstract])) OR (eCSC[Title/Abstract])		2,615
#3		((India[Affiliation]) OR (India[MeSH Terms])) OR (India[Title/Abstract])		842,518
#4		(((cataract surg*[Title/Abstract]) AND (effective[Title/Abstract])) OR (eCSC[Title/Abstract])) AND (((India[Affiliation]) OR (India[MeSH Terms])) OR (India[Title/Abstract]))		219
Embase
#1		‘cataract surg*’:ab,kw,ti AND ‘effective’:ab,kw,ti		3206
#2		ecsc:ab,kw,ti		254
#3		#1 OR #2		3445
#4		‘india’/de OR india:ab,kw,ti,ca		1063392
#5		#3 AND #4		218
#6		#3 AND #4 AND [humans]/lim AND [english]/lim		214
Scopus
#1		((TITLE-ABS-KEY(“cataract surg*”) AND TITLE-ABS-KEY(effective))) OR (TITLE-ABS-KEY(eCSC))		3801
#2		(TITLE-ABS-KEY(india) OR AFFILCOUNTRY(India))		3,785,511
#3		(((TITLE-ABS-KEY(“cataract surg*”) AND TITLE-ABS-KEY(effective))) OR (TITLE-ABS-KEY(eCSC))) AND ((TITLE-ABS-KEY(india) OR AFFILCOUNTRY(India)))		300
#4		(((TITLE-ABS-KEY(“cataract surg*”) AND TITLE-ABS-KEY(effective))) OR (TITLE-ABS-KEY(eCSC))) AND ((TITLE-ABS-KEY(india) OR AFFILCOUNTRY(India))) AND (LIMIT-TO (EXACTKEYWORD,”Human”)) AND (LIMIT-TO (LANGUAGE,”English”))		231
Web of Science
#1		(TS=(“cataract surg*”)) AND TS=(effective)		2464
#2		TS=(eCSC)		258
#3		#1 OR #2		2708
#4		(TS=(India)) OR AD=(India)		2033314
#5		#3 AND #4		224
#6		#3 AND #4 and English (Languages)		224

Screening process

After removing duplicates, two authors (GSP and MK) independently conducted a two-stage screening process using the Nested Knowledge software. In the first stage, we screened titles and abstracts using the eligibility criteria. Eligible articles were advanced to the second stage, in which full texts of potentially relevant studies were assessed to confirm eligibility. Articles meeting the eligibility criteria were taken up for data extraction.

Data extraction

Two authors (GSP and MK) independently performed data extraction using a data extraction sheet in Microsoft Excel for the following variables:

• Study characteristics: Author, year of survey, year of publication, region, study design, population enrolled and examined.

• Population characteristics: Age distribution, sex distribution.

• Outcomes: Estimates of CSC, eCSC, and RQG.

Quality assessment

Two reviewers (GSP and MK) independently assessed the quality of the included studies by using the JBI Critical Appraisal Checklist for prevalence studies. The assessment criteria included the study’s sampling frame, sampling technique, sample size, response rate, description of study participants, outcome measurement, and data analysis methods.

Data synthesis and analysis

Since all surveys included in the meta-analysis used cluster sampling, we adjusted for intra-cluster correlation by applying study-specific design effects (DEFF).[16] Design effects for cataract surgical coverage (CSC) and effective CSC (eCSC) were available for 32 of the 35 surveys. For the three surveys that did not report DEFF, we imputed the median DEFF calculated from the other 32 surveys. Each study’s original sample size was divided by its DEFF to obtain an effective sample size, and event counts were rescaled accordingly; these cluster-adjusted figures were then used to derive study-level precision for the pooled analysis.

The pooled estimates of eCSC, CSC, and RQG were calculated using a random-effects model to account for between-study heterogeneity, and results were displayed as forest plots. The degree of heterogeneity was quantified using the Chi-squared test and I² statistic.[19] The I² of 25%, 50%, and 75% were considered cut-offs for low, moderate, and high heterogeneity. We performed subgroup and sensitivity analyses to explore sources of heterogeneity. All statistical analyses were performed using the “metafor” package in R [v4.2.2].[20] We estimated the weighted average of CSC, eCSC, and RQG for 2015, 2016, 2017, 2018, and 2021 and have depicted the year-wise trend using a line diagram. We assessed the certainty of the pooled outcome estimates in the meta-analysis using a modified GRADE framework.[21,22]

Results

Database search yielded 841 articles, of which 480 were identified as duplicates and removed before screening. The title and abstract screening of the 361 papers was conducted, resulting in the exclusion of 356 articles deemed unsuitable. In addition to six articles fulfilling the eligibility criteria,[15,16,17,18,23,24] we identified three additional studies through a citation search.[25,26,27] After full test screening of these nine identified studies, two were excluded – one of the two studies reporting from the same dataset[15] and another study that did not report eCSC.[24] Thus, a total of seven studies were found to be eligible and included in the data extraction. The quality assessment of the included studies is illustrated in the supplement file [Supplementary Table S5]. All seven studies were included in the systematic review.[16,17,18,23,25,26,27] Four articles either reported the denominators for calculating the eCSC, or we could extract the numbers from the given data. These four articles, which included 34 survey reports, were included in the meta-analysis.[16,17,18,25] The PRISMA flow chart depicts the article review and selection process [Fig. 1].

Table S5.

Quality assessment of included studies with the use of JBI

First author, Year of publication		Q1		Q2		Q3		Q4		Q5		Q6		Q7		Q8		Q9		Overall appraisal		Remarks
Gupta V, 2024[16]		Yes		Yes		Yes		Yes		Yes		Yes		Yes		Yes		Yes		Include		Mentioned that survey conducted as per the RAAB protocol
Gupta S, 2024[17]		Yes		Yes		Yes		Yes		Yes		Yes		Yes		Yes		Yes		Include		A community based longitudinal cohort study
Vashist P, 2024[18]		Yes		Yes		Yes		Yes		Yes		No		Yes		Yes		Yes		Include		Mentioned that survey conducted as per the RAAVI protocol
Marmamula S, 2024[23]		Yes		Yes		Not clear		Yes		Yes		Yes		Yes		No		Yes		Include		Mentioned that survey conducted as per the RAAB protocol
ICEH, 2024[25]		Yes		Yes		Yes		Yes		Yes		Not clear		Not clear		Yes		yes		Include		Mentioned that survey conducted as per the RAAB protocol
Bhardwaj A, 2023[26]		Yes		Yes		Yes		Yes		Yes		No		Yes		Yes		Yes		Include		Mentioned that survey conducted as per the RAVI protocol
Jolly E,2022[27]		Yes		Yes		Not clear		Yes		Yes		Yes		Yes		No		Yes		Include		Mentioned that survey conducted as per the RAAB protocol

Questions- JBI checklist. Q1. Was the sample frame appropriate to address the target population. Q2. Were study participants sampled in an appropriate way? Q3. Was the sample size adequate? Q4. Were the study subjects and the setting described in detail? Q5. Was the data analysis conducted with sufficient coverage of the identified sample? Q6. Were valid methods used for the identification of the condition? Q7. Was the condition measured in a standard, reliable way for all participants? Q8. Was there appropriate statistical analysis? Q9. Was the response rate adequate, and if not, was the low response rate managed appropriately?

Figure 1.

PRISMA flow chart showing studies included in the systematic review and meta-analysis of Cataract Surgical Coverage (CSC), effective Cataract Surgical Coverage (eCSC), and Relative Quality Gap (RQG)

The seven studies considered for the systematic review were conducted from 2015 to 2021. Table 1 and Supplementary Table S6 describe their baseline characteristics. The studies were conducted across the six geographic regions of India.[16,17,18,23,25,26,27] The majority of the studies have district level data. However, two studies have reported for multiple districts together[23,26] and a study reported for the urban part of one district.[25] Three studies focused on individuals aged 40 and above,[23,25,26] while four studies targeted those aged 50 and above.[16,17,18,27] Response rates ranged from 80% to 90% in four studies[17,18,25] and exceeded 90% in three studies.[16,23,27] Six studies used a cross-sectional study design,[16,18,19,25,26,27] four of which employed the RAAB survey protocol,[16,19,25,27] and two used the RAAVI method.[18,26] One was a population-based longitudinal study incorporating a comprehensive survey at baseline and 12-month follow-up.[17] Four studies described their methodology in detail.[16,18,23,26] For one study, we referred to another article that described the methodology in detail.[17] Two studies did not explicitly define the methods but mentioned they followed the RAAB protocol.[25,27]

Table 1.

Characteristics of the studies included in the index analysis

Author, Year of publication		Year of survey		Region		Districts (State)		Study design		Age of participants		Gender Male (%)		Gender Female (%)		Number of individuals examined in the survey (n)
Gupta V, 2024[16]		2015- 2019		North, South, West, East, Northeast, Central		West Delhi, Yamuna Nagar, Kapurthala, Sirohi, Sikar, Bilaspur, Jammu, Banda, Ambedkar Nagar, Bijnor, Kjanjgir-Champa, Khargone, Guna, North Goa, Khera, Thane, Wardha, Howrah, Birbhum, Sitamarhi, Vaishali, Purbhi Singhbum, Nayagarh, Kadapa, Thrissur, Virudhnagar, Chikmangalur, Warangal, Nalbari, Thoubai, East Siang		RAAB cross-sectional		≥50 yrs		42.7		57.3		85135
Gupta S, 2024[17]		2018		South		Theni (Tamil Nadu)		12-month follow-up survey of a longitudinal study		≥50 yrs		42.1		57.9		7075
Vashist P, 2024[18]		2021		North		Gurugram (Haryana)		RAAVI cross-sectional		≥50 years		38.4		61.6		783
Marmamula S, 2024[23]		2014-2017		South		Adilabad, Mahbubmagar, Warangal, and Khammam (Telangana)		RAAB cross-sectional		≥40 years		45.4		54.6		11238
ICEH#, 2024[25]		2017		West		Pune- Urban (Maharashtra)		RAAB cross-sectional		≥40 years		44.7		55.3		3221
Bhardwaj A, 2023[26]		NA		East		Ganjam and Khorda, (Odisha)		RAAVI cross-sectional		≥40 years		44.8		55.2		3745
Jolly E,2022[27]		2021		East		Alipurduar (West Bengal)		RAAB cross-sectional		≥50 years		42.7		57.3		3380

#ICEH: International Centre for Eye Health *RAAB: Rapid Assessment of Avoidable Blindness

Table S6.

Region, Districts, States and year of survey and individual study estimates of the 34 studies included in the meta-analysis

Author, Year of publication		Year of survey		Districts		State		Region		Denominator for estimation of CSC and eCSC (n)		CSC (%)		eCSC (%)		RQG (%)
Gupta V, 2024[16]		2015		West Delhi		Delhi		North		587		77.17		53.66		30.24
Gupta V, 2024[16]		2015		Yamuna Nagar		Haryana		North		515		77.09		52.23		31.99
Gupta V, 2024[16]		2016		Kapurthala		Punjab		North		757		73.32		46.76		36.22
Gupta V, 2024[16]		2017		Sirohi		Rajasthan		North		757		61.29		42.14		31.25
Gupta V, 2024[16]		2015		Sikar		Rajasthan		North		682		63.78		39.59		37.93
Gupta V, 2024[16]		2016		Bilaspur		Himachal Pradesh		North		599		65.11		39.23		39.74
Gupta V, 2024[16]		2016		Jammu		Jammu and Kashmir		North		595		59.83		26.05		56.46
Gupta V, 2024[16]		2016		Banda		Uttar Pradesh		Central		776		64.05		43.56		32.19
Gupta V, 2024[16]		2017		Khargone		Madhya Pradesh		Central		559		55.28		33.27		40.13
Gupta V, 2024[16]		2015		Bijnor		Uttar Pradesh		Central		611		61.21		30.44		50.40
Gupta V, 2024[16]		2016		Ambedkar Nagar		Uttar Pradesh		Central		596		48.66		29.87		38.62
Gupta V, 2024[16]		2018		Kjanjgir-Champa		Chattisgarh		Central		853		43.73		26.96		38.34
Gupta V, 2024[16]		2017		Guna		Madhya Pradesh		Central		867		42.56		22.95		46.34
Gupta V, 2024[16]		2018		North Goa		Goa		West		637		64.68		51.02		21.12
Gupta V, 2024[16]		2016		Khera		Gujarat		West		630		74.44		43.65		41.15
Gupta V, 2024[16]		2016		Thane		Maharashtra		West		740		59.59		38.65		35.07
Gupta V, 2024[16]		2016		Wardha		Maharashtra		West		612		55.39		31.21		43.66
Gupta V, 2024[16]		2017		Howrah		West Bengal		East		660		59.55		41.06		31.04
Gupta V, 2024[16]		2018		Sitamarhi		Bihar		East		673		42.64		30.01		29.62
Gupta V, 2024[16]		2017		Vaishali		Bihar		East		578		42.39		27.85		33.88
Gupta V, 2024[16]		2017		Birbhum		West Bengal		East		539		44.53		26.90		39.58
Gupta V, 2024[16]		2018		Purbhi Singhbum		Jharkhand		East		768		38.28		26.17		31.63
Gupta V, 2024[16]		2016		Nayagarh		Odisha		East		622		29.42		9.65		67.21
Gupta V, 2024[16]		2017		Kadapa		Andhra Pradesh		South		1074		69.09		49.35		28.71
Gupta V, 2024[16]		2018		Thrissur		Kerala		South		1099		59.96		40.40		32.63
Gupta V, 2024[16]		2016		Virudhnagar		Tamil Nadu		South		1215		64.28		39.84		38.03
Gupta V, 2024[16]		2017		Chikmangalur		Karnataka		South		758		51.98		35.22		32.23
Gupta V, 2024[16]		2017		Warangal		Telangana		South		1027		51.31		32.13		37.38
Gupta V, 2024[16]		2016		Nalbari		Assam		NE		679		38.14		26.36		30.89
Gupta V, 2024[16]		2017		Thoubai		Manipur		NE		325		34.46		22.15		35.71
Gupta V, 2024[16]		2018		East Siang		Arunachal Pradesh		NE		609		36.12		20.85		42.27
Gupta S, 2024[17]		2018		Theni		Tamil Nadu		South		1402		75.68		54.49		27.99
Vashist P, 2024[18]		2021		Gurugram		Haryana		North		178		75.84		61.80		18.52
Marmamula S, 2024[23]		2014-2017		Adilabad, Mahbubmagar, Warangal, Khammam		Telangana		South		NA		54.2		39.9		26.4
ICEH, 2024[25]		2017		Pune		Maharashtra		West		1115		58.30		32.29		44.62
Bhardwaj A, 2023[26]		NA		Ganjam and Khorda		Odisha		East		NA		47.4		35.02		26.1
Jolly E,2022[27]		2021		Alipurduar		West Bengal		East		NA		83.9		56.5		32.66

Across all studies, the threshold for operable cataract of visual acuity threshold of <6/12 has been reported and considered in this review.[16,17,18,23,25,26,27] Some studies have reported estimates for other cataract surgical thresholds too (6/18, 6/60, 3/60).[16,25,26] For cataract diagnosis, two studies used torchlight lens assessments for undilated pupils,[18,26] and one study used slit-lamp examination after dilation.[17] One study employed a combination of torchlight, direct ophthalmoscopy, and handheld slit-lamp examination,[16] while two studies relied solely on direct ophthalmoscopy in dim illumination.[23,27] The RAAB survey report from Pune did not specify the assessment method explicitly in their report.[25]

Six studies used sample size calculations to estimate the prevalence of blindness and visual impairment.[16,17,23,25,26,27] One study calculated a sample size of 217 individuals for the denominator in the eCSC equation based on an assumed 40% effective cataract surgical coverage.[16] All studies employed a multistage cluster sampling methodology.[16,17,18,23,25,26,27] To ensure reliability, four studies implemented training and assessed inter-observer agreement,[17,18,24,26] one study conducted training alone,[27] and two studies mentioned adherence to the RAAB standard protocol for survey examinations that include standardized training and assessing inter-observer agreement.[16,25]

Four studies in which the numerator and denominators for eCSC, CSC, and RQGs either were reported or could be estimated from given data were included in the meta-analysis.[16,17,18,25] In one study, we obtained the denominator for eCSC and CSC from the dataset available in the public domain.[25] For another study, we obtained this number based on the percentage of enrolled individuals included in the eCSC estimation, which was reported for 31 districts.[16] In two studies, the denominators were explicitly mentioned.[17,18]

Of the four studies, one study reported district-wise data for 31 districts.[16] Hence, each district has been taken as a separate report for meta-analysis. Therefore, 34 reports were included in the meta-analysis to determine the pooled estimates of CSC, eCSC, and RQG along with the heterogeneity.

The RAAB surveys are ideally carried out at a district or province level with a sample size between 2000 and 5000 people aged over 50 years. As the surveys use a two-stage cluster sampling method, the findings can be generalized to the entire district. Among the people examined in the survey, those with operable cataract visual impairment are eligible for the calculation of CSC and eCSC.

Cataract surgical coverage (CSC)

The denominator and numerator values for CSC and eCSC were extracted from four studies, together encompassing 34 district-level survey reports across India. One study reported data from 31 districts across six regions.[16] The denominators per district ranged from 325 to 1215 individuals with operable/operated cataracts, with a median of 660 and an IQR of 596 to 776. The other three studies contributed single-district data: Theni, Tamil Nadu (n = 1402);[17] Gurugram, Haryana (n = 178);[18] and urban Pune, Maharashtra (n = 1115).[25] Since all surveys were based on two-stage cluster sampling, we adjusted for study-specific design effects. After adjustment, the pooled denominator reduced from 24,694 to 16,084, and the operated cataracts from 14,105 to 9286. The sample size for each survey is mentioned in Supplementary Table S6 (raw) and the forest plots (adjusted for design effect).

The CSC reported by individual studies ranged from 30% to 77%. The overall pooled CSC was 57% (95% CI: 52%–61%) with a prediction interval of 26% to 82% and high heterogeneity (I² = 96.8%, P < 0.001) [Fig. 2]. The subgroup analysis revealed significant differences in CSC between regions (P < 0.001). CSC was the highest in the North (69%) and lowest in the Northeast (36%) region. Most regions, except the Northeast, showed high heterogeneity (I² >80%) [Table 2, Supplementary Fig. S1 ^{(2.3MB, tif)} ]. Three studies reported CSC for males and females.[17,18,25] Gupta et al.[16] depicted the gender-wise eCSC with 95% CIs for each district along with the relative gender gap. The overlap of the 95% CIs for males and females indicates there was no gender disparity in CSC coverage. High heterogeneity was present in the CSC of males (I² = 94%) and females (I² = 92%), across the included studies [Supplementary Table S7].

Figure 2.

Forest plots of pooled Cataract Surgical Coverage (CSC) and Effective Cataract Surgical Coverage (eCSC) in India

Table 2.

Subgroup analysis of CSC, eCSC, and relative quality gap based on geographic regions

Regions		Number of studies		Estimates expressed as percentage with 95% CI		I2 (%)		P value for between-group differences
Cataract Surgical Coverage (CSC)
North		8		69 [63; 75]		89.2		<0.001
Central		6		53 [43; 62]		95.4
West		5		63 [53; 72]		90.0
East		6		43 [32; 53]		93.0
South		6		62 [52, 72]		96.7
Northeast		3		36 [32; 41]		0
Effective Cataract Surgical Coverage (eCSC)
North		8		45 [36; 54]		93.6		< 0.001
Central		6		31 [24; 39]		93.5
West		5		39 [29; 50]		89.6
East		6		26 [16; 38]		96.4
South		6		42 [33; 51]		95.9
Northeast		3		23 [16; 30]		12.6
Relative Quality Gap (RQG)
North		8		35 [27; 44]		87.9		0.241
Central		6		41 [34; 48]		84.0
West		5		37 [25; 50]		91.4
East		6		38 [24; 54]		89.8
South		6		33 [28; 37]		77.1
Northeast		3		36 [23; 51]		2.90

Table S7.

Pooled analysis of CSC, eCSC, and relative quality gap based on gender

Gender		Number of studies		Pooled estimate expressed as percentages with 95% CI		I2 (%)		P
Cataract Surgical Coverage
Male		3		69 (38-93)		94.1		<0.001
Female		3		70 (45-90)		91.7		<0.001
Effective Cataract Surgical Coverage
Male		3		48 (18-79)		96.4
Female		3		49 (10-89)		98.0		<0.001
Relative Quality Gap
Male		3		27 (9-49)		78		0.011
Female		3		26 (0.01-74)		95.4		<0.001

Effective cataract surgical coverage (eCSC)

There were 6129 individuals who had cataract surgery with good postoperative visual acuity among 16,671 individuals with operable or operated cataracts. The eCSC across individual studies ranged widely, from 10% to 62%, with a pooled eCSC of 36% (95% CI: 32% to 40%). The prediction interval for eCSC was 15% to 60% with high heterogeneity (I² = 96%, P < 0.001) [Fig. 2]. There were significant differences in eCSC between the regions, with North (45%) and South (42%) regions reporting relatively higher eCSC and the Northeast (NE) region having the lowest eCSC (23%) (P < 0.001) [Table 2, Supplementary Fig. S1 ^{(2.3MB, tif)} ]. However, it is pertinent to mention that despite the slight variation in point estimates, the 95% confidence intervals of the eCSC of Gupta et al.[16] and the index meta-analysis overlap, indicating similar eCSC rates between them. Most regions exhibited high heterogeneity (I² >90%), except for the Northeast, which showed low heterogeneity (I² = 12.6%) [Table 2]. Three studies reported eCSC for males and females at the district level.[17,18,25] The 95% CIs for males and females overlapped, indicating no significant gender disparity in eCSC. Both subgroups exhibited high heterogeneity (I² >97%). [Supplementary Table S7]

Relative quality gap (RQG)

The RQG estimates across studies ranged from 19% to 67%. The overall pooled RQG was 37% (95% CI: 33%–40%) with a prediction interval of 21% to 54% and high heterogeneity (I² =86.1%) [Supplementary Fig. S2 ^{(1.8MB, tif)} ]. Though the RQG ranged from 33% in the South region to 41% in the Central region, there were no statistically significant differences in RQG across the six regions (P = 0.241) [Table 2]. Most regions exhibited high heterogeneity (I² >75%), except for the Northeast, which showed low heterogeneity (I² = 2.9%) [Table 2, Supplementary Fig. S2 ^{(1.8MB, tif)} ]. There was no evidence of significant gender disparity in the RQG with an overlap of their 95% CIs. Heterogeneity was high for both subgroups (I² = 84% for males, I² =97% for females) [Supplementary Table S7].

The study based in Telangana reported an overall CSC of 54.2%, eCSC of 39.9%, and RQG of 14.4%. We could not include the estimates for the four districts included in this study in the meta-analysis as the numerators and denominators for calculating the indicators were not reported.[23]

Sensitivity analysis

Individuals included in all the studies were aged ≥50 years, except for the study in Pune, in which the inclusion criterion was age ≥40 years.[25] We performed a sensitivity analysis by excluding the study done in Pune [Supplementary Table S8]. The pooled CSC was 57% (95% CI: 52%–62%) with I² = 97%, P < 0.001. The pooled eCSC was 36 (95% CI: 32%–40%) with I² = 96%, P < 0.001. The RQG was estimated to be 36% (95% CI: 33%–40%), I² = 86%, P < 0.001. Supplementary Table S8 also depicts the results of the sensitivity analysis conducted by omitting two studies, which did not use the RAAB study design.[26,27] The pooled prevalence of CSC, eCSC, and RQG did not change considerably with this step.

Table S8.

Sensitivity analysis omitting a study due to age of participants and two studies due to different study designs

Outcome		One study (Age Criterion ≥40 yrs) was omitted. All studies with an age criterion of ≥50 yrs were retained						Two studies (One RAAVI study and one Longitudinal study) were omitted; All RAAB studies were retained
		Pooled estimates (%) (95% CI)		I2 (%)		P		Pooled estimates (%) (95% CI)		I2 (%)		P
CSC		57 (52-62)		96.9		<0.001		55 (51-60)		96.5		<0.001
eCSC		36 (32-40)		96.3		<0.001		34 (31-38)		95.6		<0.001
RQG		36 (33-40)		85.7		<0.001		37 (34-40)		84.8		<0.001

Upon assessing the certainty of pooled estimates of CSC, eCSC, and RQG based on the modified Grade framework criteria, we concluded that there was low certainty for all three parameters, mainly due to issues in indirectness and inconsistency [Supplementary Table S9].

Table S9.

Certainty assessment in the pooled estimates of the outcomes in the meta-analysis

Outcomes		Risk of bias		Imprecision		Indirectness		Inconsistency		Sample size		Certainty
CSC		Not serious*		Not serious#		Serious$		Serious†		16084		Low‡
eCSC		Not serious*		Not serious#		Serious$		Serious†		16671		Low‡
RQG		Not serious*		Not serious#		Serious$		Serious†		9284		Low‡

*Majority of the JBI quality assessment domains for the included studies were satisfied. ^#95% CI of the pooled estimates were narrow and the sample size on which the pooled estimates were based were large. ^$Varied methods and age group were included in the studies of the pooled estimate. ^†High heterogeneity between the studies. ^‡Initial Certainty in the pooled estimate was taken as ‘High’ and rated down to ‘Low’ certainty owing to serious issues in Indirectness and Inconsistency domains of the outcomes

Fig. S3 ^{(494.9KB, tif)} [Supplementary File S3 ^{(494.9KB, tif)} ] depicts the weighted annual means for cataract-surgical coverage, effective CSC (eCSC), and the relative quality gap. Between 2015 and 2018, both the reach and effectiveness of cataract services declined. CSC declined from 69.3% to 54.7%, and eCSC dropped from 43.4% to 38.0%. The relative quality gap showed a modest reduction from 37.9% to 31.7%. In 2021, however, CSC showed a sharp rise to 75.8%, and eCSC rose even more steeply to 61.8%, resulting in a halving of the RQG to 18.5%.

Discussion

This systematic review provides critical insights into the status of cataract surgical services in India, highlighting significant gaps in coverage and quality despite various national initiatives. The pooled CSC of 57% indicates that 43% of individuals with operable cataracts remain untreated. Regional disparities are stark, with the lowest CSC observed in the Northeast (37%). These findings are consistent with earlier studies attributing low CSC to various attitudinal, economic, and personal barriers.[28,29,30] Although the National Program for Prevention of Blindness and Visual Impairment (NPCBVI) has undertaken initiatives such as constructing eye wards and deploying mobile ophthalmic units in underserved regions,[31] further collaboration with transportation and infrastructure sectors is crucial to address these external barriers effectively.

The pooled Effective Cataract Surgical Coverage of 36% indicates that only 36% of individuals with operable and operated cataracts achieve a presenting visual acuity of ≥ 6/12. The RQG of 37% reveals that over one-third of individuals who underwent cataract surgery did not achieve a presenting visual acuity of ≥6/12. These findings underscore the urgent need to improve the quality of cataract surgical services. Poor postsurgical visual outcomes often result from uncorrected refractive errors, uncorrected aphakia, surgical complications, or posterior segment disorders.[32,33,34,35] Addressing these issues requires strengthening and monitoring systems to ensure adherence to quality standards and regular capacity-building initiatives for healthcare personnel.[36] In the recently introduced subnational certification of cataract blindness backlog-free status campaign, quantitative measures like CSC have been combined with qualitative outcomes such as the proportion of individuals achieving an visual acuity of >6/12.[37] This is a pragmatic approach to prioritizing the quality of services.

Globally, the median eCSC in populations aged ≥50 years is 17.2%, with a median RQG of 33.9%. For the South-East Asia Region, the median eCSC is 40.4%, with a RQG of 27.6%.[14] The wide variation in these estimates across WHO regions is likely influenced by demographic, geographical, and service quality factors.

In this review, too, high heterogeneity was observed among studies for CSC, eCSC, and RQG, presenting challenges in interpreting the pooled meta-analysis results. In our sensitivity analyses, the results remain consistent after excluding studies with different age criteria and study designs, which suggests that the findings are robust and not overly influenced by these studies. Although the RAAB protocol enables standard assessment of blindness, systemic and population-level factors, such as demographic differences, socioeconomic status, healthcare funding, availability of skilled personnel, diagnostic tools, and infrastructure disparities, are likely contributors to this heterogeneity. This district-level heterogeneity supports the current strategy of planning, implementing, and monitoring the interventions under the national program through the district-level societies. The subnational certification of cataract blindness backlog-free status campaign also considers the block and district-level status for certification purposes.[37] The recently announced Mission Mode Cataract Surgery campaign (Netra Jyoti Abhiyan), launched to address the cataract backlog, also emphasizes district-level planning.[38] This decentralized approach has the potential to mitigate intraregional variations effectively. The subgroup analysis revealed high heterogeneity in estimates across regions, except for the northeastern region, where the low heterogeneity suggests common underlying factors for low CSC, eCSC, and high RQG. Challenges in this region include inadequate infrastructure, manpower shortages, limited literacy, challenging geography, cultural beliefs, low health spending, and overall economic constraints.[39] A study among the elderly in this region highlighted bad roads, poor health, costs, and scepticism about surgical outcomes as major barriers to eye care.[40] Reliance on traditional eye care practices further complicates service delivery.[41] Addressing these challenges necessitates the establishment of a regional task force to identify and implement strategies tailored to the Northeast.

Interestingly, previous reports suggest better CSC and eCSC estimates among men than women.[15,42,43] However, this review found no significant gender disparities based on the overlap of 95% confidence intervals. This finding may be limited by the small number of studies reporting gender-specific coverage rates, resulting in wide confidence intervals.

One of the strengths of the current systematic review is the inclusion of four major databases for identifying the studies. The meta-analysis is based on four good-quality studies with 34 reports. The current review can serve as a baseline report for assessing India’s progress toward achieving the 2030 targets of increasing eCSC by 30 percentage points. Though the high heterogeneity between the studies limits the utility of the pooled estimates of the outcomes, it underlines the importance of a decentralized targeted approach in planning and monitoring program interventions. While the sample size used to get the pooled estimates appears to be small for a country the size of India, they nonetheless represent populations from 34 districts covering diverse geographic regions.

For the time -trends, few survey reports were available for each calendar year, with only one report for 2021. This limits the precision of annual point estimates. Consequently, apparent year-to-year fluctuations—particularly the 2021 peak—should be interpreted with caution. Additional RAAB surveys, particularly after 2020, are required to confirm the observed upward trend.

There is limited evidence base—seven studies in the systematic review, of which four studies with 34 survey reports were meta-analyzed—to describe the national landscape of cataract service coverage and quality in India. We recommend that a coordinated program of periodic, standardized RAAB-plus surveys across all states should be mandated, with compulsory reporting of CSC and eCSC, to build a more robust and nationally representative evidence base. Such systematic data generation will be essential for monitoring India’s progress toward the WHO 2030 targets for effective cataract surgical coverage.

Conclusion

Given the eCSC and RQG estimates, government efforts should prioritize enhancing the quality of cataract surgical services alongside expanding coverage. Regional disparities must be considered when planning eye care services. The observed high heterogeneity supports the appropriateness of a decentralized approach. Additionally, formulating a regional task force for the northeastern region, considering its lower coverage and significant quality gaps, is critical. Such strategies are pivotal to achieving the goals of national initiatives and reducing cataract-related visual impairment in India.

Authors’ contribution details

GSP and AGP conceptualized the study and designed the protocol. GSP did the PROSPERO registration. GP, MFK, and AGP did the literature search. GP, MFK AGP, PCG and VKI did screening, collected data, and assessed the quality of the studies. GSP, CG and AGP analysed the data. GSP, MFK and AGP interpreted the results. GSP and AGP wrote the initial draft of the manuscript. GSP, MFK, AGP, PCG, VKI and CG have contributed to manuscript preparation and manuscript editing. Finally, GSP and AGP edited the final draft with the team’s amendments of critical revisions and essential suggestions. All authors had full access to all the data in the study and had the final responsibility for the decision to submit for publication.

Conflicts of interest:

There are no conflicts of interest.

Figure S1

Region-wise sub-group analysis of Cataract Surgical Coverage (CSC) and effective Cataract Surgical Coverage (eCSC)

Figure S2

Forest plot of pooled Relative Quality Gap (RQG) and region-wise sub-group analysis of Relative Quality Gap (RQG) in India

Figure S3

Year-wise trends of Cataract Surgical Coverage (CSC), effective Cataract Surgical Coverage (eCSC) and Relative Quality Gap (RQG)

Funding Statement

Nil.