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Epidemiology and global burden

TL;DR — Cataract is the leading single cause of blindness worldwide and the second leading cause of moderate-or-severe vision impairment after uncorrected refractive error (Flaxman 2017, PMID 29032195). Two current global estimates coexist and are not interchangeable: the GBD cause analysis restricted to adults ≥50 gives 15.2 million blind (95% UI 12.7–18.0) and 78.8 million with MSVI (67.2–91.4) in 2020 (PMID 33275949), while an all-ages cataract-specific meta-analysis gives 17.0 million blind (39.6% of all blindness) and 83.5 million with MSVI (28.3%) (PMID 38461217). Between 1990 and 2020 age-standardised cataract blindness prevalence fell 27.5% while the absolute cataract-blind count rose 29.7% and the MSVI count rose 93.1% — the defining epidemiological fact of the field (PMID 38461217). Incidence in an ageing population is high: 10-year person-specific incidence in the Blue Mountains Eye Study was 36.0% for nuclear, 28.0% for cortical and 9.1% for PSC cataract, with 17.8% undergoing surgery (Kanthan 2008, PMID 17900695). Every number on this page is threshold-dependent: change the acuity cut-off, the attribution rule, or whether post-surgical eyes count as "cataract", and the estimate moves.

Definitions that control the numbers

Term Operational definition used in the cited sources
Blindness Presenting visual acuity <3/60 in the better eye, or visual field <10° around fixation (PMID 33275949)
Moderate/severe vision impairment (MSVI) Presenting acuity <6/18 to ≥3/60 in the better eye (PMID 33275949)
Mild vision impairment Presenting acuity ≥6/18 and <6/12 (PMID 33275950)
Cataract blindness (survey) Blindness for which lens opacity is the assigned principal cause; assignment rules differ between surveys
"Any cataract" (prevalence surveys) Frequently includes post-surgical (aphakic/pseudophakic) eyes — e.g. the Chinese meta-analysis (Song 2018, PMID 29977532)
Cataract surgical rate (CSR) Operations per million population per year — an output measure, not a needs measure (Yan 2019, PMID 30362287)
Cataract surgical coverage (CSC) Proportion of people needing surgery who have had it
Effective CSC (eCSC) CSC restricted to those with a good postoperative outcome (McCormick 2022, PMID 36240806)

Presenting versus best-corrected acuity matters most in cataract because the residual refractive error of an unoperated or operated eye is often correctable. In the Chinese meta-analysis, pooled cataract-blindness prevalence in middle-aged and older adults was 2.30% (95% CI 1.72–3.07) at BCVA <0.05, 2.56% (1.94–3.38) at BCVA <0.10, and 4.51% (3.53–5.75) at presenting VA <0.10 — the same population, nearly a doubling of the estimate (PMID 29977532).

Global counts and their uncertainty

Estimate Value (interval) Basis Source
Cataract blindness, ≥50 y, 2020 15.2 M (12.7–18.0) GBD hierarchical model, cause-attributed PMID 33275949
Cataract MSVI, ≥50 y, 2020 78.8 M (67.2–91.4) same PMID 33275949
Cataract blindness, all ages, 2020 17.0 M (39.6% of blindness) cataract-specific meta-analysis 2000–2020 PMID 38461217
Cataract MSVI, all ages, 2020 83.5 M (28.3% of MSVI) same PMID 38461217
All-cause blindness, 2020 43.3 M (37.6–48.4) GBD PMID 33275950
All-cause MSVI, 2020 295 M (267–325) GBD PMID 33275950
Projected all-cause blindness, 2050 61.0 M (52.9–69.3) GBD forecast PMID 33275950
Cataract blindness, 2020 (earlier VLEG model) 13.4 M (3.3–31.6) projected Global Vision Database, 1990–2020 model PMID 29032195

The 2017 and 2024 Vision Loss Expert Group models disagree by several million because they use different data cut-offs, different age scopes and different attribution handling; the wide 80% uncertainty intervals in the earlier model (cataract blindness 2015: 12.6 M, 3.4–28.7) are the honest expression of how sparse population-based cause data are (PMID 29032195). These estimates should be presented side by side and never averaged.

The paradox: falling rates, rising counts

Age-standardised prevalence of cataract blindness fell 27.5% between 1990 and 2020 while the number of cataract-blind people rose 29.7% and the number with cataract MSVI rose 93.1% (PMID 38461217). The mechanism is arithmetic, not clinical failure: population growth plus population ageing add more people to the high-risk age bands each year than surgical capacity removes. The same signature appears in the WHA Global Action Plan assessment — age-standardised avoidable blindness fell 15.4% (95% UI −16.8 to −14.3), yet avoidable-blindness case counts rose 10.8% (8.9–12.4) and avoidable-MSVI counts rose 31.5% (30.0–33.1) (PMID 33275949). Any programme evaluated on prevalence alone will look successful while the queue grows.

Incidence and progression

Incidence data are far scarcer than prevalence data because they require repeated graded lens photography in a cohort.

Measure Value Population Source
10-y incidence, nuclear cataract 36.0% (men 31.7%, women 39.3%) Blue Mountains Eye Study, ≥49 y PMID 17900695
10-y incidence, cortical cataract 28.0% (men 24.4%, women 30.8%) same PMID 17900695
10-y incidence, PSC 9.1% (men 8.2%, women 9.8%) same PMID 17900695
10-y incidence, cataract surgery 17.8% (men 14.4%, women 20.1%) same PMID 17900695
Mean age at cataract surgery 75.8 y, no sex difference (P = 0.9) same PMID 17900695
Any-type progression ≥0.5 LOCS III units over 1 y ≥1 eye in 54% of subjects aged 33–55 Aravind, India Srinivasan 1997, PMID 9486033

Women had significantly higher incidence than men for nuclear (P = 0.04), cortical (P = 0.007), any cataract (P = 0.0006) and cataract surgery (P = 0.03) after age adjustment (PMID 17900695). The Indian progression data matter for trial design: a 1-year change of ≥0.5 LOCS III units in over half of a middle-aged sample implies that intervention studies there could be powered with ~600 subjects over 2 years (PMID 9486033).

Prevalence rises steeply and monotonically with age. In the Chinese meta-analysis, prevalence of any cataract (post-surgical cases included) rose from 6.71% (95% CI 5.06–8.83) in men aged 45–49 to 73.01% (65.78–79.2) at 85–89, and from 8.39% (6.36–10.98) to 77.51% (71.00–82.90) in women (PMID 29977532). Roughly two-thirds of people older than 80 are affected in US estimates, with US cataract numbers projected to reach 50 million by 2050 and >3.5 million operations performed annually (Chen 2025, PMID 40227658).

Regional concentration

Region Finding Source
South Asia Cataract's share of age-standardised blindness (62.9%) exceeds the global figure PMID 38461217
Southeast Asia and Oceania Cataract share 47.9% PMID 38461217
East Asia Cataract leading cause of blindness (43.6%); cataract + URE ≈ 57% of all blindness Cheng 2020, PMID 31462416
Central/South Asia Age-standardised blindness in ≥50 y, 2015: 3.72% (men), 4.00% (women) Nangia 2019, PMID 30409914
Arab countries Pooled severe VI 4.0% (95% CI 2.49–5.51), blindness 4.65% (3.26–6.04), 28 studies Alsolami 2025, PMID 40633432
Indigenous populations worldwide Systematic review found consistently higher visual-loss burden than non-indigenous comparators Foreman 2018, PMID 29596691
Hungary (RAAB) Age/sex-adjusted CSC at VA<3/60 = 90.0%; good visual outcome after surgery in only 79.5%, ocular comorbidity the main cause of poor outcome (78.1%) Sándor 2020, PMID 32309181
Palestine CSR 2,117 operations per million (2015); phaco 73.4% overall but 67% of government-centre operations were ECCE Maswadi 2022, PMID 34121602

The Hungarian result is the general lesson in miniature: high coverage does not imply high effective coverage, because outcome quality is a separate axis (PMID 32309181).

Sex, education and the equity gradient

Women bear 60% of cataract blindness and 59% of cataract MSVI globally (PMID 38461217). This is not fully explained by longevity: pooled across 148 RAAB surveys, eCSC was higher in men than women, risk difference 3.2% (95% CI 2.3–4.1), risk ratio 1.20 (1.15–1.25) (PMID 36240806). In India, eCSC pooled from 31 districts was 36.7% (95% CI 33.6–39.9) versus CSC 57.3% (53.3–61.2) — a relative quality gap of 36.0% — with eCSC rising from 31.0% in illiterate participants to 59.7% in those educated to class 10, and rural residence, older age and eastern/north-eastern residence independently associated with worse eCSC (Gupta 2024, PMID 38622863). Among children with bilateral non-traumatic cataract in low-income countries, the proportion of operated children who were girls was below the gender-neutral reference (Gilbert 2016, PMID 26992842).

Childhood cataract

Childhood cataract is rare and poorly enumerated. Across 20 prevalence and 4 incidence studies from five geographical regions, prevalence of childhood cataract ranged 0.32–22.9 per 10,000 children (median 1.03) and congenital cataract 0.63–9.74 per 10,000 (median 1.71); incidence 1.8–3.6 per 10,000 per year. Prevalence was 0.42–2.05 per 10,000 in low-income economies versus 0.63–13.6 in high-income economies, and no difference by laterality or sex was detected (Sheeladevi 2016, PMID 27518543). The lower apparent prevalence in low-income economies is very likely ascertainment, not biology — the review's own conclusion is that the epidemiological base is inadequate. See congenital and paediatric cataract.

Service volume and economic burden

Cataract surgical rate tracks development rather than need: CSR correlated with Human Development Index (R² = 49.2%, β = 5.01, P < 0.001) and GDP per capita (R² = 38.9%, β = 0.56, P < 0.001), and the global inequality in CSR stayed roughly stable over the period studied (PMID 30362287). Reported CSRs span 36 to 12,800 per million population, and average CSC in most countries reviewed was around 50% or lower (Hashemi 2025, PMID 39638415).

The economic literature is skewed toward the countries with least unmet need: of 155 regional cost estimates in a systematic review of the economics of vision impairment, 103 (66%) came from high-income countries, and reported average cataract surgery cost per patient ranged $54–$3,654 purchasing-power-parity — variation driven as much by costing method as by real resource use (Marques 2022, PMID 35340626). Cost-utility of first-eye surgery ranged $245–$22,000/QALY in Western countries and $9–$1,600/QALY in developing countries, comparable to hip arthroplasty and generally better than knee arthroplasty or defibrillator implantation; the Cataract Surgery Affordability Index varied 17–189% in developed and 29–133% in developing countries relative to the United States (Lansingh 2007, PMID 17383730).

The measurement target has changed

Because prevalence and counts diverge, the global indicator moved from a prevalence-reduction target to a coverage-and-quality target: the 74th World Health Assembly endorsed a 30-percentage-point increase in effective cataract surgical coverage by 2030, with eCSC and effective refractive error coverage chosen as the tracking indicators for universal health coverage in eye care (Keel 2021, PMID 34237266). Modelled from 233 population-based survey datasets in 68 countries, global eCSC at the 6/18 threshold was 48.2% (39.7–57.2) in 2025 and is predicted to rise 8.4 percentage points (8.1–8.6) between 2020 and 2030, from 43.9% to 52.3% — roughly a quarter of the target — with country estimates ranging from 2.1% (95% CI 0.9–3.4) in Burundi in 2024 to 77.7% (72.9–82.5) in Qatar in 2023 (McCormick 2026, PMID 41687671). Uncorrected refractive error accounted for a median 26.4% of non-good postoperative outcomes per survey, and correcting it alone was estimated to raise eCSC at the 6/12 threshold by a median 3.7 percentage points (PMID 41687671). The commentary literature has begun to say plainly that the field is falling short (Wiedemann 2026, PMID 42382972).

Regional prevalence work adds the risk-factor context that global models omit. A review of 29 European studies in Caucasian populations aged 40–95 quantified associations with former smoking (RR 3.75, 95% CI 2.26–6.21), current smoking (2.34, 1.07–5.15), diabetes of more than 10 years' duration (2.72, 1.72–4.28) and long-term corticosteroid use (3.25, 1.39–7.58 for oral use beyond five years) (Prokofyeva 2013, PMID 22715900); a classic methodological review argued that cataract does not fit a single-exposure model at all and that undernutrition is the alterable factor with the best combination of coherence and predictive performance (Hodge 1995, PMID 8654515). Those exposures are treated in risk factors.

Reading these numbers safely

  • Person-level and eye-level denominators are not interchangeable. Blindness is a person-level outcome defined on the better eye; complications and prediction error are eye-level.
  • Attribution is a judgement. In eyes with cataract and AMD or glaucoma, cause assignment differs between surveys and shifts cataract's share.
  • Post-surgical eyes are sometimes counted as "cataract". Prevalence figures including operated eyes measure lifetime disease, not current burden (PMID 29977532).
  • Age-standardised and crude trends can move in opposite directions and routinely do here (PMID 38461217).
  • CSR ≠ CSC ≠ eCSC. Only eCSC contains outcome information (PMID 36240806).

Open questions

  • How much of the female excess in cataract blindness is incidence versus access? Both components are documented separately — higher age-adjusted incidence in women (PMID 17900695) and lower eCSC in women (PMID 36240806) — but no analysis has decomposed the global 60% female share into longevity, incidence and coverage contributions (PMID 38461217).
  • What would harmonised opacity thresholds do to burden estimates? Prevalence varies roughly two-fold with the acuity threshold within a single population (PMID 29977532); the burden models have never been re-run under a single harmonised definition to show how much of the between-model disagreement is definitional.
  • Is childhood cataract prevalence genuinely lower in low-income economies? The measured range is lower (0.42–2.05 vs 0.63–13.6 per 10,000) yet the review attributes this to ascertainment gaps rather than biology (PMID 27518543); no population-based study with active case-finding has settled it.
  • Does CSR growth translate into eCSC growth? CSR is strongly predicted by HDI and GDP (PMID 30362287), but the relationship between rising CSR and rising effective coverage has not been measured longitudinally in any country.

References

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  2. GBD 2019 Blindness and Vision Impairment Collaborators, Vision Loss Expert Group of the Global Burden of Disease Study. Causes of blindness and vision impairment in 2020 and trends over 30 years, and prevalence of avoidable blindness in relation to VISION 2020: the Right to Sight: an analysis for the Global Burden of Disease Study. The Lancet. Global health. 2021;9:e144-e160. PMID 33275949
  3. Vision Loss Expert Group of the Global Burden of Disease Study, GBD 2019 Blindness and Vision Impairment Collaborators. Global estimates on the number of people blind or visually impaired by cataract: a meta-analysis from 2000 to 2020. Eye (London, England). 2024;38:2156-2172. PMID 38461217
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