Table 1 Study characteristics of all included studies

Abdullah,1965 [12]

UK

Not described

≥ 65

Male 26.5%

Female 73.5%

3 patient groups - geriatric patients in London hospital; those of similar age seen on domiciliary visits; those attending a local social club. Moderately representative.

Unclear. 79 or 103

Not described

General VI

Cataract

Ability to read or not

Not described

Amjad, 2019 [13]

USA

Cross-sectional

≥65;

Mean: 82.3 ± 8.1

Male 41.6%

Female 59.4%

Community dwelling adults participating in 2011 NHATS (population- based nationally representative cohort of Medicare beneficiaries aged 65+), who died by 2015. Highly representative

542

Based on algorithm: clinician diagnosis of dementia or AD; AD-8 dementia screening interview of proxy respondents

VI

Based on interview questions including: ‘Uses corrective lenses or blind’, ‘Sees well enough to recognize person across street’, ‘Can watch TV across room’, ‘Reads newspaper print’

Bayer, 2002 [14]

Germany

Case-control

With glaucoma;

Mean: 72.9 ± 10.6

Without glaucoma

Mean: 71.4 ± 11.9

Male 35.7%

Female 64.3%

4 nursing homes in Upper Bavaria, Germany. Low representativeness

112

Based on criteria for probable dementia based on NINCDS-ADRDA

Glaucoma

Visual field defects and/or optic disk cup-to-disk ratio of 0.8 or greater with an optic nerve head appearance consistent with glaucoma. Eye exams performed by one of the investigators.

Bayer, 2002 [15]

Germany

Case- control

With glaucoma; mean: 71.9 ± 11.6 Without glaucoma mean: 73.2 ± 12.3^a

Male 38.8%

Female 61.2%

2 nursing homes in Upper Bavaria, Germany. Low representativeness

49

Not described

Glaucoma

Visual field defects and/or optic disk cup-to-disk ratio of 0.8 or greater with an optic nerve head appearance consistent with glaucoma. Eye exams performed by two investigators.

Bennett, 2018 [16]

UK

Cohort study

Not described

Not described

Randomly sampled from primary care list in 3 areas of England. CFAS I, with an 80% response rate, CFAS II, with a 56% response rate. Highly representative.

83 in CFAS I and 277 in CFAS II.

Diagnosis via

an algorithm

VI

Self-reported with no further details.

Bowen, 2016 [17]

UK

Cross-sectional

60–89

Male 37.9%

Female 62.1%

Recruited from 20 NHS sites in six English regions. Includes both those in the community and nursing homes. Participation rate not reported but 100 withdrew (12.4%). Highly representative.

708 (VA measured in only 588)

Known diagnosis of dementia. Unclear how this data was obtained.

VI

Visual acuity (logMAR) worse than 6/12 or worse than 6/18 measured before and after refraction as assessed by an optometrist.

Or Blindness – VA of < 3/60 in the better eye with presenting correction (ICD-10,12 categories 3–5) or visual field of no greater than 10 degrees in radius around central fixation.

AMD

AMD was classified into dry and wet (neovascular) AMD and then graded as mild, moderate or severe. Based on medical records and optometrist exam.

Cataract

Cataract sufficient to be graded on the TOC cataract grading scale. Based on medical records and optometrist exam.

Diabetic Retinopathy

Based on medical records and optometrist exam

Glaucoma

Based on medical records and optometrist exam

Bowen, 2016 [17]

UK

Qualitative

60–89

Male

50%;

Female

50%

Purposive sampling from community setting and based on those who participated in the prevalence study above. Low representativeness.

36

Unclear how this data was obtained.

VI

Visual acuity (logMAR) worse than 6/12 or worse than 6/18 measured before and after refraction as assessed by an optometrist.

Or Blindness – VA of < 3/60 in the better eye with presenting correction (ICD-10,12 categories 3–5) or visual field of no greater than 10 degrees in radius around central fixation.

AMD

AMD was classified into dry and wet (neovascular) AMD and then graded as mild, moderate or severe. Based on medical records and optometrist exam.

Cataract

Cataract sufficient to be graded on the TOC cataract grading scale. Based on medical records and optometrist exam.

Diabetic Retinopathy

Based on medical records and optometrist exam

Glaucoma

Based on medical records and optometrist exam

Carcenac, 2009 [18]

Canada

Cross-sectional

Not described

Not described

Nursing home setting. Only includes those who have died between April 2000 and April 2004. Not representative as only includes those who have died.

228

Not described. Extracted from clinical files of deceased patients.

AMD;

Glaucoma

Based on clinical files of deceased patients.

Chandra, 1986 [19]

USA

Case-control

Mean: 80.1

Male 40.6%

Female 59.4%

Community setting. Only includes those who have died (as dementia status is based on cause of death). Not representative.

7195

Listed as cause of death

Cataract Glaucoma Blindness

Listed on death certificate

Chriqui, 2017 [20]

Canada

Cross-sectional

≥ 65; Range 68 to 102; Mean: 87.2 ± 7.5

Male 26.7%;

Female

73.3%

Residents of nursing homes. Populations of these facilities are representative of community nursing homes in the US. Response/completion rate of 50.8%. Moderately representative for nursing home setting.

150

Diagnosis recorded in medical chart.

VI

Distance VA lower than 6/12 (0.30 logMAR 20/40) in the better seeing eye as assessed by an optometrist.

Chung, 2015 [21]

Taiwan

Case-control

≥45;

Mean 76.8 ± 9.6

Male 45.2%

Female 54.8%

1,000,000 individuals randomly sampled from the Registry for Beneficiaries (n = 23.72 million) of the Taiwan National Health Insurance (NHI) program. Highly representative as most people in Taiwan are covered by the NHI.

7770

Diagnosis of dementia on claims records with ICD-9 codes. At least one diagnosis made by certified neurologist or psychiatrist.

Glaucoma

Based on ICD-9 codes in claims data.

Clague, 2017 [22]

UK

Cross-sectional

Mean: 82.6 ± 7.4;

Male 29.4%

Female 70.6%

All registered patients who were alive and permanently registered in the Primary Care Clinical Informatics Unit with 314 general practices on 31 March 2007. Representative sample of the Scottish population. Highly representative.

10,528

Diagnosis from electronic medical records

Blindness or low vision

Identified open angle glaucoma cases by the principal diagnosis of ICD-9-CM codes 365.1, 365.10, or 365.11 in a medical claim during ambulatory care visits.

Deardorff, 2019 [23]

USA

Cross-sectional

≥65

Not described

Community-dwelling Medicare beneficiaries, enrolled in the MCBS between 1999 and 2006. Highly representative.

871

Self-report

VI

Based on question: How much trouble do you have with your vision? (no trouble, little trouble, or a lot of trouble). Subjects who reported “little trouble” or “a lot of trouble” were classified as having VI.

Frost, 2016 [24]

Australia

Case-control

Mean: 70.2 ± 9.0

Male 59%

Female 41%

Community setting. Recruited from AIBL study in Western Australia (a study of over 2000 people with long-term follow up over 10 years). Moderately representative

22

NINCDS-ADRDA criteria for probable AD.

AMD

Retinal photos reviewed by experienced grader from Centre for Eye Research plus categorized as AMD based on software

Hamedani, 2019 [25]

USA

Cross-sectional

Not described

Not described

Community setting. Medicare database includes 97% of those aged 65+ in US (47,582,342 beneficiaries). Highly representative.

Not described

ICD-9 in claims data

Blindness or low vision

Blindness/low vision was defined by ICD-9 diagnosis codes (369.0–369.4) in claims data.

Heun, 2013 [26]

UK

Case-control

Mean 85.1 ± 8.2;

Male 34.9% Female 65.1%

Based on hospital register so likely included all patients meeting criteria during a defined period but unclear. Low representativeness.

634

ICD-10 codes in hospital discharge data

Glaucoma

ICD-10 codes in hospital discharge data

John, 1999 [27]

UK

Case-control

Mean 84.7 (Range 73.6–96.4)

Male 33.3%

Female 66.7%

Community setting. Sample of 500 older persons from Oxfordshire in the UK. Low representativeness.

79

Port-mortem diagnosis established by consortium.

Cataract

Based on medical records from annual physical and neurological assessments

Kang, 2012 [28]

USA

Cross-sectional

≥ 60

Male 35.3%;

Female

64.7%

17 Nursing homes in Iowa. 10 participants from each NH randomly selected from list of residents with dementia. Refusal rate of 10%. Highly representative of nursing home setting.

153

Diagnosis of AD or other dementia in medical chart

VI

Assessed by MDS section D1 Vision questionnaire.

Kiely, 2018 [29]

Australia

Cross-sectional

≥65; range 73 to 79; Mean: 75.3 ± 1.5

Male 62.5%

Female 37.5%

Sampled from wave four of the oldest cohort of the PATH study, a representative community-based longitudinal cohort commencing in 2001 with follow-up every four years. Highly representative.

64

DSM-IV criteria for dementia or 5th Edition criteria for major neurocognitive disorder

VI

Impaired VA defined as > 0.3 logMAR (worse than 20/40 or 6/12) as assessed by a trained interviewer

Kosse, 2015 [30]

Netherlands

Cross-sectional

Not described

Male 60%

Female 40%

Residents living in a 20-bed closed psychogeriatric ward in nursing home between September 2011 and April 2013. Low representativeness.

20

Extracted from electronic medical records.

Visual problems

Extracted from electronic medical records.

Lai, 2017 [31]

Taiwan

Case-control

≥45;

Mean 78.7 ± 6.6

Male 42.6%

Female 57.4%

Database of NHI. People 65+ with ICD-9 diagnosis of AD in 2000–2011 + 4 controls for each AD case. Highly representative as most people in Taiwan are covered by the NHI.

1351

ICD-9 codes listed on insurance claims for 2 or more visits

Glaucoma

ICE-9 codes in medical claims data for 2 or more visits.

Lawrence, 2009 [9]

UK

Qualitative

65–99

Male 36.8%

Female 63.2%

Participants drawn from 4 socially and ethnically diverse south London boroughs. Highly representative.

19

Using a dementia service OR using a vision service + the “MMBlind”, the “Short Form of the Informant Questionnaire of Cognitive Decline in the Elderly” and the CDR scale

VI

Assessed with Snellen acuity and Seeing Severity Scale.

Löppönen, 2004 [32]

Finland

Cross-sectional

Mean 82.4 ± 7

Male 32%

Female 68%

Community sample. 12% of the population in Lieto was invited. Participation rate of 82%. Highly representative.

112

Clinical assessment and DSM-IV + NINDS-AIREN for vascular dementia

Cataract

Glaucoma

ICD-10 code in medical records.

Luo, 2018 [33]

China

Cross-sectional

Not described

Male 38.6%

Female 52.5%

Data from Second National Samples Survey on Disability from April to May 31,2006. Covers all provincial administrative areas in Mainland China. Highly representative.

1208

Combination of self-report and on-site diagnosis by psychiatrist according to ICD-10.

VI

Used WHO criteria but limited to VI due to uncorrectable causes. Assessed by ophthalmologist.

Marquie, 2019 [34]

Spain

Cross-sectional

Mean age 81.4 ± 7.2.

Male 31.6%

Female 69.4%

Recruited from public memory clinic; program that assesses cognition in community for free without referral; and a cohort study. Response rate 96.3%. Moderately representative.

833

Clinical diagnosis based on DSM-IV

Glaucoma

AMD

Low VA

High IOP

Based on examination by an optometrist

Morse, 2004 [35]

USA

Cross-sectional

Mean: 84

Not described

Randomly selected from 11 New York city long-term-care facilities. Highly representative.

391

Not described

VI

Normal VA = 20/20–20/40; mild VI 20/50–20/70; moderate VI 20/80–20/200; severe VI 20/250–20/1000, very severe VI = counting fingers, hand motion, or no light perception. Assessed by Vistech Consultant.

Muurinen, 2014 [36]

Finland

Cross-sectional

> 65;

Mean: 83

Male 22%

Female 78%

All permanent residents in assisted living facilities in two cities in 2007. 70% participation rate. Moderately representative.

833 (1398)

Not described

VI

Based on answer to question “Is the resident’s vision good enough for reading regular print” yes/no (with or without glasses). Response of no = VI. Reported from trained nurses who knew the residents well.

Nyman, 2017 [37]

UK

Qualitative

Mean: 82.1; Range: 58–96

Male

34.6%

Female

65.4%

Not described

26

Has received a formal diagnosis of dementia or has been referred for/in the process of receiving dementia assessment.

VI

Certified as having VI, registered blind or partially sighted, or self-reported low vision.

Patel, 2019 [38]

USA

Cross-sectional

≥ 65

Not described

Recruited from 2011 to 2016 from the NHATS, a nationally representative survey of 11,558 Medicare enrollees age ≥ 65. Highly representative.

Not described

Unclear but based on tests of memory, orientation and executive function

VI

Difficulty recognizing someone across the street. Self- reported with no further details.

Pelletier, 2014 [39]

Canada

Case-control

Mean 83.7 ± 6.3; Range: 66–101

Male 29.6% Female 71.4%

Recruited people with dementia from 2 academic hospitals, admitted from April 2008 to April 2009. Highly representative.

220

Clinical diagnosis with DSM-IV criteria. Had to have received diagnosis either before or during admission.

Glaucoma

Based on medical records or use of medication

Prince, 2011 [40]

China, India, Cuba, Dominican Republic, Venezuela, Mexico, Peru

Cross-sectional

≥ 65

More females than males in all sites

All residents aged 65+ in 11 geographically defined sites in seven LAMIC (India, China, Cuba, Dominican Republic, Venezuela, Mexico and Peru). Highly representative.

Not described

Diagnosis based on meeting either 10/66 or DSM-IV criteria.

VI

Eyesight problems which result in at least some difficulty, and/or an observer-rated item by the interviewer of ‘near total blindness’

Smilnak, 2019 [41]

USA

Case-control

≥ 75

Mean age 88.6 ± 5.9

Male 33.9%

Female 66.1%

Pathologic specimens of eyes and brains of autopsy subjects aged 75 and above who presented to Duke University Medical Center. Low representativeness as only includes those who have died.

115

Autopsy and pathological diagnosis

AMD Glaucoma (severe)

Autopsy and histopathological diagnosis.

Tamura, 2006 [42]

Japan

Case- control

Mean: 80.9 ± 8.4

Male 17.2%

Female 82.8%

Institutionalized residents or those accessing treatment at 4 hospitals. Highly representative.

172

Diagnosis of probable AD was based on

clinical findings according to NINCDS-ADRDA

Glaucoma

Probable OAG was diagnosed by width of the angle of the anterior chamber >grade 2, a vertical cup-to-disc ratio of the optic nerve head > 0.7 and/or difference between the vertical cup-to-disc ratio in the eyes > 0.2 with characteristic glaucomatous disc change. Ophthalmic examination was performed and diagnosis was made by two glaucoma specialists

Varadaraj, 2020 [43]

USA

Cross-sectional

> 65;

Not described

Recruited form the NHATS, a nationally representative survey of Medicare beneficiaries aged 65 years and older. Highly representative.

Not described

Diagnosis of probable dementia based on (a) participant- or proxy-reported physician diagnosis of dementia or AD, or (b) an AD8 score ≥ 2; or (c) participant cognitive test scores ≤1.5 SDs below mean in at least two of the three cognitive domains. Possible dementia based on cognitive test scores ≤1.5 SDs below mean in one domain in the absence of meeting the physician diagnosis or AD8 criteria described above.

VI

Vision impairment was defined as self-reported blindness or difficulty with distance/near vision

Williams, 2014 [44]

UK

Case-control

Mean 80.1 ± 7.7

Male 36.8%

Female 63.2%

Opportunistic rather than consecutive recruitment of cases to a primary care clinic. Low representativeness.

258

Clinical examination and NINCDS criteria

AMD

Based on photos and Wisconsin AMD grading system.

Wittich, 2019 [45]

Canada

Cross-sectional

Not described

Not described

Not described

21

Clinical diagnosis by consensus. Specific clinical criteria used are not described.

Reduced visual acuity

Reduced reading acuity (MNRead) (> .5 logMAR [20/63]). Moderate to severe loss of contrast sensitivity (Mars test) (<  1.48 log CS [3.3% contrast]).

Wong, 2015 [46]

Singapore

Cross-sectional

>  60

Not described

Recruited from 3 tertiary hospitals. Consecutive recruitment from July 2009 to December 2012. Moderately representative.

268 (outcome data on only 264)

DSM-IV criteria

AMD Diabetic retinopathy Cataract Glaucoma

Retinal photographs reviewed by ophthalmologist