Rapid Assessment of Avoidable Blindness and Diabetic Retinopathy in Chiapas, Mexico

doi:10.1016/j.ophtha.2011.11.002

Ophthalmology

Volume 119, Issue 5, May 2012, Pages 1033-1040

https://doi.org/10.1016/j.ophtha.2011.11.002 Get rights and content

Objective

To estimate the prevalence and causes of blindness in Chiapas, Mexico, and to assess the feasibility of using the Rapid Assessment of Avoidable Blindness framework to estimate diabetic retinopathy (DR) prevalence.

Design

A cross-sectional population-based survey.

Participants

Sixty-six clusters of 50 people 50 years of age or older were selected by probability proportionate to size sampling. Households within clusters were selected through compact segment sampling.

Methods

Participants underwent visual acuity (VA) screening and diagnosis of cause of visual impairment by an ophthalmologist. Participants were classed as having diabetes if they had a previous diagnosis of diabetes, were receiving treatment for glucose control, or had a random blood glucose level of more than 200 mg/dl. Participants with diabetes were assessed for DR using dilated clinical examination (direct and indirect ophthalmoscope) and 1 dilated digital fundus photograph per eye (graded by an ophthalmologist during the survey and regraded by a retinal specialist—“reference standard”) following the Scottish DR grading protocol.

Main Outcome Measures

Prevalence of blindness (VA <20/400 in the best eye with available correction) and DR.

Results

Three thousand three hundred subjects were selected, of whom 2864 (87%) were examined. The estimated prevalence of bilateral blindness was 2.3% (95% confidence interval [CI], 1.7%–2.9%). Cataract was the leading cause of bilateral blindness (63%), followed by posterior segment diseases (24%), which included DR (8% of blindness). The prevalence of diabetes was 21% (19.5%–23.1%). Among participants with diabetes, the prevalence of DR (in at least 1 eye) was 38.9% (95% CI, 33.7%–44.1%). The prevalence of sight-threatening DR (STDR; defined as proliferative DR, referable maculopathy, or both) was 21.0% (95% CI, 16.7%–25.3%). Agreement with the reference standard was good for any retinopathy and STDR for the clinical examination (κ = 0.80 and 0.79, respectively) and the photograph graded during the survey (κ = 0.80 and 0.82, respectively).

Conclusions

The prevalence of diabetes and DR in Chiapas was high. Including the DR component was possible, but added considerably to the cost and complexity of the survey, and so would be warranted only if a high prevalence of diabetes is expected and if resources and time permit.

Financial Disclosure(s)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Section snippets

Rapid Assessment of Avoidable Blindness

This study was undertaken in the Central, Highland, and Frialesca regions of Chiapas, Mexico, from January through April 2010. A required sample size of 3600 was estimated based on expected prevalence of blindness of 3% among adults 50 years of age or older, a required confidence of 95%, a precision of 25%, design effect of 1.5, and a 10% nonresponse rate. In total, 66 clusters of 50 people 50 years of age or older were included.

Clusters were selected using probability proportionate to size

Study Population

Of 3300 eligible survey participants, 2864 (87%) took part in the RAAB, 293 (9%) were not available, 127 (4%) declined, and 16 (0.5%) were unable to communicate. Compared with census data, there was a slight underrepresentation of men, particularly in the younger age group (50–59 years), in the study sample.

Prevalence and Causes of Visual Impairment

The sample prevalence of bilateral blindness (VA <20/400 with available correction) was 2.3% (95% confidence interval [CI], 1.7%–2.9%; Table 2). The prevalence of bilateral severe visual

Discussion

This was the first study to pilot test the inclusion of DR in RAAB—a commonly used blindness survey tool—and, to the best of the authors' knowledge, is the first population-based survey of DR in Mexico for 19 years.⁸ The prevalence of bilateral blindness in adults 50 years of age or older was 2.3%, and cataract was the leading cause of bilateral blindness (63%), followed by posterior segment diseases (24%). The prevalence of diabetes was high at 21%, and this was particularly marked in urban

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National sex- and age-specific burden of blindness and vision impairment by cause in Mexico in 2019: a secondary analysis of the Global Burden of Disease Study 2019
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Using public data from the Global Burden of Disease (GBD) study 2019, we present national prevalence and years lived with disability (YLDs) counts and crude and age-standardized rates (per 100,000 people) of total, severity- and cause-specific blindness and vision impairment with 95% uncertainty intervals (UIs) by sex and age group.
In Mexico, the burden of blindness and vision impairment was estimated at 11.01 million (95% UI, 9.25–13.11) prevalent cases and 384.96 thousand (259.57–544.24) YLDs during 2019. Uncorrected presbyopia caused the highest burden (6.06 million cases, 4.36–8.08), whereas severe vision loss and blindness affected 619.40 thousand (539.40–717.73) and 513.84 thousand (450.59–570.98) people, respectively. Near vision loss and refraction disorders caused 78.7% of the cases, whereas neonatal disorders and age-related macular degeneration were among the least frequent. Refraction disorders were the main cause of moderate and severe vision loss (61.44 and 35.43%), and cataracts were the second most frequent cause of blindness (26.73%). Females suffered an overall higher burden of blindness and vision impairment (54.99% and 52.85% of the total cases and YLDs), and people >50 years of age suffered the highest burden, with people between 70 and 74 years being the most affected.
Vision loss represents a public health problem in Mexico, with women and older people being the most affected. Although the causes of vision loss contribute differentially to the severity of visual impairment, most of the impairment is avoidable. Consequently, a concerted effort at different levels is needed to alleviate this burden.
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Diagnostic Accuracy of Rapid Assessment of Avoidable Blindness: A Population-based Assessment
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Citation Excerpt :
The standard RAAB protocol was modified in some RAAB surveys to arrive at a more refined diagnosis. After that, some studies reported that a modified approach to detect DR was added to RAAB surveys conducted in Mexico33 and Saudi Arabia.34 In these studies, participants with a previous diagnosis of diabetes or a random blood glucose level of more than 200 mg/dL were assessed for DR using dilated direct and indirect ophthalmoscopy examination and digital fundus photography.
To evaluate the diagnostic accuracy of rapid assessment of avoidable blindness (RAAB).
Population-based diagnostic accuracy study.
A total of 2145 (95.3%, 2145/2250) subjects aged 50 years and older who participated in the RAAB survey were included. All the recruited participants underwent ophthalmic examination according to the RAAB protocol and then were reexamined with instruments in a mobile eye clinic set up in a village center on the same day. Examination in the mobile clinic included standardized visual acuity (VA) tests using logMAR charts, refraction, slit-lamp biomicroscopy, and dilated fundal examination with a binocular indirect ophthalmoscope. Blindness and economic blindness were defined as VA in the better-seeing eye <3/60 and <6/60, respectively. Visual impairment (VI) was defined as VA <6/18 in the better eye. The primary cause of blindness and VI was defined according to the cause of VI in the participant's better eye. Main Outcome Measures: The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and area under the curve (AUC) of receiver operating characteristics of RAAB for detection of blindness and the principal causes of VI.
A total of 1816 subjects (84.7%), including 686 men (37.8%) and 1130 women (62.2%), underwent ophthalmic examination in the mobile eye clinic. The mean (±standard deviation) age was 64.4 ± 9.6 years. The sensitivities, specificities, AUC, PLR, and NLR of RAAB were 90.3%, 99.3%, 0.948, 124.0, and 0.10, respectively, for detection of blindness (presenting visual acuity, PVA <3/60); 89.5%, 98.7%, 0.940, 69.2, and 0.11, respectively, for detection of economic blindness (PVA <6/60); and 90.3%, 97.7%, 0.940, 38.7, and 0.10, respectively, for detection of VI (PVA <6/18). The sensitivities, specificities, AUC, PLR, and NLR were 90.5%, 98.1%, 0.943, 48.1, and 0.10; and 60.4%, 98.7%, 0.796, 46.4, and 0.40 for detection of VI (PVA <6/18) owing to cataract and refractive error, respectively.
The diagnostic performances of RAAB were high for detecting the prevalence of blindness, VI, and VI owing to cataract.
Adults visual impairment and blindness – An overview of prevalence and causes in Saudi Arabia
2019, Saudi Journal of Ophthalmology
Citation Excerpt :
Recently, Saudi Arabia has experienced major socio-economic developments that positively support the national plan for the elimination of trachoma in Saudi Arabia by 2019.13 In contrast, the proportion of blindness and MSVI due to diabetic retinopathy (DR) is rapidly growing from 1986 to 2015 which becoming a serious health problem in Saudi Arabia as it was reported in other NAME countries and globally.28,29,30,31,32 The reported prevalence of DR among diabetics in Saudi Arabia is close to the global estimate (36% versus 34.6%) respectively.33
A major socio-economic development in Saudi Arabia affected the pattern and causes of visual impairment for the past 40 years. Moreover, an up-to-date summary of available data is vital for planning, monitoring, and evaluating national blindness prevention program.
This study conducted to provide a summary overview of prevalence, causes, and changes in the pattern of blindness and visual impairment for the past 40 years among Saudi adults, with brief discussion of the related socio-economic and ecological factors.
The review was confined to the published epidemiological studies performed in Saudi Arabia covering the age group 18 year and older from 1985 onwards.
Six epidemiological studies were included from 1985 onwards. In1986, the prevalence of blindness and visual impairment in Saudi Arabia were 1.5% and 7.8%, respectively which is 20 times the magnitude of blindness in the United States. Multiple regional population based studies conducted later in areas with disparate ecological and socio-economical determinants at different time intervals showed variable prevalence of blindness 3.3% Eastern Province 1986, 0.7% Bisha 1993. Recently, in older than 50 year population the reported prevalence was 2.6% Taif 2012 and 5.7% Jazan 2015 and 6.4% in Ahsa. Since 1986, the single leading cause of adult blindness in Saudi Arabia is cataract. Although, Trachoma reported to be the second primary cause of blindness on 1986, its burden is reduced in Jizan (2015) and minimal in Taif (2012) which is replaced by chronic diseases related etiologies i.e Diabetic Retinopathy.
Ecological and socio-economical determinants play critical role in the magnitude and causes of blindness and visual impairment in Saudi Arabia. Significant data gaps obscure monitoring and evaluation of the eye health. Eye health indicators should be integrated into the national health information system for dynamic monitoring and evaluation.
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Prevalence and incidence of diabetic retinopathy in patients with diabetes of Latin America and the Caribbean: A systematic review and meta-analysis
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View all citing articles on Scopus

: Manuscript no. 2011-838.

: Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

: Supported by grants from Fight for Sight, London, United Kingdom; and CBM, Bensheim, Germany. The funding organizations had no role in the design or conduct of this research.

View full text

Original articleRapid Assessment of Avoidable Blindness and Diabetic Retinopathy in Chiapas, Mexico

Objective

Design

Participants

Methods

Main Outcome Measures

Results

Conclusions

Financial Disclosure(s)

Section snippets

Rapid Assessment of Avoidable Blindness

Study Population

Prevalence and Causes of Visual Impairment

Discussion

Ophthalmology

Ophthalmology

Ophthalmology

Am J Ophthalmol

Ophthalmology

Ophthalmology

Ophthalmology

Ophthalmology

Ophthalmology

IDF Diabetes Atlas

Global prevalence of diabetes: estimates for the year 2000 and projections for 2030

Diabetes Care

Global data on visual impairment in the year 2002

Bull World Health Organ

Leading causes of certification for blindness and partial sight in England & Wales

BMC Public Health [serial online]

Prevalence of diabetic retinopathy in urban India: the Chennai Urban Rural Epidemiology Study (CURES) eye study, I

Invest Ophthalmol Vis Sci

Diabetic retinopathy and risk of blindness in Mexico: are we doing enough?

Diabetes Care

Diabetic retinopathy in Mexico: prevalence and clinical characteristics

Arch Med Res

Rapid assessment of avoidable blindness

Community Eye Health

Original article
Rapid Assessment of Avoidable Blindness and Diabetic Retinopathy in Chiapas, Mexico