Blindness and visual impairment due to age-related cataract in sub-Saharan Africa: a systematic review of recent population-based studies

Crystalline lens nuclear age prediction as a new biomarker of nucleus degeneration

BACKGROUND

The crystalline lens is a transparent structure of the eye to focus light on the retina. It becomes muddy, hard and dense with increasing age, which makes the crystalline lens gradually lose its function. We aim to develop a nuclear age predictor to reflect the degeneration of the crystalline lens nucleus.

METHODS

First we trained and internally validated the nuclear age predictor with a deep-learning algorithm, using 12 904 anterior segment optical coherence tomography (AS-OCT) images from four diverse Asian and American cohorts: Zhongshan Ophthalmic Center with Machine0 (ZOM0), Tomey Corporation (TOMEY), University of California San Francisco and the Chinese University of Hong Kong. External testing was done on three independent datasets: Tokyo University (TU), ZOM1 and Shenzhen People's Hospital (SPH). We also demonstrate the possibility of detecting nuclear cataracts (NCs) from the nuclear age gap.

FINDINGS

In the internal validation dataset, the nuclear age could be predicted with a mean absolute error (MAE) of 2.570 years (95% CI 1.886 to 2.863). Across the three external testing datasets, the algorithm achieved MAEs of 4.261 years (95% CI 3.391 to 5.094) in TU, 3.920 years (95% CI 3.332 to 4.637) in ZOM1-NonCata and 4.380 years (95% CI 3.730 to 5.061) in SPH-NonCata. The MAEs for NC eyes were 8.490 years (95% CI 7.219 to 9.766) in ZOM1-NC and 9.998 years (95% CI 5.673 to 14.642) in SPH-NC. The nuclear age gap outperformed both ophthalmologists in detecting NCs, with areas under the receiver operating characteristic curves of 0.853 years (95% CI 0.787 to 0.917) in ZOM1 and 0.909 years (95% CI 0.828 to 0.978) in SPH.

INTERPRETATION

The nuclear age predictor shows good performance, validating the feasibility of using AS-OCT images as an effective screening tool for nucleus degeneration. Our work also demonstrates the potential use of the nuclear age gap to detect NCs.

Prevalence of Visual Impairment and Associated Factors Among Older Adults in Southern Ethiopia, 2022

Background

Visual impairment is a functional limitation of the eye brought on by a disorder or disease that can make it more difficult to carry out daily tasks. Visual impairment causes a wide range of public health, social, and economic issues, particularly in developing nations, where more than 90% of the world's visually impaired people reside. Although many studies conducted in Ethiopia related with the topic, there were focused on childhood visual impairments.

Objectives

To assess the prevalence and factors associated with visual impairment among older adults.

Methodology

A community-based cross-sectional study design was conducted in Arba Minch Zuria District. Systematic sampling technique was employed to select 655 adults aged 40 and above. Data were gathered through face-to-face interviews and visual acuity measurements, and SPSS version 25 was used for analysis. Bivariate and multivariate logistic regression analyses were performed to identify factors associated with visual impairment.

Results

The overall prevalence of visual impairment was found to be 36.95% (95% CI=33.2-40.8%). Factors associated with a higher odds of visual impairment included aged 51-60 years (AOR=2.37,95%CI=1.29-4.44), aged 61 and above (AOR=8.9, 95%CI=4.86-16.3), low wealth index ((AOR=1.81, 95%CI: 1.14-3.2), divorced and widowed (AOR=4.67, 95%CI:2.77-7.86), no formal education (AOR=14.28, 95%CI: 2.82-71.46), not utilizing eyeglass (AOR=3.94, 95%CI (1.65-9.40). The most possible causes of visual impairment were found to be refractive error and cataract.

Conclusions and Recommendations

The prevalence of visual impairment among study population was relatively high, and more than three-fifths of participants had unilateral visual impairment. Age, marital status, occupation, educational status, wealth index, and not wearing of prescribed eyeglasses were significantly associated with visual impairment. Refractive error is the leading cause of visual impairment. Awareness of spectacle use and expanding cataract surgery coverage are urgently needed in this area.

Deep Learning Automated Diagnosis and Quantitative Classification of Cataract Type and Severity

PURPOSE

To develop and evaluate deep learning models to perform automated diagnosis and quantitative classification of age-related cataract, including all three anatomical types, from anterior segment photographs.

DESIGN

Application of deep learning models to Age-Related Eye Disease Study (AREDS) dataset.

PARTICIPANTS

18,999 photographs (6,333 triplets) from longitudinal follow-up of 1,137 eyes (576 AREDS participants).

METHODS

Deep learning models were trained to detect and quantify nuclear cataract (NS; scale 0.9-7.1) from 45-degree slit-lamp photographs and cortical (CLO; scale 0-100%) and posterior subcapsular (PSC; scale 0-100%) cataract from retroillumination photographs. Model performance was compared with that of 14 ophthalmologists and 24 medical students. The ground truth labels were from reading center grading.

MAIN OUTCOME MEASURES

Mean squared error (MSE).

RESULTS

On the full test set, mean MSE values for the deep learning models were: 0.23 (SD 0.01) for NS, 13.1 (SD 1.6) for CLO, and 16.6 (SD 2.4) for PSC. On a subset of the test set (substantially enriched for positive cases of CLO and PSC), for NS, mean MSE for the models was 0.23 (SD 0.02), compared to 0.98 (SD 0.23; p=0.000001) for the ophthalmologists, and 1.24 (SD 0.33; p=0.000005) for the medical students. For CLO, mean MSE values were 53.5 (SD 14.8), compared to 134.9 (SD 89.9; p=0.003) and 422.0 (SD 944.4; p=0.0007), respectively. For PSC, mean MSE values were 171.9 (SD 38.9), compared to 176.8 (SD 98.0; p=0.67) and 395.2 (SD 632.5; p=0.18), respectively. In external validation on the Singapore Malay Eye Study (sampled to reflect the distribution of cataract severity in AREDS), MSE was 1.27 for NS and 25.5 for PSC.

CONCLUSIONS

A deep learning framework was able to perform automated and quantitative classification of cataract severity for all three types of age-related cataract. For the two most common types (NS and CLO), the accuracy was significantly superior to that of ophthalmologists; for the least common type (PSC), the accuracy was similar. The framework may have wide potential applications in both clinical and research domains. In the future, such approaches may increase the accessibility of cataract assessment globally. The code and models are publicly available at https://XXX.

Factors associated with delayed uptake of cataract surgery among adult patients at Mulago National Referral Hospital, Uganda

BACKGROUND

Cataract is the leading cause of blindness globally. Many patients with cataract in developing countries delay to come for cataract surgery.

OBJECTIVES

This study aimed to determine the factors associated with delayed uptake of cataract surgery among adult patients seen at Mulago National Referral Hospital eye clinic in Uganda.

METHODS

Employing a hospital based cross-sectional study, adult patients with cataract and having moderate visual impairment or blindness were recruited. Patient-related factors for delayed surgery were assessed using a predetermined questionnaire. Data was analyzed using stata version 14.2. Logistic regressions were used to determine the factors associated with delayed uptake of cataract surgery among these patients.

RESULTS

Eighty two participants with operable cataract were evaluated. Females were 44 (54%) and the mean age of participants was 67 years. Fifty three (65%) had delayed uptake of cataract surgery. The factors associated with delayed uptake of cataract surgery among patients with cataract were financial constraint, felt no need for surgery and good unilateral vision.

CONCLUSIONS

Financial constraints, no felt need for cataract surgery and having good unilateral vision are the factors associated with delayed uptake of cataract surgery among cataract patients. We recommend cataract surgical outreach to remote areas and health education.

Blindness and Visual Impairment Situation in Indonesia Based on Rapid Assessment of Avoidable Blindness Surveys in 15 Provinces

Purpose: To report the latest data on blindness and visual impairment (VI) in Indonesia.Methods: Rapid Assessment of Avoidable Blindness (RAAB) surveys were done in 15 provinces in Indonesia between 2013 and 2017. The population of the study was people aged 50 +. In each province, the required number of clusters was selected with a probability proportionately to size. A weighted average analysis for prevalence, causes of visual impairment, and cataract surgical coverage (CSC) estimated the values of the country.Results: The prevalence of blindness in East Java was the highest at 4.4% (95% CI: 3.1-5.6%), followed by Nusa Tenggara Barat (NTB) at 4.0% (95% CI: 3.0-5.1%) and South Sumatra at 3.4% (95% CI: 2.4-4.4%). In number, blindness among people aged 50+ in East Java was the highest at 371,599, followed by West Java at 180,666 and Central Java at 176,977. Untreated cataract was the commonest cause of blindness in all provinces (range: 71.7% to 95.5%). CSC_person<3/60 and CSC_person<6/60 in Bali were the highest at 81.3% and 72.4%, respectively. Indonesia countrywide prevalence of blindness was 3.0%. The total number of people with VI (PVA less than 6/18 in the better eye) in Indonesia was 8,019,427, consisting of 1,654,595 of blindness and 6,364,832 of moderate and severe VI.Conclusion: The burden of blindness in Indonesia is high, and untreated cataract contributes the most. There is an urgent need to increase cataract surgical coverage by providing better access to cataract surgery services for all people in need.

Incidence of Visually Impairing Cataracts Among Older Adults in Kenya

Importance

Half of all the cases of blindness worldwide are associated with cataract. Cataract disproportionately affects people living in low- and middle-income countries and persons of African descent.

Objective

To estimate the 6-year cumulative incidence of visually impairing cataract in adult participants in the Nakuru Eye Disease Cohort Study in Kenya.

Design, Setting, and Participants

This secondary analysis of the Nakuru Eye Disease Cohort Study was conducted from February 2016 to April 2016. This cohort comprised citizens of Nakuru, Kenya, aged 50 years or older who consented to participate in the initial or baseline survey from January 2007 to November 2008, as well as the follow-up conducted from January 2013 to March 2014. All participants at baseline (n = 4364) and follow-up (n = 2159) underwent ophthalmic examination.

Main Outcomes and Measures

Six-year cumulative incidence of visually impairing cataract, risk factors of incidence, population estimates, and required cataract surgical rates to manage incident visually impairing cataract.

Results

In total, 4364 individuals (with a mean [SD] age of 63.4 [10.5] years and with 2275 women [52.1%]) had complete eye examinations at baseline, and 2159 participants (with a mean [SD] age of 62.5 [9.3] years and with 1140 men [52.8%]) were followed up 6 years later. The 6-year cumulative incidence of visually significant cataract in either eye was 251.9 per 1000 (95% CI, 228.5-276.8), with an increase with age from 128.9 (95% CI, 107.9-153.2) per 1000 for the group aged 50 to 59 years to 624.5 (95% CI, 493.1-739.9) per 1000 for the group aged 80 years or older. This equated to an annual incidence of visually significant cataract of 45.0 per 1000 people aged 50 years or older. Multivariable analysis showed alcohol consumption (risk ratio [RR], 1.4; 95% CI, 1.1-1.8), diabetes (RR, 1.7; 95% CI, 1.3-2.3), educational level, and increasing age (RR, 3.8; 95% CI, 2.6-5.5 for those aged ≥80 years) were associated with incident visually impairing cataract. Extrapolations to all people aged 50 years or older in Kenya indicated that 148 280 (95% CI, 134 510-162 950) individuals might develop new visually impairing cataract in either eye (visual acuity <6/18 in the worse-seeing eye) and that 9540 (95% CI, 6610-13 750) might become cataract blind in both eyes (visual acuity <3/60 in better-seeing eye).

Conclusions and Relevance

Adults in Kenya appeared to have a high incidence of visually impairing cataract, making cataract a priority for blindness prevention programs in the region; surgical interventions and awareness of these services are also required.

Crude and standardized prevalences of cataract and related factors in the elderly people in Northern Iran

Purpose:

This study aims to estimate the crude and standardized prevalences of cataract and its related factors among old people in northern parts of Iran.

Methods:

This cross-sectional study was carried out among 397 people aged 60 and older in northern Iran. Required information about treated and nontreated cataract was collected using a standard checklist. The World Standard Population was applied for direct standardization.

Results:

The standardized prevalence (95% confidence interval) of cataract among men, women, and all people were 27.5% (21.2–33.8), 30.9% (24.5–37.4), and 29.1% (24.6–33.6), respectively. Based on multivariate logistic regression models, age over 75 years (OR = 3.03, 95% CI: 1.21–7.59), living alone (OR = 4.89, 95% CI: 1.86‒12.86), diabetes mellitus (odds ratio = 19.10, 95% confidence interval: 8.13–44.89), rheumatoid arthritis (OR = 7.76, 95% CI: 2.32–25.99), history of infectious diseases (OR = 4.02, 95% CI: 1.35‒11.98), hypertension (OR = 3.19, 95% CI: 1.59–6.42), history of ophthalmic surgery (OR = 2.83, 95% CI: 1.29–6.16), history of sedative drug use (OR = 2.71, 95% CI: 1.35–5.47), history of vitamin supplementation use (OR = 0.21, 95% CI: 0.08–0.55), and familial history of cataract (OR = 2.81, 95% confidence interval: 1.38–5.72) increased the odds of cataract. Our multiple logistic regression model explained 53% of the variation in developing cataract.

Conclusion:

Our study showed that the prevalence of cataract in the study population was relatively high. We also found that aging, living alone, diabetes mellitus, rheumatoid arthritis, hypertension, infectious diseases, ophthalmic surgery, sedative drugs and familial history of cataract were the risk factors of cataract and vitamin supplementations were its protective factors.

Vision loss in Indigenous peoples of the world: a systematic review protocol

REVIEW OBJECTIVE/QUESTION

The objectives of this review are.

Visual impairment and blindness in a population-based study of Mashhad, Iran

Purpose

To determine the prevalence of visual impairment and blindness and related factors in the 1- to 90-year-old urban population of Mashhad.

Methods

In this cross-sectional study of 1- to 90-year-old residents of Mashhad, in northeastern Iran, sampling was done through random stratified cluster sampling (120 clusters). After selecting the samples and their participation in the study, all subjects had vision testing including measurement of visual acuity and refraction, as well as examinations with the slit-lamp and ophthalmoscopy. Visual impairment (primary outcomes) was defined as a visual acuity worse than of 0.5 logMAR (20/60) in the better eye.

Results

Of the 4453 selected persons, 3132 (70.4%) participated in the study. The prevalence of visual impairment based on presenting vision and best-corrected vision was 3.95% (95% confidence interval [CI]: 3.13–4.77) and 2.23 (95% CI: 1.54–2.91), respectively. The prevalence of presenting visual impairment increased from 1.59% in children under 5 years of age to 43.59% in people older than 65 years of age; these figures were respectively 1.59% and 42.31% based on corrected visual acuity. In the logistic regression model, older age (OR = 1.06, 95% CI: 1.04–1.07, P < 0.001), higher education (OR = 0.16, 95% CI: 0.06–0.38, P < 0.001), and low income (OR = 1.36, 95% CI: 1.21–1.72, P < 0.001) correlated with impaired sight. Based on presenting vision and best-corrected vision, the prevalence of blindness was 0.86% (95% CI: 0.51–1.22) and 0.32% (95% CI: 0.1–0.55). The most common causes of visual impairment were uncorrected refractive error (41.8%) and cataract (20%).

Conclusions

According to our findings, the prevalence of visual impairment was intermediate in comparison with other studies. The prevalence of visual impairment in our study was similar to the global average; however, it was markedly high at older ages. Nonetheless, refractive errors and cataracts remain as the main causes of impaired vision and blindness in this population, while these two conditions are easily treatable with correction or surgery.

Investigation of dynamic thiol-disulphide homoeostasis in age-related cataract patients with a novel and automated assay

PURPOSE

The aim of this study was to determine plasma thiol-disulphide homoeostasis in patients with age-related cataract (ARC) and compare the results of the patients with healthy subjects. Plasma malondialdehyde (MDA) levels and catalase (CAT) activity were also investigated.

METHODS

The study included 53 cataract patients and 52 healthy volunteers. Native thiol-disulphide exchanges were determined using a novel and automated method. CAT activity was determined using the method described by Aebi, and MDA levels were calculated using the thiobarbituric acid method.

RESULT

Native thiol and total thiol levels were significantly lower in the cataract patients compared with the controls (p < 0.001, p = 0.002, respectively). The disulphide levels of the cataract patients were significantly higher than the controls (p = 0.002). The ratios of disulphide/native thiol and disulphide/total thiol were statistically higher in the cataract patients compared with the control group (p < 0.001, p < 0.001, respectively). Furthermore, CAT activity was significantly lower in the cataract patient group compared with the control group (p < 0.001), and MDA levels were insignificantly higher in the patient group (p = 0.581).

CONCLUSIONS

Our study showed that dynamic thiol-disulphide homoeostasis has shifted towards disulphide formation, as a result of thiol oxidation in ARC patients. The present study is the first to measure thiol-disulphide homoeostasis in ARC patients with a novel automated assay. This study supports the hypothesis that cataract is an oxidative disorder. Further studies are required in order to examine the relationship between oxidative stress and the development of cataract formation.

Targeted deletion of the murine Lgr4 gene decreases lens epithelial cell resistance to oxidative stress and induces age-related cataract formation

Oxidative stress contributes to the formation of cataracts. The leucine rich repeat containing G protein-coupled receptor 4 (LGR4, also known as GPR48), is important in many developmental processes. Since deletion of Lgr4 has previously been shown to lead to cataract formation in mice, we sought to determine the specific role that Lgr4 plays in the formation of cataracts. Initially, the lens opacities of Lgr4(-/-) mice at different ages without ocular anterior segment dysgenesis (ASD) were evaluated with slit-lamp biomicroscopy. Lenses from both Lgr4(-/-) and wild-type mice were subjected to oxidation induced protein denaturation to assess the ability of the lens to withstand oxidation. The expression of antioxidant enzymes was evaluated with real-time quantitative PCR. Phenotypically, Lgr4(-/-) mice showed earlier onset of lens opacification and higher incidence of cataract formation compared with wild-type mice of similar age. In addition, Lgr4(-/-) mice demonstrated increased sensitivity to environmental oxidative damage, as evidenced by altered protein expression. Real-time quantitative PCR showed that two prominent antioxidant defense enzymes, catalase (CAT) and superoxidase dismutase-1 (SOD1), were significantly decreased in the lens epithelial cells of Lgr4(-/-) mice. Our results suggest that the deletion of Lgr4 can lead to premature cataract formation, as well as progressive deterioration with aging. Oxidative stress and altered expression of several antioxidant defense enzymes contribute to the formation of cataracts.

Sustainable control of onchocerciasis: ocular pathology in onchocerciasis patients treated annually with ivermectin for 23 years: a cohort study

The evolution and persistence of ocular pathology was assessed in a cohort of Onchocerca volvulus infected patients treated annually with ivermectin for 23 years. Patients were resident in rural Central and Kara Region of Togo and ocular examinations included testing of visual acuity, slit lamp examination of the anterior eye segment and the eye fundus by ophthalmoscopy. Before ivermectin treatment, vivid O.volvulus microfilariae (MF) were observed in the right and left anterior eye chamber in 52% and 42% of patients (n = 82), and dead MF were seen in the right and left cornea in 24% and 15% of cases, respectively. At 23 years post initial treatment (PIT), none of the patients (n = 82) presented with MF in the anterior chamber and cornea. A complete resolution of punctate keratitis (PK) lesions without observable corneal scars was present at 23 years PIT (p<0.0001), and sclerosing keratitits (SK) lessened by half, but mainly in patients with lesions at early stage of evolution. Early-stage iridocyclitis diminished from 42%(rE) and 40%(lE) to 13% (rE+lE)(p<0.0001), but advanced iridocyclitis augmented (p<0.001) at 23 years PIT compared to before ivermectin. Advanced-stage papillitis and chorioretinitis did not regress, while early-stage papillitis present in 28%(rE) and 27%(lE) of patients at before ivermectin regressed to 17%(rE) and 18%(lE), and early-stage chorioretinitis present in 51%(rE+lE) of cases at before ivermectin was observed in 12%(rE) and 13%(lE) at 23 years PIT (p<0.0001). Thus, regular annual ivermectin treatment eliminated and prevented the migration of O. volvulus microfilariae into the anterior eye chamber and cornea; keratitis punctata lesions resolved completely and early-stage sclerosing keratitits and iridocyclitis regressed, whilst advanced lesions of the anterior and posterior eye segment remained progressive. In conclusion, annual ivermectin treatments may prevent the emergence of ocular pathology in those populations still exposed to O.volvulus infection.

Trial Registration: www.pactr.orgPACTR201303000464219)