Self-adjustable glasses in the developing world

Approaches for delivery of refractive and optical care services in community and primary care settings

BACKGROUND

Uncorrected refractive error is a leading cause of vision impairment which, in most cases, can be managed with the appropriate spectacle correction. In 2021, the World Health Assembly endorsed a global target of a 40-percentage-point increase in effective coverage of refractive error by 2030. To achieve this global target, equitable access to refractive and optical services within community and primary care settings needs to be strengthened. This review will inform the development of technical guidance to support improvements in the testing and correction of refractive error among World Health Organization (WHO) member states.

OBJECTIVES

To determine the range of approaches for delivery of refractive and optical care services in community and primary care settings, and the methods employed for their evaluation.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and Global Health databases, grey literature, and annual reports and websites of relevant organizations involved in eye-care delivery from January 2002 to November 2022 to identify approaches for refractive and optical service delivery.

SELECTION CRITERIA

We included observational and interventional studies, reviews, and reports from relevant organizations related to delivering refractive services and optical services for preschool and school-aged children and adults in community and primary care settings published between January 2002 and November 2022. We searched for studies and reports published within the last 20 years because vision impairment due to uncorrected refractive error has only recently become a public health and eye health priority, therefore we did not expect to find much relevant literature until after 2002.

DATA COLLECTION AND ANALYSIS

Two review authors screened titles, abstracts and full texts, and extracted data. We resolved any discrepancies through discussion. We synthesized data, and presented results as tables, figures, and case studies. This project was led by the World Health Organization (WHO) Vision and Eye Care Programme.

MAIN RESULTS

We identified 175 studies from searches of databases and grey literature, 146 records from company reports, and 81 records from website searches of relevant organizations that matched our inclusion criteria. Delivery approaches for refractive and optical services in community care included school-based, pharmacy, and outreach models, whereas primary care approaches comprised vision centre, health centre, and a combination of vision or health centre and door-to-door delivery. In community care, school-based and outreach approaches were predominant, while in primary care, a vision-centre approach was mainly used. In the WHO African region, the school-based and outreach approaches were mainly reported while, in the Americas, the outreach approach was mostly used. Very few approaches for service delivery were reported in the WHO Eastern Mediterranean region. Prominent gaps exist in the evaluation of the approaches, and few studies attempted to evaluate the approaches for delivery of refractive and optical care services.

AUTHORS' CONCLUSIONS

We comprehensively describe a range of approaches for delivery of refractive and optical services in community and primary care. Further evaluation of their effectiveness will better inform the application of these service-delivery approaches. The study outcomes will help guide WHO member states in strengthening refractive and optical services at community and primary care levels.

FUNDING

This scoping review was supported by the Vision and Eye care Programme, World Health Organization and ATscale Global Partnership.

REGISTRATION

The protocol of this scoping review was published in the Open Source Framework.

The association between objective vision impairment and mild cognitive impairment among older adults in low- and middle-income countries

AIM

The association between visual impairment and mild cognitive impairment (MCI) has not been investigated to date. Thus, we assessed this association among older adults from six low- and middle-income countries (LMICs) (China, India, Ghana, Mexico, Russia, and South Africa) using nationally representative datasets.

METHODS

Cross-sectional, community-based data from the WHO Study on global AGEing and adult health (SAGE) were analyzed. Visual acuity was measured using the tumbling ElogMAR chart, and vision impairment (at distance and near) was defined as visual acuity worse than 6/18 (0.48 logMAR) in the better-seeing eye. The definition of MCI was based on the National Institute on Aging-Alzheimer's Association criteria. Multivariable logistic regression was conducted.

RESULTS

Data on 32,715 individuals aged ≥ 50 years [mean (SD) age 62.1 (15.6) years; 51.2% females] were analyzed. Compared to those without far or near vision impairment, those with near vision impairment but not far vision impairment (OR = 1.33; 95% CI = 1.16-1.52), and those with both far and near vision impairment (OR = 1.70; 95% CI = 1.27-2.29) had significantly higher odds for MCI. Only having far vision impairment was not significantly associated with MCI.

CONCLUSIONS

Visual impairment is associated with increased odds for MCI among older adults in LMICs with the exception of far vision impairment only. Future longitudinal and intervention studies should examine causality and whether improvements in visual acuity, or early intervention, can reduce risk for MCI and ultimately, dementia.

Prevalence of Refractive Error and Visual Impairment among Rural Dwellers in Mashonaland Central Province, Zimbabwe

Purpose

To determine the prevalence of refractive error and visual impairment in a rural population of Zimbabwe.

Methods

This community-based, cross-sectional study used a multi-stage sampling to select the participants from households in four communities within three rural districts in Mashonaland Central Province. Participants' demographic data were collated, and their presenting visual acuity (VA) was measured using the logMAR E chart. Clinical refraction was preceded by an anterior segment and posterior segment eye examinations. Visual impairment was defined as presenting VA worse than 6/12 (0.3 logMAR) in the better eye. Descriptive statistics were presented as frequencies.

Results

A total of 519 participants were involved in this study. Their ages ranged from 5 to 100 years (mean age = 50.94; standard deviation ± 21.12 years). Out of the 519 participants, 233 (44.9%) were male, and 286 (55.1%) were female. The prevalence of visual impairment was 56.8% (95% confidence interval [CI]: 55.7-67.2), and blindness was 13.1% (95% CI: 11.2-17.6). The prevalence of near visual impairment based on presenting near VA (N = 408) was 78.6% (95% CI: 78.1-85.4). The two most common causes of visual impairment were uncorrected refractive errors (UREs) (54.2%) and cataract (24.8%). The most common cause of blindness was cataract (41.2%). Hypermetropia (56.9%) was the most common refractive error.

Conclusions

A high burden of visual impairment due to UREs and cataracts was observed among the rural dwellers of Zimbabwe. Public health education, access to refractive error services, and cataract surgery are necessary to mitigate this high burden of visual impairment.

Comparison of self-refraction using a simple device, USee, with manifest refraction in adults

Background

The USee device is a new self-refraction tool that allows users to determine their own refractive error. We evaluated the ease of use of USee in adults, and compared the refractive error correction achieved with USee to clinical manifest refraction.

Methods

Sixty adults with uncorrected visual acuity <20/30 and spherical equivalent between –6.00 and +6.00 diopters completed manifest refraction and self-refraction.

Results

Subjects had a mean (±SD) age of 53.1 (±18.6) years, and 27 (45.0%) were male. Mean (±SD) spherical equivalent measured by manifest refraction and self-refraction were –0.90 D (±2.53) and –1.22 diopters (±2.42), respectively (p = 0.001). The proportion of subjects correctable to ≥20/30 in the better eye was higher for manifest refraction (96.7%) than self-refraction (83.3%, p = 0.005). Failure to achieve visual acuity ≥20/30 with self-refraction in right eyes was associated with increasing age (per year, OR: 1.05; 95% CI: 1.00–1.10) and higher cylindrical power (per diopter, OR: 7.26; 95% CI: 1.88–28.1). Subjectively, 95% of participants thought USee was easy to use, 85% thought self-refraction correction was better than being uncorrected, 57% thought vision with self-refraction correction was similar to their current corrective lenses, and 53% rated their vision as “very good” or “excellent” with self-refraction.

Conclusion

Self-refraction provides acceptable refractive error correction in the majority of adults. Programs targeting resource-poor settings could potentially use USee to provide easy on-site refractive error correction.

Self-assessment of refractive errors using a simple optical approach

Background

This explorative study investigated procedures for the self‐assessment of spherocylindrical refractive errors.

Methods

Eighteen participants with a mean age of 34.0 ± 8.8 years were enrolled. Adjustable Alvarez lenses were mounted in a rotatable ring holder and two procedures were tested for the self‐adjustment: (1) rotation of the lens in three meridians: 0°, 60° and 120° and (2) rotation of the optotypes in the same meridians. Starting from maximum positive power, the participants were required to decrease the power of the Alvarez lens until the optotypes (0.0 logMAR) appeared to be clear the first time. Best‐corrected visual acuity (BVA) was measured using a psychophysical staircase procedure. Bland–Altmann analysis was carried out in order to calculate the limits of agreement between the self‐refraction method and the standard subjective refraction.

Results

Using procedure 1, 77 per cent of the subjects achieved a VA ≥ 0.1 logMAR (6/7.5) and the same was true for 88 per cent of the subjects using procedure 2. Using procedure 1, a significantly worse BVA was found, when compared to subjective refraction (ΔVA = −0.15 logMAR, F_3,140 = 7.11, p = 0.046, median test). Analysis of variance (ANOVA) analysis showed a significant influence of the refraction method on the oblique astigmatism component J₄₅ but not for the spherical equivalent M and the straight astigmatism component J₀ (M: F_3,140 = 0.532, p = 0.661; J₀: F_3,140 = 0.056, p = 0.983; J₄₅: F_3,140 = 13.97, p < 0.001; ANOVA). The limits of agreement for the spherical equivalent error M were ± 1.10 D and ± 1.20 D and for the astigmatic components J₀ ± 0.78 D and ± 0.59 D and for J₄₅ ± 0.62 D and ± 0.54 D, for procedure 1 and procedure 2, respectively.

Conclusions

Fixed adjustable Alvarez lenses and rotatable stimuli can provide a fast and precise self‐assessment method to measure the spherocylindrical error of the eye.

Vision Stations: Addressing Corrective Vision Needs With Low-cost Technologies

Eyeglasses, required for functional vision by nearly half the world's population, are still needed by more than a billion people. There are a number of constraints on the provision of eyeglasses: product cost, durability, and appearance; traditional approaches to evaluating refraction; and sustainably scaling potential distribution methods. We offer our experience with an immigrant population in a US urban setting using a "Vision Station." The station allowed for immediate provision of adjustable glasses using self-refraction, ordering of custom lenses from a low-cost website, and referral to primary and eye care physicians for those with medical eye concerns. As with models in development by other groups, Vision Stations connect people with the life-changing provision of functional vision.