Quality of eyeglass prescriptions from a low-cost wavefront autorefractor evaluated in rural India: results of a 708-participant field study

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.

Uncorrected Refractive Error in the African American Eye Disease Study

Importance

Refractive error remains the largest cause of correctable visual impairment in the US. Correction of refractive error will reduce visual impairment and its associated morbidity but also improve quality of life and productivity.

Objective

To determine the burden of and risk factors (RFs) associated with any uncorrected refractive error (UCRE) and unmet refractive need (URN) in a population-based sample of African American adults.

Design, Setting, and Participants

This cross-sectional study, conducted from April 2014 to April 2018, included a population-based sample of self-identified African American participants 40 years and older from 30 contiguous census tracts in Inglewood, California. Participants underwent a complete ophthalmic examination and an in-home-administered questionnaire to assess sociodemographic, lifestyle, biological, medical, and health care and eye care usage RFs associated with UCRE and URN. Measurements of visual acuity (VA) were performed using a standard Early Treatment Diabetic Retinopathy Study protocol. Noncycloplegic automated refraction with supplemental subjective refraction was performed. UCRE was defined as an improvement of 2 or more lines with refraction in the better-seeing eye. URN was defined as an improvement of 2 or more lines with refraction in the better-seeing eye in those persons who were visually impaired. Sex- and age-specific burden of UCRE and URN were calculated, and multiple regression analyses were used to identify independent RFs. Study data were analyzed from May 2018 to December 2023.

Exposures

Presence or absence of correctable refractive error.

Main Outcomes and Measures

Self-reported sex- and age-specific prevalence of and risk indicators of UCRE and URN.

Results

Of the 7957 eligible participants in the African American Eye Disease Study (AFEDS), 6347 (80%) completed both the in-home interview and the clinical examination. Of these, 6337 participants (mean [SD] age, 61 [11] years; 3997 female [63%]) with complete refractive error data were included in the analysis. Refractive error-related correctable visual impairment was present in over two-thirds of participants with visual impairment (68.7%). The overall prevalence of any UCRE was 14.6% (925 of 6337), and the overall prevalence of any URN was 5.4% (URN1 [those with presenting VA of worse than 20/40 in the better-seeing eye but who could achieve 20/40 or better with correction], 157 of 2893; URN2 [those with presenting VA of worse than 20/40 in the better-seeing eye but who could achieve an improvement of 2 or more lines with refractive correction], 155 of 2891).

Conclusions and Relevance

Results of this cross-sectional study suggest a high burden of refractive error-associated correctable refractive error in African American adults, making it the leading cause of visual impairment in this population. Providing universal coverage for vision care and prescription glasses is an affordable and achievable health care intervention that could reduce the burden of visual impairment in African American adults by over two-thirds and likely raise the quality of life and work productivity, especially in this vulnerable minority population.

Quality of Refractive Error Care in Cambodia: An Unannounced Standardized Patient Study

PURPOSE

Quality-of-care in refractive error services is essential, as it directly affects vision outcomes, wellbeing, educational attainment, and workforce participation. In Cambodia, uncorrected refractive error is a leading cause of mild and moderate vision impairment in adults. We evaluated the quality of refractive error care in Cambodia by estimating the proportion of prescribed and dispensed spectacles appropriate for people's refractive error needs and factors associated with spectacle quality.

METHODS

A cross-sectional protocol was employed with 18 Khmer-speaking adult participants observing testing procedures in 156 optical services across six provinces in 2022. A total of 496 dispensed spectacles were assessed against spectacle quality indicators.

RESULTS

The analysis revealed that 35.1% of dispensed spectacles were of optimal quality. The most common error observed in sub-optimal spectacles was the presence of horizontal prism outside of tolerance limits. The study also found that 44.0% of emmetrope visits involved unnecessary prescription spectacle recommendations, and 18.3% of written prescriptions did not correspond with dispensed spectacles. Sex differences were observed, with men predominantly providing refractive error care and women more likely to be unnecessarily recommended prescription spectacles.

CONCLUSION

The findings highlight the importance of prioritizing quality-of-care in refractive error services. A key recommendation is to consider regulatory mechanisms to ensure optical services employ appropriately qualified staff. Additionally, efforts should be made to eliminate unnecessary prescriptions -- especially for emmetropes and females -- standardize written prescriptions, ensure consistent pupil distance measurements, reduce reliance on autorefraction, and address the gender imbalance in the refractive error workforce.

Auto-refraction versus subjective refraction in different phakic and pseudophakic conditions: the Tehran Geriatric Eye Study (TGES)

AIM

To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions.

METHODS

This report is a part of the Tehran Geriatric Eye Study (TGES) that was conducted from January 2019 to January 2020 on elderly population 60 years of age and above in Tehran. The samples were selected by multi-stage stratified random cluster sampling. Of 3791 individual invitees, 3310 (response rate: 87.3%) participated in this study. All study participants underwent non-cycloplegic auto-refraction (auto-refractometer/keratometer Nidek ARK-510) and subjective refraction.

RESULTS

Regarding the sphere, eyes with mixed cataract had the worst limits of agreement (LoA: -1.24 to 0.87) and the best agreement was related to the pseudophakic eyes (LoA: -0.83 to 0.54). The highest (0.27±0.31 D) and lowest (0.21±0.27 D) differences between the two methods regarding the cylinder power were observed in eyes with cortical cataract and normal eyes, respectively. The worst LoA between the two methods in measuring the cylinder power was related to the eyes with mixed cataract (LoA: -0.44 to 0.96). Regarding the J0 (horizontal/vertical components of astigmatism), the mean values of J0 obtained by auto-refraction were tended more toward against the rule direction in all crystalline lens conditions, and the two methods had the greatest difference in cortical cataract cases (0.05±0.17 D). Regarding the J45 (oblique components of astigmatism), the lowest (0±0.11 D) and highest (-0.01±0.12 D) differences were observed in normal eyes and eyes with cortical cataract, respectively.

CONCLUSION

The auto-refractometer/keratometer Nidek ARK-510 results in the elderly with different phakic and pseudophakic conditions do not correspond well with subjective refraction findings. This discrepancy in spherical findings is more pronounced in individuals with mixed cataract than in other cases.

Accuracy of a low-cost, portable, refractive error estimation device: Results of a diagnostic accuracy trial

Purpose

To assess the accuracy of refraction measurements by ClickCheck^TM compared with the standard practice of subjective refraction at a tertiary level eye hospital.

Design

Diagnostic accuracy trial.

Methods

All participants, recruited consecutively, underwent auto-refraction (AR) and subjective refraction (SR) followed by refraction measurement using ClickCheck^TM (CR) by a trained research assistant. Eyeglass prescriptions generated using ClickCheck^TM and the resulting visual acuity (VA) was compared to SR for accuracy. Inter-rater reliability and agreement were determined using Intra-class correlation and Bland Altman analysis respectively.

Results

The 1,079 participants enrolled had a mean (SD) age of 39.02 (17.94) years and 56% were women. Overall, 45.3% of the participants had refractive error greater than ±0.5D. The mean (SD) spherical corrections were -0.66D (1.85) and -0.89D (2.20) in SR and CR respectively. There was high level of agreement between the spherical power measured using SR and CR (ICC: 0.940 (95% CI: 0.933 to 0.947). For the assessment of cylindrical correction, there was moderate level of agreement between SR and CR (ICC: 0.493 (0.100 to 0.715). There was moderate level of agreement between the VA measurements performed by using corrections from SR and CR (ICC: 0.577 (95% CI: 0.521–0.628). The subgroup analysis based on the age categories also showed high level of agreement for spherical corrections between the two approaches (ICC: 0.900). Bland Altman analysis showed good agreement for spherical corrections between SR and CR (Mean difference: 0.224D; 95% LoA: -1.647 D to 2.096 D) without evidence of measurement bias.

Conclusions

There was a high level of agreement for spherical power measurement between CR and SR. However, improvements are needed in order to accurately assess the cylindrical power. Being a portable, low-cost and easy-to-use refraction device, ClickCheck^TM can be used for first level assessment of refractive errors, thereby enhancing the efficiency of refractive services, especially in low- and-middle-income countries.

Prediction of manifest refraction using machine learning ensemble models on wavefront aberrometry data

PURPOSE

To assess the performance of machine learning (ML) ensemble models for predicting patient subjective refraction (SR) using demographic factors, wavefront aberrometry data, and measurement quality related metrics taken with a low-cost portable autorefractor.

METHODS

Four ensemble models were evaluated for predicting individual power vectors (M, J0, and J45) corresponding to the eyeglass prescription of each patient. Those models were random forest regressor (RF), gradient boosting regressor (GB), extreme gradient boosting regressor (XGB), and a custom assembly model (ASB) that averages the first three models. Algorithms were trained on a dataset of 1244 samples and the predictive power was evaluated with 518 unseen samples. Variables used for the prediction were age, gender, Zernike coefficients up to 5th order, and pupil related metrics provided by the autorefractor. Agreement with SR was measured using Bland-Altman analysis, overall prediction error, and percentage of agreement between the ML predictions and subjective refractions for different thresholds (0.25 D, 0.5 D).

RESULTS

All models considerably outperformed the predictions from the autorefractor, while ASB obtained the best results. The accuracy of the predictions for each individual power vector component was substantially improved resulting in a ± 0.63 D, ±0.14D, and ±0.08 D reduction in the 95% limits of agreement of the error distribution for M, J0, and J45, respectively. The wavefront-aberrometry related variables had the biggest impact on the prediction, while demographic and measurement quality-related features showed a heterogeneous but consistent predictive value.

CONCLUSIONS

These results suggest that ML is effective for improving precision in predicting patient's SR from objective measurements taken with a low-cost portable device.

Predicting subjective refraction with dynamic retinal image quality analysis

The aim of this work is to evaluate the performance of a novel algorithm that combines dynamic wavefront aberrometry data and descriptors of the retinal image quality from objective autorefractor measurements to predict subjective refraction. We conducted a retrospective study of the prediction accuracy and precision of the novel algorithm compared to standard search-based retinal image quality optimization algorithms. Dynamic measurements from 34 adult patients were taken with a handheld wavefront autorefractor and static data was obtained with a high-end desktop wavefront aberrometer. The search-based algorithms did not significantly improve the results of the desktop system, while the dynamic approach was able to simultaneously reduce the standard deviation (up to a 15% for reduction of spherical equivalent power) and the mean bias error of the predictions (up to 80% reduction of spherical equivalent power) for the handheld aberrometer. These results suggest that dynamic retinal image analysis can substantially improve the accuracy and precision of the portable wavefront autorefractor relative to subjective refraction.

Investigation of the Accuracy of a Low-Cost, Portable Autorefractor to Provide Well-Tolerated Eyeglass Prescriptions: A Randomized Crossover Trial

PURPOSE

To compare patient preferences for eyeglasses prescribed using a low-cost, portable wavefront autorefractor versus standard subjective refraction (SR).

DESIGN

Randomized, cross-over clinical trial.

PARTICIPANTS

Patients aged 18 to 40 years presenting with refractive errors (REs) to a tertiary eye hospital in Southern India.

METHODS

Participants underwent SR followed by autorefraction (AR) using the monocular version of the QuickSee device (PlenOptika Inc). An independent optician, masked to the refraction approach, prepared eyeglasses based on each refraction approach. Participants (masked to refraction source) were randomly assigned to use SR- or AR-based eyeglasses first, followed by the other pair, for 1 week each. At the end of each week, participants had their vision checked and were interviewed about their experience with the eyeglasses.

MAIN OUTCOME MEASURES

Patients preferring eyeglasses were chosen using AR and SR.

RESULTS

The 400 participants enrolled between March 26, 2018, and August 2, 2019, had a mean (standard deviation) age of 28.4 (6.6) years, and 68.8% were women. There was a strong correlation between spherical equivalents using SR and AR (r = 0.97, P < 0.001) with a mean difference of -0.07 diopters (D) (95% limits of agreement [LoA], -0.68 to 0.83). Of the 301 patients (75.2%) who completed both follow-up visits, 50.5% (n = 152) and 49.5% (n = 149) preferred glasses prescribed using SR and AR, respectively (95% CI, 45.7-56.3; P = 0.86). There were no differences in demographic or vision characteristics between participants with different preferences (P > 0.05 for all).

CONCLUSIONS

We observed a strong agreement between the prescriptions from SR and AR, and eyeglasses prescribed using SR and AR were equally preferred by patients. Wider use of prescribing based on AR alone in resource-limited settings is supported by these findings.

Does the Accuracy and Repeatability of Refractive Error Estimates Depend on the Measurement Principle of Autorefractors?

Purpose

The purpose of this study was to determine the accuracy and repeatability of refractive errors obtained using three autorefractors based on different measurement principles, vis-à-vis, gold-standard retinoscopy.

Methodology

Accuracy of noncycloplegic, sphero-cylindrical refractive error of 234 eyes was obtained using the rotary prism-based RM-8900 closed-field autorefractor, photorefraction based Spot vision screener, wavefront aberrometry based E-see, and streak retinoscopy by four different examiners, masked to the results of each other. Intersession repeatability of autorefractors was determined by repeat measurements in a subset of 40 subjects.

Results

Retinoscopy values of M, J₀, and J₄₅ power vectors for the cohort ranged from -10.2 to 8 D, -1.4 to 1.8 D, and -0.9 to 1.2 D, respectively. Across autorefractors, the interequipment bias of M and J₀ power vectors were statistically insignificant (< ±0.5 D; P > 0.05) but the corresponding limits of agreement were ±2.5 and ±1 D, respectively, without any trend across instruments or the patient's age (P > 0.5). Repeatability of M and J₀ power vectors were ±0.75 D and ±0.40 D, respectively, across autorefractors. The range of J₄₅ power vector was too narrow for any meaningful analysis.

Conclusions

Refractive errors measured using autorefractors operating on different principles show minimal bias and good short-term repeatability but relatively large agreement limits, vis-à-vis, retinoscopy. Among them, the wavefront aberrometry based E-see autorefractor performs relatively better in all measurement parameters evaluated here.

Translational Relevance

Although autorefractor estimates of noncycloplegic refractive error appears independent of their measurement principle, their relatively poor agreement with gold-standard retinoscopy warrants caution while used for screening and quantification of refractive errors.

Assesment of the QuickSee wavefront autorefractor for characterizing refractive errors in school-age children

Purpose

To assess the performance of an open-view binocular handheld aberrometer (QuickSee) for diagnosing refractive errors in children.

Methods

123 school-age children (9.9 ± 3.3 years) with moderate refractive error underwent autorefraction (AR) with a standard desktop device and subjective refraction (SR), with or without cycloplegia to determine their eyeglass prescription. Measurements with QuickSee (QS) were taken in 62 of these patients without cycloplegia (NC), and in 61 under cycloplegia (C). Differences in refraction values (AR vs SR vs QS) as well as the visual acuity (VA) achieved by the patients with each method (QS vs SR) were used to evaluate the performance of the device in measuring refractive error.

Results

The spherical equivalent refraction obtained by QS agreed within 0.5 D of the SR in 71% (NC) and 70% (C) of the cases. Agreement between the desktop autorefractor and SR for the same threshold was of 61% (NC) and 77% (C). VA resulting from QS refractions was equal to or better than that achieved by SR procedure in 77% (NC) and 74% (C) of the patients. Average improvement in VA with the QS refractions was of 8.6 and 13.4 optotypes for the NC and C groups respectively, while the SR procedure provided average improvements of 8.9 (NC) and 14.8 (C) optotypes.

Conclusions

The high level of agreement between QuickSee and subjective refraction together with the VA improvement achieved in both study groups using QuickSee refractions suggest that the device is a useful autorefraction tool for school-age children.

Better one or two? A systematic review of portable automated refractors

INTRODUCTION

More than 400 million people suffer from visual impairment globally, with more than half due to uncorrected refractive error. Autorefraction (AR) is the most common examination performed prior to prescribing glasses. As technology advances, so has the accuracy and number of portable autorefractors available. Portable technology has become acutely important with the coronavirus disease 2019 pandemic and the conversion of in-person clinical evaluations to remote telemedicine encounters. Patients and providers want to do as much as possible remotely. The aim of this study was to conduct a systematic literature review of the accuracy and effectiveness of available portable automated refractors compared to the current standard of care, subjective refraction (SR).

METHODS

A literature search of PubMED, Embase and ClinicalTrials.gov 97 unique publications in English on portable autorefractors. Twelve studies comparing a portable AR device to at least one form of SR were systematically included in this review.

RESULTS

There were four portable autorefractors (Netra, Quicksee, Retinomax and SVOne) studied against SR. There was high patient acceptance of glasses prescriptions by the Quicksee alone, with 87% subjects seeing the same or better than SR. Quicksee was more accurate than Netra and Retinomax. SVOne was preferred over Netra and outperformed Retinomax in multiple measures, despite Retinomax being the fastest test.

DISCUSSION

There are numerous portable autorefractors available, but few were compared against SR. Quicksee and SVOne are the most accurate and patient-preferred devices. Quicksee was the most accurate, and it performed clinically the same as SR in some reports.

Diffuser-based computational imaging funduscope

Poor access to eye care is a major global challenge that could be ameliorated by low-cost, portable, and easy-to-use diagnostic technologies. Diffuser-based imaging has the potential to enable inexpensive, compact optical systems that can reconstruct a focused image of an object over a range of defocus errors. Here, we present a diffuser-based computational funduscope that reconstructs important clinical features of a model eye. Compared to existing diffuser-imager architectures, our system features an infinite-conjugate design by relaying the ocular lens onto the diffuser. This offers shift-invariance across a wide field-of-view (FOV) and an invariant magnification across an extended depth range. Experimentally, we demonstrate fundus image reconstruction over a 33° FOV and robustness to ±4D refractive error using a constant point-spread-function. Combined with diffuser-based wavefront sensing, this technology could enable combined ocular aberrometry and funduscopic screening through a single diffuser sensor.

Accuracy of the Hand-held Wavefront Aberrometer in Measurement of Refractive Error

Purpose

To compare refractive error measured by hand-held wavefront aberrometers with postcycloplegic autorefraction (AR) and cycloplegic refraction (CR).

Methods

The medical records of patients who received refractive measurements using the wavefront aberrometer, postcycloplegic AR, and CR between January 2014 and January 2016 were retrospectively analyzed. The mean differences, 95% confidence intervals, and limits of agreement (LOA) were calculated for the refractive vector components (M, J₀, and J₄₅).

Results

Fifty-one patients (9.0 ± 5.5 years, male 41.2%) were enrolled in this study, and only the right eye of each was included. Refractive errors ranged from −9.25 to +7.25 diopters (D) for spherical equivalent (median, 0.75 D). The M component was not significantly different among the three methods (p = 0.080). However, the J₀ vector component was significantly different (p < 0.001). After post hoc analysis, the wavefront aberrometer obtained more positive values for J₀ compared to the other methods. The J₄₅ component was not significantly different among the three methods (p = 0.143). The mean difference between the wavefront aberrometer and postcycloplegic AR was −0.115 D (LOA, −1.578 to 1.348 D) for M, 0.239 D (LOA, −0.371 to 0.850 D) for J₀, and −0.015 D (LOA, −0.768 to 0.738 D) for J₄₅. The mean difference between the wavefront aberrometer and CR was −0.220 D (LOA, −1.790 to 1.350 D) for M, 0.300 D (LOA, −0.526 to 1.127 D) for J₀, and −0.079 D (−0.662 to 0.504 D) for J₄₅.

Conclusions

The wavefront aberrometer showed good agreement with postcycloplegic AR and CR in spherical equivalents, but tended to produce slightly myopic results. The wavefront aberrometer also overestimated with-the-rule astigmatism. Therefore, we recommend that the device be used for estimations of refractive error, which may be useful for patients who have postural difficulties, live in undeveloped countries, or are bedridden.

Holographic waveguide based optometer for the quantitative monitoring of ocular refractive error

Oculomotor disorders are known to have profound impacts on a patients' quality of life. However, current clinical practice lacks the capability to provide simultaneous assessment of three tightly coupled oculomotor control components, i.e. eye movement, lens accommodation, and pupil response. In this study, a holographic waveguide (HW) based benchtop optometer was constructed and evaluated with a model eye. Experimental result and quantitative analysis indicate that a HW can convey high quality retinal images to a camera at an illumination level safe for human subjects and support high accuracy measurements of ocular refractive error over a wide range. Further development of a HW-based system promises a wearable, see-through device for comprehensive assessment of oculomotor control components while the subject is engaged in normal daily activities and thus enable advanced research and clinical management of oculomotor disorders.