Can Visual Acuity Be Reliably Measured at Home? Validation of Telemedicine Remote Computerised Visual Acuity Measurements

Implementation of anterior segment ophthalmic telemedicine

PURPOSE OF REVIEW

The growing push to integrate telemedicine into ophthalmic practices requires physicians to have a thorough understanding of ophthalmic telemedicine's applications, limitations, and recent advances in order to provide well tolerated and appropriate clinical care. This review aims to provide an overview of recent advancements in the use of ophthalmic telemedicine for anterior segment eye examinations.

RECENT FINDINGS

Virtual care for anterior segment evaluation relies on appropriate technology, novel workflows, and appropriate clinical case selection. Recent advances, particularly in the wake of the COVID-19 pandemic, have highlighted the utility of home-based assessments for visual acuity, external evaluation, tonometry, and refraction. Additionally, innovative workflows incorporating office-based testing into virtual care, termed 'hybrid telemedicine', enable high-quality ophthalmic testing to inform clinical decision-making.

SUMMARY

Novel digital tools and workflows enable high-quality anterior segment evaluation and management for select ophthalmic concerns. This review highlights the clinical tools and workflows necessary to enable anterior segment telehealth.

Evaluating the precision of an online visual acuity test tool

OBJECTIVE

The aim of this study was to assess the precision of a web-based tool in measuring visual acuity (VA) in ophthalmic patients, comparing it to the traditional in-clinic evaluation using a Snellen chart, considered the gold standard.

METHODS

We conducted a prospective and in-clinic validation comparing the Eyecare Visual Acuity Test® to the standard Snellen chart, with patients undergoing both tests sequentially. Patients wore their standard spectacles as needed for both tests. Inclusion criteria involved individuals above 18 years with VA equal to or better than +1 logMar (20/200) in each eye. VA measurements were converted from Snellen to logMAR, and statistical analyses included Bland-Altman and descriptive statistics.

RESULTS

The study, encompassing 322 patients and 644 eyes, compared Eyecare Visual Acuity Test® to conventional methods, revealing a statistically insignificant mean difference (0.01 logMAR, P = 0.1517). Bland-Altman analysis showed a narrow 95% limit of agreement (0.22 to -0.23 logMAR), indicating concordance, supported by a significant Pearson correlation (r = 0.61, P < 0.001) between the two assessments.

CONCLUSION

The Eyecare Visual Acuity Test® demonstrates accuracy and reliability, with the potential to facilitate home monitoring, triage, and remote consultation. In future research, it is important to validate the Eyecare Visual Acuity Test® accuracy across varied age cohorts, including pediatric and geriatric populations, as well as among individuals presenting with specific comorbidities like cataract, uveitis, keratoconus, age-related macular disease, and amblyopia.

Measuring Vision at Home in 2023

Introduction: The ability to measure a patient's visual acuity at home (HVA) is by far the most desired remote telemedicine capability sought by ophthalmologists. Methods: A systematic literature review was done using Pubmed to search for publications from 2010 to 2022 in English reporting on 10 studies that compared a patient's HVA to the clinic visual acuity (CVA). Results: Approaches to measuring HVA included using a phone-based application, a physical chart, a computer, and a website. The most accurate of these was the use of personal computers (COMPlog, Macustat, Web based test) at home with a bias of 1 letter. The most accessible and reliable was the use of a printable visual acuity chart, available in the public domain, which had adifference between HVA and CVA of 1 to 3.5 letters. Phone apps (Verana Vision) and stand-alone websites (Farsight.com) both had a greater mean difference of about 6 letters, respectively,with a moderate correlation coefficient. Discussion: Overall, all three methodologies demonstrated a good negative predictive value demonstrating their potential use as an effective screening tool to flag drastic vision decline between clinic visits.

Evaluation of the Amblyopia tracker app

PURPOSE

The Amblyopia tracker app has been developed to be a tool for parents to monitor changes in vision at home during amblyopia treatment. The aims of this study were to evaluate the feasibility and repeatability of parents testing their children at home and to compare home test results to an assessment in clinic by an orthoptist.

METHODS

Children (age < 18 years) with amblyopia (interocular acuity difference of ≥ 0.2logMAR) were recruited. Parents were asked to test their child with the app three times during a two week period followed by an online questionnaire about the usability. Participants also tested within 48 h of their appointment where the measurement was repeated by an orthoptist.

RESULTS

Out of 277 potential participants contacted, 37 completed three home measurements, mean age 6.8 years (SD 2.94). Home tests comparisons were made between test two and three to ensure familiarity with the process. Paired t-tests showed no statistically significant difference for either eye or the interocular acuity difference (IAD). However, 29% had a difference in IAD of more than 0.1logMAR on repeated testing, with a maximum of 0.4logMAR difference in the IAD. Questionnaire responses from the parents who participated were predominantly positive with 97% of respondents saying they would use it if were available. Comparison of home and clinical measurements (n = 23, mean age 6.72 SD 2.60) showed no statistically significant differences for either eye or interocular acuity difference (paired t-test, p > 0.3 in all cases).

CONCLUSION

Results show no statistically significant differences for the Amblyopia tracker app when used by parents at home on repeated testing, or between the home test by a parent and the test by a clinician. However, variability in the results does indicate that further improvements are required to ensure the results can be used as a reliable clinical tool.

Effect of different screen brightness and devices on online visual acuity test

PURPOSE

This study aimed to study the difference in test results of online visual acuity (VA) test under different devices and screen brightness conditions and to compare online VA test with Early Treatment Diabetic Retinopathy Study (ETDRS).

METHODS

Healthy volunteers with the best corrected VA of 0.0 LogMAR or higher were recruited. VAs under ETDRS were tested first, and then online VA test (the Stanford Acuity Test, StAT) visual acuities using iPad Air2 and Microsoft Surface pro4 under 50% and 100% screen brightness were performed. The VA results and the testing times were compared between different devices and screen brightness conditions.

RESULTS

A total of 101 eyes were included in this study. The VA results measured by the StAT were better than those of ETDRS. The VA results measured at 100% screen brightness were better than those of 50% brightness (mean difference, 0.013 logMAR at most, less than 1 letter); the VA results measured by iPad Air2 were better than those of Surface pro4 (mean difference, -0.009 logMAR at most, less than 1 letter). Significantly less time was spent on VA testing under StAT than that under ETDRS.

CONCLUSION

The impact of screen brightness and the device on the VA results generated by online VA tests was clinically insignificant. In addition, online VA tests are found to be reliable and more time efficient than ETDRS.

Visual acuity time in range: a novel concept to describe consistency in treatment response in diabetic macular oedema

OBJECTIVE

To assess 'time in range' as a novel measure of treatment response in diabetic macular oedema (DMO).

METHODS

This post hoc analysis of the Protocol T randomised clinical trial included 660 individuals with centre-involved DMO and best-corrected visual acuity (BCVA) letter score ≤78-≥24 (approximate Snellen equivalent 20/32-20/320). Study participants received intravitreal aflibercept 2.0 mg, repackaged (compounded) bevacizumab 1.25 mg, or ranibizumab 0.3 mg given up to every 4 weeks using defined retreatment criteria. Mean time in range was calculated using a BCVA letter score threshold of ≥69 (20/40 or better; minimum driving requirement in many regions), with sensitivity analyses using BCVA thresholds from 100 to 0 (20/10 to 20/800) in 1-letter increments.

RESULTS

Time in range was defined as either the absolute or relative duration above a predefined BCVA threshold, measured in weeks or as a percentage of time, respectively. Using a BCVA letter score threshold of ≥69 (20/40 or better), the least squares mean time in range (adjusted for baseline BCVA) in Year 1 was 41.2 weeks with intravitreal aflibercept, 4.0 weeks longer (95% CI: 1.7, 6.3; p = 0.002) than bevacizumab and 3.6 weeks longer (1.3, 5.9; p = 0.004) than ranibizumab. Overall, mean time in range was numerically longer for intravitreal aflibercept for all BCVA letter score thresholds between 92 and 30 (20/20 to 20/250). In the Day 365-728 analysis, time in range was 3.9 (1.3, 6.5) and 2.4 (0.0, 4.9) weeks longer with intravitreal aflibercept vs bevacizumab and vs ranibizumab (p = 0.011 and 0.106), respectively.

CONCLUSION

BCVA time in range may represent another way to describe visual outcomes and potential impact on vision-related functions over time for patients with DMO and provide a better understanding, for physicians and patients, of the consistency of treatment efficacy.

Diagnostic Accuracy of Online Visual Acuity Testing of Paediatric Patients

Background/Objectives

Remote assessment of children's visual acuity became necessary during the COVID-19 pandemic. This study aimed to assess the extent of agreement between hospital-based clinical testing and clinician-led home-based testing.

Subjects/Methods

50 children aged 2-16 (median 8) years attending hospital eye services at two UK hospitals had routine hospital-based acuities compared with subsequent online, orthoptist-supervised home visual acuities. Agreement was assessed using intra-class correlation and Bland-Altman plots, as was test-retest (TRT) agreement of two, repeated home acuity tests.

Results

Monocular acuities tested at hospital and at home were obtained from all 50 children; 33 also had binocular acuities in both settings and 35 had acuities retested immediately at home. Most children were tested at home using a computer or tablet; two were tested with a smartphone. No mean test differences were found for hospital vs home testing (-0.004 (95% CI -0.06-0.05) and -0.008 (95% CI -0.04-0.03) for binocular and monocular testing, respectively). Limits of agreement (LOAs) were ±0.32 and ±0.35 logMAR for binocular and monocular testing, respectively. LOAs for inter-ocular acuity differences (hospital vs home) were -0.15-0.25 logMAR. TRT monocular acuity agreement was excellent, with an LOA of ±0.14 logMAR.

Conclusions

We found good (binocular) and excellent (monocular) agreement between hospital and home acuity testing. LOAs were in keeping with multiple changes between measures (test; setting; time; tester) and a cohort including patients as young as two years old. Even smartphone testing proved feasible. Inability of the supervising orthoptist to check test distance or device calibration/orientation was a limitation, likely contributing to the breadth of LOAs. Home vision testing is feasible and accurate, but its precision, acceptability, health economic impact and carbon impact require more attention.

Web-based visual acuity testing for children

PURPOSE

To evaluate a newly developed, web-based system for at-home pediatric visual acuity testing and to compare results with standard in-office visual acuity test results.

METHODS

Children aged 3-12 years with and without visual deficits were enrolled (N = 65; 130 eyes). Monocular visual acuity was tested in-office using the ATS-HOTV (ages 3-6) or E-ETDRS (ages 7-12) protocol. Each child's family was emailed a link to a web-based version of the same visual acuity test for at-home testing. Equivalence was evaluated by using a linear mixed model to estimate the mean difference between in-office and at-home visual acuity test results and the corresponding two-sided 95% confidence interval.

RESULTS

For children tested with the ATS-HOTV protocol, the mean difference between in-office and at-home visual acuity test results was 0.01 log MAR (95% CI, -0.06 to 0.09). For children tested with the E-ETDRS protocol, the mean difference was 0.04 log MAR (95% CI, -0.06 to 0.14).

CONCLUSIONS

At-home, web-based ATS-HOTV and E-ETDRS visual acuity test results had excellent concordance with in-office visual acuity testing. If the burden of travel is significant, at-home testing of children's visual acuity may provide the information needed to continue care when it might otherwise be discontinued or delayed.

Validation of Home Visual Acuity Tests for Telehealth in the COVID-19 Era

Importance

Visual acuity (VA) is one of the most important clinical data points in ophthalmology. However, few options for validated at-home VA assessments are currently available.

Objective

To validate 3 at-home visual acuity tests in comparison with in-office visual acuity.

Design, Setting, and Participants

Between July 2020 and April 2021, eligible participants with VA of 20/200 or better were recruited from 4 university-based ophthalmology clinics (comprehensive, cornea, glaucoma, and retina clinics). Participants were prospectively randomized to self-administer 2 of 3 at-home VA tests (printed chart, mobile phone app, and website) within 3 days before their standard-of-care clinic visit. Participants completed a survey assessing usability of the at-home tests. At the clinic visit, best-corrected Snellen distance acuity was measured as the reference standard.

Main Outcomes and Measures

The at-home VA test results were compared with the in-office VA test results using paired and unpaired t tests, Pearson correlation coefficients, analysis of variance, χ2 tests, and Cohen κ agreement. The sensitivity, specificity, positive predictive value, and negative predictive value of each at-home test were calculated to detect significant VA changes (≥0.2 logMAR) from the in-office baseline.

Results

A total of 121 participants with a mean (SD) age of 63.8 (13.0) years completed the study. The mean in-office VA was 0.11 logMAR (Snellen equivalent 20/25) with similar numbers of participants from the 4 clinics. Mean difference (logMAR) between the at-home test and in-office acuity was -0.07 (95% CI, -0.10 to -0.04) for the printed chart, -0.12 (95% CI, -0.15 to -0.09) for the mobile phone app, and -0.13 (95% CI, -0.16 to -0.10) for the website test. The Pearson correlation coefficient for the printed chart was 0.72 (95% CI, 0.62-0.79), mobile phone app was 0.58 (95% CI, 0.46-0.69), and website test was 0.64 (95% CI, 0.53-0.73).

Conclusions and Relevance

The 3 at-home VA test results (printed chart, mobile phone app, and website) appeared comparable within 1 line to in-office VA measurements. Older participants were more likely to have limited access to digital tools. Further development and validation of at-home VA testing modalities is needed with the expansion of teleophthalmology care.