Comparison of Snellen Visual Acuity Measurements in Retinal Clinical Practice to Electronic ETDRS Protocol Visual Acuity Assessment

Magnitude of Visual Acuity Change with ETDRS versus Snellen Testing in Clinical Trials: Implications for Clinic-Based Outcomes

Purpose

To compare visual acuity (VA) changes using standardized ETDRS best-corrected visual acuity (BCVA) and nonstandardized Snellen VA among subjects enrolled in clinical trials.

Design

Retrospective study.

Participants

Patients enrolled in prospective clinical trials at 3 urban retina practices.

Methods

Best available Snellen VA at the clinic visit before study entry and after exit were compared with the ETDRS BCVA at trial entry and exit. The correlation and discrepancies between Snellen VA and ETDRS methods as well as the VA changes from trial entry to exit were evaluated.

Main Outcome Measures

The discrepancy between VA change from trial entry to exit using Snellen VA versus ETDRS BCVA methods.

Results

A total of 273 eyes were included. The mean (standard deviation [SD]) Snellen VA was 58.1 (20) ETDRS-equivalent letters (Snellen 20/69) at the clinic visit before trial entry and 61.6 (21) ETDRS-equivalent letters (Snellen 20/59) at the visit after trial exit. The mean (SD) ETDRS BCVA was 65.5 (16) letters (Snellen 20/49) at trial entry and 70.5 (17) letters (Snellen 20/39) at trial exit. The mean VA change from trial entry to exit was not significantly different for ETDRS (5 letters of vision gain) compared with Snellen (3.6 letters of vision gain) methods (P = 0.061). Eyes with baseline Snellen VA 20/50 or worse gained significantly more letters using Snellen (9.3 ± 22.3 letters) compared with ETDRS (5.2 ± 18.7 letters; P = 0.012). Among eyes with baseline Snellen VA of > 20/50, VA gain was significantly greater with the ETDRS method (4.9 ± 12.3 letters) compared with Snellen (-1.5 ± 12.3 letters; P < 0.001).

Conclusions

The mean VA change from clinical trial entry to exit was similar between the ETDRS and Snellen methods. However, among patients with worse baseline Snellen vision, the magnitude of VA change was greater with Snellen compared with ETDRS, whereas among those with better baseline vision, this magnitude was greater with the ETDRS method. Understanding the proportion of the study population with varying VA levels may have implications for interpreting VA outcomes from retrospective clinic-based studies compared with those reported in clinical trials.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Inter-Rater Reliability of EyeSpy Mobile for Pediatric Visual Acuity Assessments by Parent Volunteers

Purpose

To assess the inter-rater test reliability of the EyeSpy Mobile visual acuity smartphone algorithm when administered to children by eye professionals and parent volunteers.

Patients and Methods

Visual acuity test-retest results were analyzed for 106 children assigned to one of three different screenings: (1) An eye technician and pediatric ophthalmologist using their typical visual acuity testing method on a M&S computer; (2) An eye technician and pediatric ophthalmologist using EyeSpy Mobile; (3) An eye technician and parent volunteer using EyeSpy Mobile.

Results

All three phases demonstrated a strong agreement between the two testers, with mean test-retest equivalency results within 0.05 logMAR (2.5 letters, 90% CI). Whether testing using their typical technique on an M&S computer or using EyeSpy Mobile, eye professionals obtained statistically closer mean test-retest results than parent volunteers by 1 letter, with equivalency results within 0.03 logMAR (1.5 letters, 90% CI). Conversely, the number of retests within 2 vision lines was statistically greater when EyeSpy mobile was used by parents as compared to eye professional's customary technique on the M&S computer.

Conclusion

EyeSpy Mobile provides clinically useful visual acuity test-retest results even when used by first-time parent volunteers. Adaptive visual acuity algorithms have the potential to improve reliability, lessen training requirements, and expand the number of vision screening volunteers in community settings.

Visual Acuity Examination Methodology in Keratoconus

Visual acuity is one of the most important parameters for evaluating the vision of patients with keratoconus. This study reviewed 295 articles related to keratoconus published between 2017 and 2022 in which visual acuity was one of the parameters measured. The methodology of visual acuity testing in studies on keratoconus was thoroughly analyzed. The analysis showed that the most commonly indicated chart for testing visual acuity papers on keratoconus is the Snellen chart. It was shown that in 150 out of 295 articles, the authors do not describe the methodology for testing visual acuity. What is more, it was also shown that in 68 of the 295 articles which were analyzed, a procedure for converting visual acuity tested with a Snellen chart into a logMAR scale was used. In this review, we discuss the validity and reliability of such conversions. In particular, we show that insufficient description of visual acuity testing methodology and lack of information on the conversion of visual acuity results into the logMAR scale may contribute to the misinterpretation of visual acuity test results.

Accuracy of Artificial Intelligence in Estimating Best-Corrected Visual Acuity From Fundus Photographs in Eyes With Diabetic Macular Edema

Importance

Best-corrected visual acuity (BCVA) is a measure used to manage diabetic macular edema (DME), sometimes suggesting development of DME or consideration of initiating, repeating, withholding, or resuming treatment with anti-vascular endothelial growth factor. Using artificial intelligence (AI) to estimate BCVA from fundus images could help clinicians manage DME by reducing the personnel needed for refraction, the time presently required for assessing BCVA, or even the number of office visits if imaged remotely.

Objective

To evaluate the potential application of AI techniques for estimating BCVA from fundus photographs with and without ancillary information.

Design, Setting, and Participants

Deidentified color fundus images taken after dilation were used post hoc to train AI systems to perform regression from image to BCVA and to evaluate resultant estimation errors. Participants were patients enrolled in the VISTA randomized clinical trial through 148 weeks wherein the study eye was treated with aflibercept or laser. The data from study participants included macular images, clinical information, and BCVA scores by trained examiners following protocol refraction and VA measurement on Early Treatment Diabetic Retinopathy Study (ETDRS) charts.

Main Outcomes

Primary outcome was regression evaluated by mean absolute error (MAE); the secondary outcome included percentage of predictions within 10 letters, computed over the entire cohort as well as over subsets categorized by baseline BCVA, determined from baseline through the 148-week visit.

Results

Analysis included 7185 macular color fundus images of the study and fellow eyes from 459 participants. Overall, the mean (SD) age was 62.2 (9.8) years, and 250 (54.5%) were male. The baseline BCVA score for the study eyes ranged from 73 to 24 letters (approximate Snellen equivalent 20/40 to 20/320). Using ResNet50 architecture, the MAE for the testing set (n = 641 images) was 9.66 (95% CI, 9.05-10.28); 33% of the values (95% CI, 30%-37%) were within 0 to 5 letters and 28% (95% CI, 25%-32%) within 6 to 10 letters. For BCVA of 100 letters or less but more than 80 letters (20/10 to 20/25, n = 161) and 80 letters or less but more than 55 letters (20/32 to 20/80, n = 309), the MAE was 8.84 letters (95% CI, 7.88-9.81) and 7.91 letters (95% CI, 7.28-8.53), respectively.

Conclusions and Relevance

This investigation suggests AI can estimate BCVA directly from fundus photographs in patients with DME, without refraction or subjective visual acuity measurements, often within 1 to 2 lines on an ETDRS chart, supporting this AI concept if additional improvements in estimates can be achieved.

Visual and Anatomical Outcomes of a Single Intravitreal Dexamethasone in Diabetic Macular Edema: An 8 Year Real-World Study

IMPORTANCE

Diabetic macular edema (DME) is a major cause of vision loss in patients with diabetes mellitus. Intravitreal dexamethasone is a treatment option for patients unsuitable for or non-responsive to anti-angiogenic agents.

OBJECTIVE

To quantify visual and anatomical outcomes from an initial intravitreal dexamethasone injection over the expected 6-month period of dexamethasone release by the implant. Design and enrolment: This is a retrospective cohort study using electronic medical records of patients reviewed between 1 January 2012 and 1 April 2022.

SETTING

A tertiary eye-care center in London, United Kingdom; Moorfields Eye Hospital National Healthcare System Foundation Trust.

PARTICIPANTS

The cohort comprised 418 adult patients with DME who received an initial treatment of 700 µg intravitreal dexamethasone in the study period. Of these, 240 patients met the inclusion criteria of ≥2 hospital visits following initial injection (≥1 beyond 6 months) and no previous ocular corticosteroid treatment or missing assessment at baseline.

EXPOSURE(S)

Intravitreal dexamethasone implant (700 µg).

MAIN OUTCOME(S) AND MEASURE(S)

Probability of a positive visual outcome, defined as ≥5 or ≥10 Early Treatment Diabetic Retinopathy Study (ETDRS)-letter gain after treatment when compared to baseline (Kaplan-Meier models).

RESULTS

From the initial intravitreal dexamethasone injection alone, we observed a >75% chance of gaining ≥5 ETDRS letters and >50% chance of gaining ≥10 ETDRS letters within 6 months. There was less than a 50% chance of sustaining either positive visual outcome beyond 4 months.

CONCLUSIONS AND RELEVANCE

Most patients can be expected to have a positive visual outcome following an initial injection of dexamethasone implants that subsides within 4 months. Real-world re-treatment was observed to be delayed until after visual benefits were lost in half of the cohort. Further research will be needed to study the effects of delays in re-treatment.

Relevance of Visual Acuity Measurement for Therapeutic Decisions in Diabetic Macular Edema

This study aimed to determine the validity of basing retreatment decisions on anatomical criteria alone (captured using optical coherence tomography (OCT)-OCT-guided strategy) rather than the gold standard (combined visual acuity (VA) and OCT) in patients with diabetic macular edema (DME). This cross-sectional study included 81 eyes undergoing treatment for DME from September 2021 to December 2021. An initial therapeutic treatment decision based on OCT results was made on inclusion. Subsequently, in light of the patient's VA score, this initial decision was upheld or adjusted, and the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. In 67 out of the 81 eyes included in the study (82.7%), the OCT-guided strategy produced equivalent results to the gold standard. In this study, the OCT-guided retreatment decision strategy yielded sensitivity and specificity of 92.3% and 73.8%, respectively, and PPV and NPV of 76.6% and 91.2%, respectively. These findings differed according to the patient's treatment regimen: the sensitivity and specificity for eyes under a treat and extend regimen was higher, 100% and 88.9%, respectively, than eyes under a Pro Re Nata regimen, 90% and 69.7%, respectively. These findings show that VA testing could be omitted from the follow-up of certain patients with DME treated with intravitreal injections without impacting the quality of care.