Evaluation of Letters Versus Numbers (ELEVEN) Study

Study Overview
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Brief Summary
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This is a prospective randomised controlled trial to determine the performance of Best Corrected Visual Acuity (BCVA) scores using the ETDRS number chart were compared with ETDRS alphabet chart in healthy eyes of patients who do not recognise the English alphabet.

Detailed Description
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BACKGROUND: The measurement of visual acuity is important in the clinical setting to assess visual function and treatment response, while in research to provide objective clinical outcomes. The current gold standard for visual acuity measurement in most research studies, including major clinical trials, is the Early Treatment Diabetic Retinopathy Study (ETDRS) chart designed by Bailey and Lovie. However, this may not be suitable for participants who are illiterate. Alternatives exist, including the ETDRS numbers chart, Landolt C chart and Tumbling E chart. Existing studies show that the Landolt C and Tumbling E charts are alternatives with agreement with ETDRS letters chart in healthy and diseased eyes. However, the charts are limited by their 25% (if four orientations) or 12.5% (if eight orientations) chance of guessing the orientation of the letter. The ETDRS numbers chart may overcome this limitation, as it uses five unique numbers instead of a single rotating letter. There are few studies evaluating the different types of visual acuity measurement among those unfamiliar with the English alphabet. Though one study shows high repeatability and agreement between the ETDRS letters and numbers charts in healthy and diseased eyes of English literate individuals and shorter testing duration when using the numbers chart, this finding has not been validated in individuals unfamiliar with the English alphabet. This study aims to evaluate how the ETDRS letters and numbers charts compare in individuals unfamiliar with the English alphabet. METHODS: Eligible subjects were divided into 2 groups according to level of literacy. Literacy was determined by self-reported exposure to the English alphabet and recognition of the 10 Sloan letters (C, D, H, K, N, O, R, S, V, and Z). Subjects included were classified into the 2 groups: group A, with no exposure to the English alphabet and recognition of <6/10 letters, and group B, with exposure to the English alphabet and recognition of ≥6/10 letters. Testing: Each subject underwent 2 rounds of BCVA measurements using 2 types of ETDRS charts in randomized sequence as follows: LN or NL (L = ETDRS letters chart, N = ETDRS numbers chart) from Precision Vision® (PV). The randomization of the testing sequence was performed by a study coordinator independent of study recruiter, optometrist or investigator. Sequentially numbered, opaque and sealed envelopes were used for allocation concealment and opened by the optometrist prior to testing. The tests were performed and recorded by a single optometrist in the same testing room with similar lighting conditions. For every round of testing, the right eye was examined first, followed by the left eye. For the right eye, numbers chart (PV No. 2702A) and letters chart (PV No. 2173) were used. For the left eye, the numbers chart (PV No. 2714A) and letters chart (PV No. 2174) were used. Different charts (with the same optotypes but in different order) were used for right and left eyes to minimize the effect of learning between consecutive tests.

Official Title
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Evaluation of Letters Versus Numbers (ELEVEN) Study: ETDRS Visual Acuity Chart Performance in an English Alphabet Illiterate Population

Conditions
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Visual Acuity

Intervention / Treatment
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* Diagnostic Test: Visual acuity assessment by ETDRS charts


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Hong Kong residents Age 50 years or above Attending Southern District Screening program Exclusion Criteria: BCVA 20/200 or below Any clinically relevant ocular disease that might affect visual acuity

Ages Eligible for Study
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Minimum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Prospective randomized controlled trial
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: English alphabet illiterate group<br>Individuals with no self-reported understanding of English alphabet and recognition of <6/10 Sloan Letters | Diagnostic Test: Visual acuity assessment by ETDRS charts<br>* All participants must complete VA measurement of both eyes using 2 charts including the ETDRS letters chart and ETDRS numbers chart.<br>|
| Active Comparator: English alphabet literate group<br>Individuals with self-reported understanding of English alphabet and recognition of ≥6/10 Sloan Letters | Diagnostic Test: Visual acuity assessment by ETDRS charts<br>* All participants must complete VA measurement of both eyes using 2 charts including the ETDRS letters chart and ETDRS numbers chart.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| BCVA Measurements | Assessment of BCVA using ETDRS numbers and letters chart and its comparison between the testing groups and intervention methods. All visual acuity tests were performed at 3 metres with at least 15 seconds between each chart. Subjects were asked to read as many optotypes as possible according to the ICO Visual Acuity Measurement Standard. | 1 day | 
| Testing Duration | Assessment of testing duration using ETDRS numbers and letters and its comparison between the testing groups and intervention methods. The testing durations of each visual acuity test were measured and recorded by a single timekeeper with a standard digital chronometer. | 1 day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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ETDRS visual acuity, English alphabet illiterate, ETDRS number chart