---
title: Repeatability and Concordance of VA Measured With ETDRS Numeric , Landolt C, and Letter Charts in Thai Individuals
nct_id: NCT02810665
overall_status: UNKNOWN
sponsor: Chiang Mai University
study_type: OBSERVATIONAL
primary_condition: Visual Nonspecific
countries: Thailand
canonical_url: "https://parkinsonspathways.com/agent/trials/NCT02810665.md"
clinicaltrials_gov: "https://clinicaltrials.gov/study/NCT02810665"
ct_last_update_post_date: 2016-06-23
last_seen_at: "2026-05-12T07:17:57.385Z"
source: ClinicalTrials.gov (mirrored, no enrichment)
---
# Repeatability and Concordance of VA Measured With ETDRS Numeric , Landolt C, and Letter Charts in Thai Individuals

**Official Title:** Repeatability and Concordance of Visual Acuity Level Measured With ETDRS Numeric Charts, ETDRS Landolt C Charts, and Original ETDRS Letter Visual Acuity Charts in Thai Individuals

**NCT ID:** [NCT02810665](https://clinicaltrials.gov/study/NCT02810665)

## Key Facts

- **Status:** UNKNOWN
- **Study Type:** OBSERVATIONAL
- **Target Enrollment:** 180
- **Lead Sponsor:** Chiang Mai University
- **Conditions:** Visual Nonspecific
- **Start Date:** 2015-07
- **Completion Date:** 2016-07
- **CT.gov Last Update:** 2016-06-23

## Brief Summary

This is a cross-sectional study to determine the repeatability and concordance of visual acuity level measured with the original ETDRS letter, ETDRS Landolt C, and ETDRS numeric chart in Thai individuals.

## Detailed Description

The ETDRS visual acuity chart has been used as a standard visual acuity measurement chart in ophthalmic clinical trials due to its proven high repeatability comparing to other visual acuity chart. However, the original ETDRS alphabet chart could not be used in every individual around the world, especially those who are non-english speakers. Landolt C chart has been a recommended chart to test visual acuity in those living in a country where English is not a common language, however, some difficulties including right-left confusion occurred when testing with the Landolt C chart, leading to the unreliable results of visual acuity measurement using the Landolt C chart. Recently, the ETDRS numeric chart was introduced by some medical equipment companies but there is limited information regarding the repeatability and concordance of the new ETDRS numeric chart comparing to the original ETDRS alphabet and Landolt C chart.

Therefore, this study aims to determine the repeatability and concordance of visual acuity level measured with the original ETDRS alphabet, the ETDRS Landolt C, and the ETDRS numeric chart. Results from this study would be able to suggest an appropriate ETDRS chart to be used in clinical studies in Thailand or other countries where English is not the native language.

## Eligibility

- **Minimum age:** 18 Years
- **Sex:** ALL
- **Healthy Volunteers:** Yes

```
Inclusion Criteria:

* Thai nationality
* More than 18 years of age
* Educational level: at least high school
* Able to read English alphabet
```

## Arms

- **Normal vision group** — Individuals with VA 20/20 to 20/25
- **Impaired vision group** — Individuals with impaired vision: VA of 20/32 to 20/200 due to either cataract, diabetic macular edema, or age-related macular degeneration

## Interventions

- **Visual acuity measurement by ETDRS chart** (BEHAVIORAL) — All participants must complete VA measurement of the study eye using 3 charts including the original ETDRS alphabet, ETDRS Landolt C, and ETDRS numeric charts for 2 times, at least 30 minutes apart.

## Primary Outcomes

- **Concordance of VA tested with ETDRS alphabet, Landolt C and numeric visual acuity charts** _(time frame: Day 1)_

## Secondary Outcomes

- **Repeatability of VA tested with ETDRS alphabet, Landolt C and numeric visual acuity charts** _(time frame: Day 1)_
- **Differences in testing duration of VA measurement across the 3 ETDRS charts** _(time frame: Day 1)_

## Locations (1)

- Voraporn Chaikitmongkol, Muang Chiang Mai, Chiang Mai, Thailand — _RECRUITING_

## Recent Field Changes (last 30 days)

- `status.overallStatus` — added _(2026-05-12)_
- `status.primaryCompletionDate` — added _(2026-05-12)_
- `status.completionDate` — added _(2026-05-12)_
- `status.lastUpdatePostDate` — added _(2026-05-12)_
- `design.enrollmentCount` — added _(2026-05-12)_
- `eligibility.criteria` — added _(2026-05-12)_
- `eligibility.minAge` — added _(2026-05-12)_
- `eligibility.sex` — added _(2026-05-12)_
- `outcomes.primary` — added _(2026-05-12)_
- `outcomes.secondary` — added _(2026-05-12)_
- `armsInterventions.arms` — added _(2026-05-12)_
- `armsInterventions.interventions` — added _(2026-05-12)_
- `sponsor.lead` — added _(2026-05-12)_
- `results.hasResults` — added _(2026-05-12)_
- `locations.voraporn chaikitmongkol|muang chiang mai|chiang mai|thailand` — added _(2026-05-12)_

---

*Canonical: https://parkinsonspathways.com/agent/trials/NCT02810665.md*  
*Source data (authoritative): https://clinicaltrials.gov/study/NCT02810665*  
*This page is a raw mirror with no AI summary, no editorial enrichment, and no Parkinson's-specific filtering.*