Description

The ETDRS Chart, or Early Treatment Diabetic Retinopathy Study Chart, is a highly specialized tool designed for precise visual acuity measurement. Widely used in clinical and research settings, it serves as a gold standard for ophthalmology trials and low vision assessments.

Key Features

• Sloan Letters: Each line of the chart features five Sloan letters, chosen for their consistent recognition difficulty. The arrangement avoids forming words or acronyms, ensuring unbiased results.
• LogMAR Progression: The chart employs a geometric progression in letter size and spacing, known as LogMAR, to provide accurate and reproducible measurements.
• Multiple Versions: Various versions of the chart are available to prevent memorization, enhancing the reliability of repeated tests.

Design and Materials

• Dimensions: The chart typically measures around 64.8 cm x 62.2 cm, crafted from non-reflective, white polystyrene.
• Illumination: Designed for use with a calibrated illuminator cabinet, it ensures standardized lighting conditions with luminance levels between 85–160 cd/m².
• Compatibility: Suitable for both traditional and LED illuminator cabinets, providing flexibility in diverse clinical environments.

Testing Protocols

• Distance: Standard testing distances are 4 meters and 1 meter for those with low vision.
• Scoring: Utilizes letter-by-letter scoring or LogMAR scoring, with results expressed in various notations.
• Age Suitability: Appropriate for individuals aged 5 years and older, with specific protocols for each eye.

Clinical Application

Recognized globally, the ETDRS Chart is essential for best-corrected visual acuity measurement in clinical trials, particularly in studies related to diabetic retinopathy. Its use is often mandated by regulatory bodies like the US FDA, ensuring consistent data collection across multiple sites.

Maintenance

The chart can be easily cleaned with mild soap and water, while illuminator bulbs should be replaced annually. Proper room illumination should be maintained for optimal performance.

Integration and Accessories

Available in both physical and digital formats, the chart can be integrated into computerized vision testing systems. Accessories such as chart storage and mobile bases enhance its usability in various settings.

Special Considerations

As a recognition acuity test, the ETDRS Chart is distinct from refraction charts and may require specific protocols and examiner certification in clinical trials. It is frequently referenced in protocols from the National Eye Institute, underscoring its pivotal role in ocular function studies.