Description

The ETDRS Chart, or Early Treatment Diabetic Retinopathy Study Chart, is a highly specialized tool designed for the precise measurement of visual acuity. It is widely recognized and utilized in clinical trials, research settings, and ophthalmic practices due to its standardized design and reliable performance.

Key Features

• Sloan Letters: Each line of the chart comprises five Sloan letters, carefully chosen to maintain consistent difficulty. These letters are arranged to prevent the formation of words or acronyms, ensuring unbiased testing.

• LogMAR Progression: The chart features a geometric progression in letter size and spacing, known as LogMAR, which provides proportional spacing between lines. This design enhances the accuracy and consistency of visual acuity assessments.

• Multiple Variants: The ETDRS Chart is available in several versions, including Chart R for refraction, Chart 1 for the right eye, and Chart 2 for the left eye. It comes in both the Original Series and 2000 Series, with options for low-contrast versions.

Material and Construction

• Durable Materials: Constructed from non-reflective white polystyrene or styrene plastic, the chart is printed with high-contrast optotypes. It is UV-coated, allowing for easy cleaning with mild soap and water.

• Format Options: Available in roll-up and rigid formats, the chart offers flexibility in portability and durability to suit various clinical needs.

Dimensions

• Size: The chart measures approximately 64.8 cm by 62.2 cm, with slight variations within standard manufacturing tolerances.

Illumination

• Lighting Requirements: Designed for use with a calibrated illuminator cabinet, the chart requires uniform lighting with a recommended luminance of 85 cd/m². It is compatible with ESV3000™ and ESC2000™ illuminated cabinets.

• Light Source: The standard light box uses 40-watt frosted cool white fluorescent bulbs, which should be replaced annually to maintain optimal performance.

Testing Protocol

• Distance: Standard testing is conducted at a distance of 4 meters, with protocols in place for reduced vision assessments at 1 meter.

• Scoring: Visual acuity is scored by counting correctly identified letters, with LogMAR calculations providing detailed quantitative data.

Clinical Use

• Gold Standard: The ETDRS Chart is considered the gold standard for visual acuity measurement, extensively validated by scientific literature and used in studies by the National Eye Institute.

• Age Suitability: It is suitable for individuals aged 5 years and older, offering published population age-norms for comprehensive analysis.

Maintenance

• Cleaning: The chart can be cleaned with mild soap and water, while the light box bulbs require annual replacement. Room illumination should be maintained between 50 and 100 foot-candles for optimal testing conditions.

The ETDRS Chart's rigorous standardization and robust construction make it an invaluable asset for accurate and reproducible vision testing across diverse clinical and research environments.