Cognitive Scaffold

Preparing your thinking workspace

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MENTAL MODEL · M10153

Snellen Chart

Snellen Chart
TechnicalHigh supportMedicine
Included
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Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

Measures visual acuity using progressively smaller letters, with results expressed as a fraction (e.g., 20/20): - Numerator: testing distance - Denominator: distance at which a normal eye can read that line.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

Establish a reference standard. Quantify ability by comparison with a standard, applicable to any assessment scenario requiring a "normal value."

anchor

Anchor fast decisions

Uses rows of characters that decrease in size according to visual angle (1/5 minute of arc) to measure visual acuity, recording the distance ratio of the smallest line discernible (e.g., 20/20). It standardizes visual acuity measurement.

MINIMUM ACTION

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Source support: Explicit

  • link
    en.wikipedia.orghttps://en.wikipedia.org/wiki/Snellen_chartZH · Explicit
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