What is a Vision Chart?
A vision chart is a tool used by optometrists and ophthalmologists to measure visual acuity—how sharp or clear your vision is. The most common type is the Snellen Chart, developed in 1862 by Dutch eye doctor Herman Snellen. It features rows of letters that get progressively smaller.
For children or people who cannot read letters, other charts like E-chart (with the letter “E” pointing in different directions) and Landolt C chart (a broken ring pointing different ways) are used.
1. Snellen C Chart
2. Snellen chart [ABCD]
3. Snellen Chart [Numbers]
How Does It Work?
- You are asked to sit 20 feet (6 meters) away from the chart.
- You cover one eye at a time and read the smallest row of letters you can see clearly.
- Your results are recorded as a fraction, e.g., 20/20 vision.
👉 20/20 vision means you can see at 20 feet what a person with normal vision should see at 20 feet.
👉 20/40 vision means you need to be at 20 feet to see what a person with normal vision can see at 40 feet.
Types of Vision Charts
- Snellen Chart – Most common, with letters decreasing in size.
- LogMAR Chart – More scientific, with equal spacing between letters and rows.
- E-Chart – Designed for children or illiterate patients.
- Jaeger Chart – Used for testing near vision, usually held in the hand.
Why is the Vision Chart Important?
- Detects refractive errors like myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
- Helps in monitoring eye health over time.
- Essential for issuing driver’s licenses, school screenings, and job medicals.
- Acts as the first step in diagnosing eye problems before moving to advanced tests.
A vision chart may look like a simple board with letters, but it’s a vital diagnostic tool that gives doctors a quick snapshot of your eye health. So, the next time you’re at an eye exam and asked to “Read the smallest line you can,” remember—you’re looking through a window that reveals just how clearly you see the world.