Reading an eye chart, most commonly the Snellen chart, is a straightforward way to measure your visual acuity, which is how clearly you can see.
The process involves standing a specific distance away and identifying letters on lines that decrease in size. This helps determine if you have 20/20 vision or if your vision is better or worse than average.
What is a Snellen Chart?
A Snellen chart typically displays rows of letters that get progressively smaller from top to bottom. The largest letter is usually at the very top. Each row is assigned a number representing a specific visual acuity.
Step-by-Step Guide to Reading the Chart
To properly read a Snellen chart for a standard vision test, follow these steps:
- Position Yourself: Stand 20 feet away from the chart. This is the standard distance for the Snellen test.
- Cover One Eye: Use your hand or an occluder (like a small paddle) to cover one eye. Ensure the eye is fully covered but not pressed shut, as this can temporarily affect vision.
- Read the Chart: With your uncovered eye, begin reading the rows of letters. Start with the largest letters starting at the top and continue working your way to the bottom. Read the letters out loud as clearly as possible.
- Identify the Smallest Line: Continue reading down the chart until you reach a line where you can no longer clearly distinguish the letters. Note which line you successfully read.
- Switch Eyes: When you finish with one eye, restart the test with your other eye uncovered. Repeat the process from step 2, this time covering the eye you just tested.
Your visual acuity for each eye is determined by the smallest line of letters you could accurately read. For example, reading the line marked '20/20' means you can see at 20 feet what a person with average vision sees at 20 feet. If you can only read the '20/40' line, it means you see at 20 feet what an average person could see clearly at 40 feet.
This process is a fundamental part of a comprehensive eye examination performed by eye care professionals.
