Visual acuity facts for kids

Visual acuity (VA) is how clearly you can see things, especially shapes and details. It depends on how well your eye can focus light onto the retina (the back part of your eye), how sensitive your nerves are, and how well your brain understands what you're seeing.

VA is a way to measure how small a black symbol you can identify on a white background from a set distance. It tells us the smallest size you can reliably see. It's the most common test doctors use to check your vision.

Some people might have other vision problems, like color blindness (trouble seeing certain colors) or difficulty seeing things with low contrast (like light gray on dark gray). They might also struggle to track fast-moving objects, but still have normal visual acuity. So, having normal visual acuity doesn't always mean your vision is perfect. However, visual acuity is widely used because it's a good way to see how well someone can do everyday activities.

What is Visual Acuity?

Visual acuity measures the sharpness of your vision. It tells doctors how clearly you can see details. Imagine reading a sign from far away; your visual acuity helps you see the letters clearly. It's a very important part of how we see the world around us.

How Your Eye Sees

Your eye works a bit like a camera. Light enters through the front, passes through the lens, and focuses on the retina at the back. The retina has special cells that turn light into electrical signals. These signals then travel to your brain, which interprets them as images. Good visual acuity means this whole process works well.

Why Visual Acuity Matters

Having good visual acuity is important for many daily tasks. It helps you read books, see the blackboard at school, drive a bike, or recognize faces from a distance. If your visual acuity isn't good, it can make these activities harder.

Measuring Visual Acuity

Doctors use special charts to measure visual acuity. The most common one is the Snellen chart. This chart has rows of letters that get smaller as you go down.

The Snellen Chart

When you get your eyes checked, you usually stand a certain distance from a Snellen chart. The eye doctor will ask you to read the smallest line of letters you can see. Your visual acuity is then written as a fraction, like 20/20 or 6/6.

What Do the Numbers Mean?

• 20/20 vision (or 6/6 in meters) means you can see at 20 feet what a person with normal vision can see at 20 feet. It's considered normal, clear vision.
• 20/40 vision means you have to be 20 feet away to see what a person with normal vision can see from 40 feet away. This means your vision is not as sharp.
• The top number (20) is the distance you are from the chart in feet.
• The bottom number is the distance at which a person with normal vision can read the same line.

Other Vision Tests

While visual acuity is important, it's not the only part of good vision. Doctors also check for:

• Color vision: Your ability to see different colors.
• Contrast sensitivity: How well you can see objects that don't stand out much from their background.
• Peripheral vision: What you can see out of the corners of your eyes without moving your head.
• Eye movement: How well your eyes work together and track moving objects.

So, even if your visual acuity is normal, your eye doctor might still find other vision issues. This is why a full eye exam is so important!

Images for kids

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  Eye examination for visual acuity

See also

In Spanish: Agudeza visual para niños