Understanding

your prescription

Interpreting your glasses prescription can be completely baffling. Understanding how the numbers on it relate to our day-to-day vision can be hard too. There’s sometimes understandable anxiety about it, but there needn’t be. Read on to learn more about:

  1. The most common vision issues and their causes.
  2. How different lens shapes help by bending light.
  3. What the numbers on your prescription actually mean.

Common vision problems

Most prescriptions will describe the extra refraction needed to correctly focus light on your retina, depending on your specific needs. (Refraction is just a fancy word for bending light.)

Different eye conditions require different lens shapes to bend light in the right way. Your prescription is the key to choosing and using the right lens.

There are three highly common vision problems: myopia, hypermetropia and astigmatism. The diagram describes how they relate to a normal eye.

Myopia (short-sightedness): light is focused in front of your retina, possibly due to a strong lens or an elongated eyeball, making it hard to focus on things far away.

Hypermetropia (far-sightedness): light is focused behind your retina, possibly due to a weak lens or a shortened eyeball, making it hard to focus on things up close.

Astigmatism: this can accompany both myopia and hypermetropia, and is also quite common. Light is focused on several points on your retina, making hard edges visually fuzzy.

For extra cred, here’s one more…

Presbyopia: this is typically an age-related problem, occurring in people aged 45 and up, due to stiffening of the eye’s lens. Light is not focused at any point on the retina, making it hard to focus on things both near and far.

You’re one step closer to interpreting your prescription!

Glass prism. Image: Han Cheng Yeh / Flickr