Philip Walsh - Why Do Pupils Dilate?

Publish Date
Friday, 10 June 2016, 12:05PM
By Philip Walsh

Ever noticed how pupils grow and shrink in different lights, or when you enter a different room?

The pupil’s job is to allow light to penetrate the eyes. The black circles in your eyes shrink and grow due to the iris expanding or shrinking to let more or less light into the eyes.

When you’re in a well-lit room, you will find that pupils are very small because there is a sufficient amount of light reaching the eye. The same goes when you step into a dark room, your pupils will dilate to allow more light into the eye to ensure a clear image.

If you find you have constantly dilated or enlarged pupils, it is important to visit your local optometrist for an eye exam. Being exposed to bright conditions with fully dilated pupils can overwhelm the eyes and cause damage if not treated.

For more information or if you have concerns about your eye health, talk to your local Specsavers optometrist or visit

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