Does my child have to be able to read before I take them to the optician?
No. Opticians have tests that can be used with infants and preschool children who cannot read. If you have any concerns about your child's vision you should find a local optician who will test their vision, even if they are very young.
If you've got no urgent concerns, it might be better to wait until your child is a little older - say around three and a half years old - before taking them for their first full eye examination.
Even if your child's vision seems good, it's worth taking them for a full sight test when they reach school age, just to make sure there aren't any issues with their vision that could affect their early school years.