That is a silly explanation from that Optician who I assume is the person that makes and sells the glasses and does not do the eye testing. You are looking for an Optometrist and anyone of them should be able to do an accurate as possible eyetest on a 4yr old.

It is not just letter recognisation, it also shapes and colours and all sorts of ways to check the eyes. Not to mention having a look in the eye as well.

Most Specsavers have good Optometrists. Burke Rd has a couple of Optometrist practices which would definitely be able to do an accurate and thorough eye test on your DD. Your DD is a smart cookie, she will be fine.

Was it High Street or High Street Rd