K.H.
I took my almost 4 yo (at the time) to my local pearle vision and he didn't need to know his letters. They checked his vision and for color blindness and this year did the air puff glaucoma test and took a picture of his eye to check his optic nerve, blood vessels, and macula. Dilation was an option but I opted to pay more and get the photo instead. I would just call first and see what services are offered.
As to the value of a chain doctor, the opthamologist at the chain I go to diagnosed my thyroid issue before my general practitioner. Sometimes these things just work out.