Your child sounds like my now 8yr old daughter. She has been wearing glasses since she has been 5 (right before kindergarten) but knew she needed glasses WAY before then. The reason why she did not wear glasses earlier was my fault and not able to find a pediatric opthamoligist..I have a great one now. Needless to say, my recommendation is to put her in glasses now. My doctor warned me her vision could change and the glasses could help improve her vision. We were on a 6 month visitation schedule and did see her vision change. One day, my daughter stated she could not see and we got her into the Dr within days of her comment and had to change her perscription. She was in kindergarten and was learning key critical concepts and I could not stand knowing she could not see.
Another benefit to her wearing the glasses now is learning responsibility and just getting used to wearing them. My daughter is great at keeping up with her glasses, partially because she does not like what she sees without glasses:)
My daughter was one of the first wearing glasses. By mid 1st grade, I want to say at least 1/3 of the class was wearing glasses!
Your daughter is 4 and is either beginning read or reading already. The glasses will help with this process so I say go for them now.
I am 47 and not wearing glasses YET..but my husband does so he is in charge of glasses purchases. We have purchased glasses from Lens Crafters and we always get the stuff that makes the glasses turn dark in the sun. My daughter loves the pink or purple tint..pay extra and get done because it is worth it.
I hope this helps. Feel free to reach out if you have questions.