Advise on my child's learning

If possible could
You please post this question? Thanks

My son turns 5 this month and had started prep. He attended daycare with a kindy program 4 days
Per week since he
Was 18 mths. His prep teacher said he isn't dong to well with learning. He can write his name and name squares, circles and rectangles. However he only recognises 3 letters of the alphabet (she said he should know 18 by now and his name has 5 ) and doesn't recognise any number(he can count to twenty but she said he should recognise at least 15 numbers). The teacher recommended we take him to a behavioural optometrist. I have taken him but am a little confused. The op said he needed to see a chiropractor because of his retained neonatal reflexes (specifically his Palmer reflex). He also wants him to see a vision specialist to help him learn to see better?? He also said his vision is perfect but to get him glasses to wear when reading and writing to help his focus? He then told me I may need to consider keeping him back in prep next year. He also said to teach him by play based learning (which makes sense). His teacher said He is a very happy well behaved little boy but he isn't really picking anything up. Has anyone ever had this before or could offer some advise? TIA