Red reflex

My son is half chinese half English. On his 6 week exam they struggled to find the red reflex in his left eye so they booked an appointment 2 weeks later and again they struggled to find it. Hes 3 months now they checked again and still struggled to find the red reflex. So I googled it and the first thing that came up was a tumour behind his eye or a cataract. But then I kept going and it said it could be that some mixed children has one paler than the other. So I am here to ask if anyone has had anything similar happen ?

We are going to the main hospital on the 27th December to let a professional look but it's the wait that's killing me