Went for glaucoma screening, should I be worried about my results ?

Since I'm pre-diabetic, I asked the optician visiting at work to do a glaucoma screen. She said that my levels were 18 and 19 and that I should check it at every eye checkup. I spoke to a friend with glaucoma and she said those quick tests aren't accurate, and when she went for a full test her levels were actually higher. Anyone with experience?