My DS wears glasses to correct a squint. He's about to start school and I'm conscious that we don't have a spare pair should he break them. I thought I'd order a pair online as it's cheaper than the opticians but I don't understand the different options when filling out the prescription details.
It asks for:
SPH
CYL
AXIS
ADD
PD
I literally have (for example) Left: +2.5, Right: +2.25
Any ideas please?!