To be honest that prescription should be sufficient as it will show how many dioptres your eyes are - in order to get a class 1 medical you need to be within + or - 3.00 dioptres. Unfortunatley that doesn't show whether you're colour blind so the best thing to take down, if i was going would be my class 1 medical certificate-however, i understand that some people dont have these so can only assume that the next best alternative is a prescription from the optician.