A much cheaper test to try is the D15, where you just arrange little black pot things with the colour in the middle in a certain order that make up a spectrum. D15 have 15 pots, D30 has 30, and so on. Much more accurate than an ishyhura, which I failed (and passed the D15!). But, whatever you do while taking the sets, USE THE TIME ALLOWED! Do NOT rush it, and look over the dots two or three times before you are sure! For Irish PPRu Ners, there's a guy in Galway who does it, he's v. good! Highest recommendations! He did his best for me and my eye problems. His offices are above the jewellers straight across the street from the Corbetts Court entrance to Eyre Square shopping centre! forget the name, but trust me, ask for the D15