Generally, adults without any existing eye conditions should have their eyes tested every 6 years for those aged 20-39 years; every 2-3 years for those aged over 40; and every 1-2 years for those over 65. More frequent testing is typically advised for spectacle wearers and young children, with spectacle wearers requiring an annual test and children bi-annual testing. Always consult your optometrist to obtain the best advice for your needs.