Optometrists are at the forefront of identifying eye disease: around 40–50% of referrals to ophthalmology departments originate from optometrists (Harrison et al. 1988, Jones et al. 1990, Pooley & Frost 1999). Around 96% of referrals for suspected glaucoma originate from optometrists (Bell & O’Brien 1997), and a recent study found that, of a group of patients in the USA with glaucoma or suspected of having glaucoma, more than half were diagnosed at a routine eye examination with no ocular symptoms (Quigley & Jampel 2003). The College of Optometrists’ Guidelines for Professional Conduct state that for all patients judged to be at risk of glaucoma it is good practice to perform all three diagnostic tests, namely examination of the optic disc, tonometry and central visual field examination (College of Optometrists 1997, updated 2000). Patients judged to be at risk of glaucoma include all patients over the age of 40 and so it is considered good practice to perform visual field tests on everyone over 40.