Editor,—In his interesting article on the seven million people blind from glaucoma worldwide, Quigley highlights the need for better detection of cases with moderate and severe glaucoma damage and hence the greatest risk of blindness.1 In his editorial, Rait correctly states that the costs of standard methods of glaucoma screening, including computerised perimetry, are prohibitive in most developing countries so that glaucoma remains undiagnosed until very late in its course.2 A simple and inexpensive visual field test has been designed³specifically for the detection of moderate and severe glaucomatous visual field loss in situations precluding other methods, but Rait seems to dismiss this technique as ‘less reliable’, quoting an article⁴ that is not representative of the published literature.

The oculokinetic perimetry (OKP) glaucoma test, to which Rait referred, is a …