Preschool vision screening in Cornwall: performance indicators of community orthoptists.

The performance of community orthoptists was retrospectively assessed in a primary preschool screening programme that has been established in Cornwall since 1982. The outcome of screening was compared between random samples of two birth year cohorts corresponding to the second and fourth years of existence of the screening programme (1980, n = 298 and 1982, n = 300). The mean age at screening was significantly later for the second cohort (4.3 years compared with 4.4 years) but otherwise performance indicators improved in the second cohort. Community orthoptists achieved a sensitivity of about 90% and specificity of 99% during the study. It is unlikely that the more commonly used two tier system of health visitors referring to a community orthoptist could achieve this degree of accuracy.