Accommodation Values in a Normal Sydney Population, is the RAF Rule Still Valid?
Elaine Cornell, DOBA DipAppSc (Cumb)MA(Macq)
Robert Heard, PhD(Syd)
The evaluation of the dynamic components of the near response forms a major part of an assessment of a person who has symptoms for near, or who has difficulty in changing focus. The close association of accommodation with age means that measures obtained in a clinical assessment must be compared with age related normal values to determine whether or not any abnormality is present.
In Australia, the most commonly used instrument to assess accommodation is the RAF rule. This instrument has the advantage of being able to determine the amount of accommodation occurring ( in dioptres) and to match this against age related values. It also enable a simple measurement of the accommodation and convergence near point (in cms). The ‘normal’ values indicated on this device are those determined by Duane in 1912. These are taken from a comprehensive study of normal accommodation, where the near blue point was measured and converted to diopters, assuming that any refractive error was corrected. It is likely that the ‘mean’ values are actually median values as they are always exactly midway between the upper and lower values.
Clinical norms must be matched to those of the relevant population, and, in an urban Australia society at the end of the 20th century, the question must be asked as to whether values determined over eighty five years ago are still appropriate to use as normal for our population.