Application of multivariate analysis of vari-ance (MANOVA) to distance refractive vari-ability and mean distance refractive state

Abstract

Refractive state can be regarded as a dynam-ic quantity. Multiple measurements of refractive state can be determined easily and rapidly on a number of different occasions using an autore-fractor. In an experimental trial undertaken by Gillan, a 30-year-old female was subjected to 30 autorefractor measurements each taken at vari-ous intervals before and after the instillation of Mydriacyl 1% (tropicamide) into her right eye. The purpose of this paper is to apply multivar-iate analysis of variance (MANOVA) to Gillan’s sample data in order to assess whether instillation of Mydriacyl into the eye affects variability of distance refractive state as well as mean distance refractive state as measured by an autorefractor. In  five  of  the  seven  cases  where  pairwise hypotheses  tests  were  performed,  it  is  con-cluded that at a 99% level of confidence there is no difference in variability of distance refrac-tive state before and after cycloplegia. In two of the three cases where MANOVA was applied, there is a significant difference at a 95% and at a 99% level of confidence in both variability of distance refractive state and mean distance refractive  state  with  and  without  cycloplegia.