This study was designed to investigate the relationship between the as
tigmatic axes of right and left eye pairs, with particular attention g
iven to determining the degree to which either direct or mirror symmet
ry (enantiomorphism) of the astigmatic axes exists. A sample of 192 ''
nonvisually'' selected adults participated, with refractive error and
corneal curvature data being measured using autokerato-refractive equi
pment. Total, corneal, and residual astigmatism were investigated, wit
h residual astigmatism being taken as the vector difference between to
tal and corneal astigmatism. There was no evidence for a predominance
of either mirror or direct symmetry of the astigmatic axes within this
sample. The patterns of astigmatic axis distribution of right and lef
t eyes were remarkably similar but, within this context, there was no
definite evidence for a definable association between the axis of the
left and right pairs of individuals. These findings remained unchanged
when the effect of the modulus of astigmatism was incorporated, eithe
r through weighting the frequency distributions or through analyzing a
subgroup of the overall population (those individuals with greater th
an 0.50 D of astigmatism). We believe these findings contradict common
ly held clinical impressions regarding the symmetry of astigmatic axes
, and should be considered when performing statistical analysis of ast
igmatic data.