The Visual Axis is one of the axes through
the eye that is a useful construct for optical equipment designers and
those working with the physics / optics rather than the biology / physiology
of human vision.
Note that this is not a physical feature of the eye and so
cannot be identified by dissection or by any physical imaging techniques.
A simple definition of the visual axis is:
" A straight line that passes through both the centre
of the pupil and the centre of the fovea".
There is also a stricter definition (in terms of nodal points) which
is important for specialists in optics and related subjects.
Other axes through the eye include the Geometrical
The subject of visual (also known as "physiological") optics
is a key component of many courses within the fields of both biology and
physics. It is also an essential consideration in the design of displays
and control units used in many applications from televisions and mobile
telephones to advanced aircraft. In the context of engineering "visual
optics" is one of several medical and psychological topics in the
important area of "Human Factors".