topography

• The geometric equator is a circle around the external surface of a sphere equidistant from the two poles
• The anatomic equator is equidistant to the actual poles of the eye and is tilted backward on the temporal side and forward nasally
• The anterior segment of the eye includes the ciliary body, lens, cornea, and part of the sclera
• The visual axis is the projection of the foveal center into object space through the eye's nodal points
• The line of sight is between an external object of regard and the center of the entrance pupil
• The pupillary axis is a line perpendicular to the cornea at its apex that passes through the center of the eye's entrance pupil
• The optic axis is a line passing through the center of the anterior and posterior curves of the cornea and the lens and the principal, focal, and nodal points
• The fixation axis connects the center of rotation to the point of fixation and lies near the visual axis but does not pass through the nodal points
• The visual field is the area or extent of physical space to an eye in a given position