Eye axis

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The definition of eye axes in ophthalmology and optics includes a series of imaginary connecting lines between two or more points inside or outside the eye . They serve as an orientation for certain diagnostic purposes or when making optical corrections. The terminology used is based on different sources and is therefore not always uniform. In the case of astigmatism, for example, the angle between the plane of incidence and the horizontal plane is sometimes incorrectly referred to as the “eye axis”. The following definitions of eye axes are described in the literature:

  • The anatomical axis denotes the straight line between the anterior and posterior poles of the eyeball, more precisely: between the center of the cornea and the center of curvature of the posterior segment of the eye. This definition also corresponds to the overall length of the eye, which is used to determine axial refractive errors .
  • The optical axis is the straight line between the centers of curvature of refractive surfaces in a centered system.
  • The visual axis is an axis that runs from the fovea centralis through the node of the eye to the fixation object.
  • The line of sight is the straight line between the foveola and Fixierobjekt.
  • The line of sight is the straight line between the pivot point of the eye and the object to be fixed.
  • The pupil axis denotes the straight line between the center of the cornea and the center of the pupil.

There is a relationship between individual eye axes with regard to their course, which are defined using the following terms:

  • Angle alpha - denotes the angle between the optical axis and the line of sight
  • Angle Gamma - describes the angle between the optical axis and the line of sight
  • Angle Kappa - describes the angle between the line of sight and the pupil axis.

The knowledge of the respective deviations of the axes from one another is used in strabological diagnostics when assessing corneal reflex images and thus the eye position. In particular, the consideration of the kappa angle to identify a pseudo-strabismus is relevant.

Individual evidence

  1. ↑ Jack J. Kanski: Clinical Ophthalmology . Elsevier, Urban & Fischer, Munich 2008, ISBN 978-3-437-23471-2 , pp. 754 .

literature