| axis opticus | The axis of the eye connecting the anterior and posterior poles; it usually diverges from the visual axis by five degrees or more. Synonym: axis opticus. (05 Mar 2000) |
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| axis pelvis | A hypothetical curved line joining the centre point of each of the four planes of the pelvis, marking the centre of the pelvic cavity at every level. Synonym: axis pelvis, plane of pelvic canal. (05 Mar 2000) |
| axis, principal | <microscopy> A line conceived as passing through the centre of a lens to connect the centres of curvature of the lens surfaces. The focal points of a lens lie on the principal axis. (05 Aug 1998) |
| axis shift | Deflection of the electrical axis of the heart to the right or left of the normal. See: left axis deviation, right axis deviation, axis. Synonym: axis shift. (05 Mar 2000) |
| axis traction | Rarely used procedure to apply traction upon the foetal head in the line of the birth canal by means of axis traction forceps. (05 Mar 2000) |
| axis-traction forceps | Obstetrical forceps provided with a second handle so attached that traction can be made in the line in which the head must move in the axis of the pelvis. (05 Mar 2000) |
| basibregmatic axis | A line extending from the basion to the bregma. (05 Mar 2000) |
| basicranial axis | A line drawn from the basion to the midpoint of the sphenoethmoidal suture. (05 Mar 2000) |
| basifacial axis | A line drawn from the subnasal point to the midpoint of the sphenoethmoidal suture. Synonym: facial axis. (05 Mar 2000) |
| biauricular axis | A straight line joining the two auricles. Compare: auriculare. (05 Mar 2000) |
| magnetic axis | <physics> This typically refers to the location of the innermost flux surface in a toroidal device, the one which encloses no volume and has therefore degenerated from a flux surface into a single field line. Roughly, the circle through the middle of the dough of the donut. Additionally, in systems with magnetic islands (see entry below), each island has a local magnetic axis, distinct from the overall magnetic axis of the torus. (09 Oct 1997) |
| mandibular axis | An imaginary line around which the mandible may rotate through the horizontal plane. Synonym: hinge axis, mandibular axis. (05 Mar 2000) |
| vertical axis | In dentistry, the line around which the working side condyle rotates in the horizontal plane during mandibular movement. (05 Mar 2000) |
| mean electrical axis | The average magnitude and direction of all the electromotive forces developed during the cardiac event under consideration; e.g., atrial or ventricular depolarisation, or ventricular repolarization. See: axis deviation. (05 Mar 2000) |
| visual axis | The straight line extending from the object seen, through the centre of the pupil, to the macula lutea of the retina. Synonym: line of vision. (05 Mar 2000) |