4 Topic Commentaries

Defusing the Confusion of the Jackson Cross Cylinder

• 

  Richard J. Kolker, MD

  Ophthalmology (Clinical Refraction)

  •

  The Wilmer Eye Institute, The Johns Hopkins Hospital

  The correct cylinder axis has been located when the cross cylinder is flipped and the two choices are equally clear.

  Source
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  Mark E. Wilkinson, OD, FAAO

  Optometry and Low Vision Rehabilitation

  •

  University of Iowa Carver College of Medicine

  Cross cylinders are combinations of two cylinders whose powers are numerically equal and of opposite sign and whose axes are perpendicular to each other. The Jackson Cross Cylinder is usually mounted in a ring with a handle at 45 degrees from the axis so that a twirl of the handle changes the cross cylinder to a second position.

  Source
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  Khadija S. Shahid, OD, MPH, FAAO

  Optometry

  •

  University of Iowa Carver College of Medicine

  Answer: Parallel. To define the astigmatic power, the handle is rotated 45 degrees to the axis. Normally, you should define the axis before the power.

  Source
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  Phillips Thygeson, MD

  Ophthalmology (External Eye Disease; Physiological Optics)

  •

  University of California, San Francisco

  He taught me cross-cylinder, which was a wonderful technique at that time, but hardly anybody knew it except Jackson.

  Source