A spherical RGP lens bearing on the eye shows a vertical dumbbell shape. This indicates which astigmatism orientation?

Study for the NBEO Physiological Optics Test. Prepare with flashcards and multiple-choice questions, each question has hints and explanations. Ace your exam!

Multiple Choice

A spherical RGP lens bearing on the eye shows a vertical dumbbell shape. This indicates which astigmatism orientation?

Explanation:
The pattern seen on the back of a spherical RGP lens reflects which corneal meridian is steeper. The lens bears more where the cornea has greater curvature, so the orientation of the bearing pattern tells you which meridian is steep. A vertical dumbbell pattern means the lens is bearing more in the horizontal direction, indicating the horizontal meridian is the steep one. The horizontal steepness corresponds to against-the-rule astigmatism, where the axis is vertical. So this vertical dumbbell implies ATR.

The pattern seen on the back of a spherical RGP lens reflects which corneal meridian is steeper. The lens bears more where the cornea has greater curvature, so the orientation of the bearing pattern tells you which meridian is steep. A vertical dumbbell pattern means the lens is bearing more in the horizontal direction, indicating the horizontal meridian is the steep one. The horizontal steepness corresponds to against-the-rule astigmatism, where the axis is vertical. So this vertical dumbbell implies ATR.

More Multiple Choice Questions
Subscribe

Get the latest from Passetra

You can unsubscribe at any time. Read our privacy policy