Practice Quiz

Ophthalmic Assistant

Category - Keratometry, Tonometry, and Refractometry

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“Against the rule”refers to the corneal astigmatism when
  1. the horizontal meridian is flatter than the vertical meridian.
  2. the horizontal meridian is steeper than the vertical meridian.
  3. the corneal astigmatism from the eye differs from that of the refractive cylinder of the prescription.
  4. none of the above.
Explanation
Answer: B - the horizontal meridian is steeper than the vertical meridian.
“Against the rule” refers to the corneal astigmatism when the horizontal meridian is steeper than the vertical meridian. Conversely, “with the rule” refers to the corneal astigmatism when the horizontal meridian is flatter than the vertical meridian.
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