Practice Quiz

Certified Ophthalmic Medical Technologist (COMT)

Category - COMT

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Which of these reflects the following prescription:  +1.00 +3.00 x 90 correctly transposed to minus cylinder?

  1. +1.00 -3.00 x 180
  2. -1.00 -3.00 x 90
  3. +4.00 -3.00 x 180
  4. -4.00 -3.00 x 90
Explanation

Answer: C - +4.00 -3.00 x 180 correctly transposes the prescription to minus cylinder.

Since lenses come in minus cylinder, all plus cylinder prescriptions must be transposed. This is done by adding the sphere and cylinder together, changing the sign of the cylinder, then changing the axis by a factor of 90º.

+1.00 +3.00 x 90 = (+1.00 +3.00) -3.00 x (90 +90) = +4.00 -3.00 x 180

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