Question:hard
Which of the following spectacle prescriptions is an example of Simple Myopic Astigmatism?
Which of the following spectacle prescriptions is an example of Simple Myopic Astigmatism?
Show Hint
Simple astigmatism = plano sphere + one cylinder; myopic means the cylinder is minus.
Updated On: Jun 23, 2026
- Rx (+) sphere
- Rx will be plano (-)
- Rx will be (-) sphere
- (-)(+) (+)(-) on both 90 and 180 degree axis
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Remember the rule for "simple" astigmatism: one meridian focuses on the retina, so its spherical power is plano, and a single cylinder corrects the second meridian.
Step 2: Attach the sign to the type of error. Myopic means the errant meridian needs minus power, so simple myopic astigmatism is written as $plano / (-)cyl$.
Step 3: Match against the choices. "$(+)$ sphere" is pure simple hyperopia and "$(-)$ sphere" is pure simple myopia - both are spherical, non-astigmatic. The opposite-sign meridional combination $(-)(+)$ / $(+)(-)$ is mixed astigmatism.
Step 4: Only "plano $(-)$" fits a plano sphere with a minus cylinder, which is exactly simple myopic astigmatism.
\[\boxed{\text{Rx will be plano (-)}}\]
Step 2: Attach the sign to the type of error. Myopic means the errant meridian needs minus power, so simple myopic astigmatism is written as $plano / (-)cyl$.
Step 3: Match against the choices. "$(+)$ sphere" is pure simple hyperopia and "$(-)$ sphere" is pure simple myopia - both are spherical, non-astigmatic. The opposite-sign meridional combination $(-)(+)$ / $(+)(-)$ is mixed astigmatism.
Step 4: Only "plano $(-)$" fits a plano sphere with a minus cylinder, which is exactly simple myopic astigmatism.
\[\boxed{\text{Rx will be plano (-)}}\]
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