Question
A patient’s refraction is +1.00 DS / −2.00 DC × 180°.
Which type of astigmatism does this represent?
| A. |
With the rule astigmatism
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| B. |
Against the rule astigmatism
|
| C. |
Simple astigmatism
|
| D. |
Mixed astigmatism
|
Show Answer
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Correct Answer » D
Explanation
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|
Prescription is in minus-cylinder form.
At 180° meridian:
+1.00 − 2.00 = −1.00 D → myopic
At 90° meridian:
+1.00 D → hypermetropic
So This defines mixed astigmatism.
With-the-rule astigmatism
→ This describes axis orientation, not refractive type.
Against-the-rule astigmatism
→ Axis here is 180° in minus-cylinder form → WTR, not ATR.
Simple astigmatism
→ Would require one meridian emmetropic and the other ametropic.
Here both meridians are ametropic.
