Question
A patient’s refraction is +1.00 DS / −2.00 DC × 180°.
Which type of astigmatism does this represent?
Which type of astigmatism does this represent?
| A. |
With the rule astigmatism |
| B. |
Against the rule astigmatism |
| C. |
Simple astigmatism |
| D. |
Mixed astigmatism |
Show Answer
|
Correct Answer » D Explanation |
 |
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.