A patient's refraction is recorded as +3.00 / -2.00 × 90. The axis 90° means the minus cylinder axis is vertical. What type of astigmatism is this?
- A Compound hypermetropic astigmatism — against-the-rule ✓
- B Simple myopic astigmatism
- C Compound hypermetropic astigmatism — with-the-rule
- D Mixed astigmatism
Explanation
The prescription +3.00 / -2.00 × 90 has two principal meridians: the vertical meridian (90°) has power +3.00 - 2.00 = +1.00 D, and the horizontal meridian (180°) has power +3.00 D. Both meridians are positive (hypermetropic), so this is compound hypermetropic astigmatism. In with-the-rule astigmatism (the common type in youth), the vertical meridian has greater refracting power, meaning the minus cylinder axis is at 180°. Here the minus cylinder axis is at 90° (vertical), indicating greater horizontal corneal power — this is against-the-rule astigmatism. Mixed astigmatism requires one meridian to be myopic (minus) and the other hypermetropic (plus). Simple astigmatism requires one meridian to be emmetropic (plano).
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.