During subjective refraction, the Jackson cross cylinder is used primarily to:
- A Detect the presence of astigmatism before retinoscopy
- B Measure the amplitude of accommodation
- C Refine the axis and then the power of the correcting cylinder ✓
- D Determine the dominant eye
Correct answer: C. Refine the axis and then the power of the correcting cylinder
Explanation
The Jackson cross cylinder is a lens combining equal and opposite cylinders, for example +0.25 DC and -0.25 DC, with axes 90 degrees apart, mounted on a flipping handle. It is used after the initial cylinder has been estimated to refine the cylinder axis first, then the cylinder power, by comparing the clarity of the two flip positions. Detection of astigmatism is done by retinoscopy or keratometry, and accommodation amplitude requires other methods.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.