After determining the best spherical correction during subjective refraction, the examiner introduces the Jackson cross cylinder. Which parameter should be refined first with this lens?
- A Spherical power, before touching the cylinder
- B Power of the cylinder, followed by its axis
- C Axis of the correcting cylinder, followed by its power ✓
- D Near addition, using the cross cylinder at 40 cm
Correct answer: C. Axis of the correcting cylinder, followed by its power
Explanation
Standard JCC technique refines the cylinder axis first, using the straddle technique along the axis, because an incorrect axis invalidates any subsequent power check. Once the axis is confirmed, the cross cylinder is flipped to compare cylinder power adjustments. The JCC is a distance refraction tool used at the patient's best acuity level, not for measuring the near addition, and sphere refinement precedes introduction of the cross cylinder entirely.
Reference: Parsons' Diseases of the Eye, 23rd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.