Jackson’s Cross Cylinder (JCC): The Best Guide for Optometrists

Jackson’s Cross Cylinder (JCC)

Jackson’s Cross Cylinder (JCC) is an essential tool in clinical refraction used to refine the cylinder power and axis in astigmatic patients. It plays a pivotal role in achieving optimal visual clarity and precision in spectacle prescriptions. This post will explore JCC in detail — its components, working principle, procedure, and interpretation — along with commonly asked interview questions.

What is Jackson’s Cross Cylinder (JCC)?

Jackson’s Cross Cylinder is a bitoric lens used to refine astigmatism correction during subjective refraction. It is mounted in a handle and consists of two equal but opposite cylindrical powers at perpendicular axes, such as:

• +0.25 D / -0.25 D
• +0.50 D / -0.50 D

This means one axis is plus and the axis 90° away is minus.

Purpose of JCC

JCC is mainly used to:

• Refine the cylinder axis.
• Refine the cylinder power.
• Confirm the correctness of astigmatic correction.

Structure of JCC

• Two cylindrical lenses of equal magnitude but opposite signs.
• Markings at the handle: red (minus cylinder axis), white (plus cylinder axis).
• Rotatable handle for easy flipping between positions.

How JCC Works

When the JCC lens is flipped, it reverses the plus and minus axes. The patient compares the clarity of vision in each flip. The optometrist then adjusts the axis or power based on the patient’s response.

Steps of Using JCC in Refraction

1. Cylinder Axis Refinement

• Align the JCC axis with the axis of the correcting cylinder.
• Ask the patient: “Which is better — position one or two?”
• If the patient prefers the flipped position, rotate the cylinder axis in that direction by 5–10 degrees.
• Repeat until no preference.

2. Cylinder Power Refinement

• Place the JCC with its axes at 45° to the correcting cylinder axis.
• Ask: “Which is clearer?”
• If patient prefers minus axis side (red), increase cylinder power by -0.25 D.
• If they prefer plus axis (white), decrease by 0.25 D.
• Adjust the sphere power accordingly to maintain spherical equivalent.

Spherical Equivalent Compensation

For every -0.50 D added in cylinder power:

• Add +0.25 D to the sphere to maintain spherical equivalent.

Example:
Initial Rx: -1.00 DS / -0.50 DC × 180
If cylinder changed to -1.00 DC, sphere becomes -0.75 DS

Clinical Tips

• Use JCC after best spherical correction.
• Ensure patient is well-instructed about what to look for (clarity, sharpness).
• In older or confused patients, make changes based on confidence in responses.
• Consider binocular balancing afterward for final prescription.

Common JCC Powers

• ±0.25 D — used for fine-tuning.
• ±0.50 D — used in initial cylinder estimation.